bims-lysosi 2021-04-11 papers

bims-lysosi

Biomed News

on Lysosomes and signaling

Issue of 2021–04–11
thirty-one papers selected by
Stephanie Fernandes, Max Planck Institute for Biology of Ageing

ATP6V0A1 encoding the a1-subunit of the V0 domain of vacuolar H+-ATPases is essential for brain development in humans and mice.
PLD3 is a neuronal lysosomal phospholipase D associated with β-amyloid plaques and cognitive function in Alzheimer's disease.
Glucose restriction drives spatial reorganization of mevalonate metabolism.
LAPTM4α is targeted from the Golgi to late endosomes/lysosomes in a manner dependent on the E3 ubiquitin ligase Nedd4-1 and ESCRT proteins.
TSC-insensitive Rheb mutations induce oncogenic transformation through a combination of constitutively active mTORC1 signalling and proteome remodelling.
Lysosome dysfunction as a cause of neurodegenerative diseases: Lessons from frontotemporal dementia and amyotrophic lateral sclerosis.
The paradox of autophagy in Tuberous Sclerosis Complex.
PI3K/AKT/mTOR signalling pathway involvement in renal cell carcinoma pathogenesis (Review).
A TOR (target of rapamycin) and nutritional phosphoproteome of fission yeast reveals novel targets in networks conserved in humans.
CCCP-induced mitochondrial dysfunction: Characterization and analysis of integrated stress response to cellular signaling and homeostasis.
Reduction in miR-219 expression underlies cellular pathogenesis of oligodendrocytes in a mouse model of Krabbe disease.
MCOLN1 gene therapy corrects neurologic dysfunction in the mouse model of mucolipidosis IV.
Sex-dependent lifespan extension of Apc Min/+ FAP mice by chronic mTOR inhibition.
AMPK/ULK1-mediated phosphorylation of Parkin ACT domain mediates an early step in mitophagy.
PIKfyve activity is required for lysosomal trafficking of tau aggregates and tau seeding.
Diverse nitrogen signals activate convergent ROP2-TOR signaling in Arabidopsis.
Regulatory Mechanisms of Autophagy-Targeted Antimicrobial Therapeutics Against Mycobacterial Infection.
Unveiling the Dynamics of KRAS4b on Lipid Model Membranes.
The Mechanisms of L-Arginine Metabolism Disorder in Endothelial Cells.
Over-expressed RHEB promotes the progression of pancreatic adenocarcinoma.
The interplay between Glucocerebrosidase, α-synuclein and lipids in human models of Parkinson's disease.
A unique C2 domain at the C terminus of Munc13 promotes synaptic vesicle priming.
Aminoacyl-tRNA synthetases in cell signaling.
Cell-programmed nutrient partitioning in the tumour microenvironment.
Lysosome-targeted photodynamic treatment induces primary keratinocyte differentiation.
Signaling Pathways Involved in Nutrient Sensing Control in Cancer Stem Cells: An Overview.
Rab2 regulates presynaptic precursor vesicle biogenesis at the trans-Golgi.
Intracellular mRNA transport and localized translation.
Organelle homeostasis principles: How organelle quality control and inter-organelle crosstalk promote cell survival.
The m6A RNA methylation regulates oncogenic signaling pathways driving cell malignant transformation and carcinogenesis.
Oncogenic role of MiR-130a in oral squamous cell carcinoma.

Nat Commun. 2021 04 08. 12(1): 2107

ATP6V0A1 encoding the a1-subunit of the V0 domain of vacuolar H+-ATPases is essential for brain development in humans and mice.

Kazushi Aoto, Mitsuhiro Kato, Tenpei Akita, Mitsuko Nakashima, Hiroki Mutoh, Noriyuki Akasaka, Jun Tohyama, Yoshiko Nomura, Kyoko Hoshino, Yasuhiko Ago, Ryuta Tanaka, Orna Epstein, Revital Ben-Haim, Eli Heyman, Takehiro Miyazaki, Hazrat Belal, Shuji Takabayashi, Chihiro Ohba, Atsushi Takata, Takeshi Mizuguchi, Satoko Miyatake, Noriko Miyake, Atsuo Fukuda, Naomichi Matsumoto, Hirotomo Saitsu.

Vacuolar H+-ATPases (V-ATPases) transport protons across cellular membranes to acidify various organelles. ATP6V0A1 encodes the a1-subunit of the V0 domain of V-ATPases, which is strongly expressed in neurons. However, its role in brain development is unknown. Here we report four individuals with developmental and epileptic encephalopathy with ATP6V0A1 variants: two individuals with a de novo missense variant (R741Q) and the other two individuals with biallelic variants comprising one almost complete loss-of-function variant and one missense variant (A512P and N534D). Lysosomal acidification is significantly impaired in cell lines expressing three missense ATP6V0A1 mutants. Homozygous mutant mice harboring human R741Q (Atp6v0a1R741Q) and A512P (Atp6v0a1A512P) variants show embryonic lethality and early postnatal mortality, respectively, suggesting that R741Q affects V-ATPase function more severely. Lysosomal dysfunction resulting in cell death, accumulated autophagosomes and lysosomes, reduced mTORC1 signaling and synaptic connectivity, and lowered neurotransmitter contents of synaptic vesicles are observed in the brains of Atp6v0a1A512P/A512P mice. These findings demonstrate the essential roles of ATP6V0A1/Atp6v0a1 in neuronal development in terms of integrity and connectivity of neurons in both humans and mice.

DOI: https://doi.org/10.1038/s41467-021-22389-5
PLoS Genet. 2021 Apr;17(4): e1009406

PLD3 is a neuronal lysosomal phospholipase D associated with β-amyloid plaques and cognitive function in Alzheimer's disease.

Alex G Nackenoff, Timothy J Hohman, Sarah M Neuner, Carolyn S Akers, Nicole C Weitzel, Alena Shostak, Shawn M Ferguson, Bret Mobley, David A Bennett, Julie A Schneider, Angela L Jefferson, Catherine C Kaczorowski, Matthew S Schrag.

Phospholipase D3 (PLD3) is a protein of unclear function that structurally resembles other members of the phospholipase D superfamily. A coding variant in this gene confers increased risk for the development of Alzheimer's disease (AD), although the magnitude of this effect has been controversial. Because of the potential significance of this obscure protein, we undertook a study to observe its distribution in normal human brain and AD-affected brain, determine whether PLD3 is relevant to memory and cognition in sporadic AD, and to evaluate its molecular function. In human neuropathological samples, PLD3 was primarily found within neurons and colocalized with lysosome markers (LAMP2, progranulin, and cathepsins D and B). This colocalization was also present in AD brain with prominent enrichment on lysosomal accumulations within dystrophic neurites surrounding β-amyloid plaques. This pattern of protein distribution was conserved in mouse brain in wild type and the 5xFAD mouse model of cerebral β-amyloidosis. We discovered PLD3 has phospholipase D activity in lysosomes. A coding variant in PLD3 reported to confer AD risk significantly reduced enzymatic activity compared to wild-type PLD3. PLD3 mRNA levels in the human pre-frontal cortex inversely correlated with β-amyloid pathology severity and rate of cognitive decline in 531 participants enrolled in the Religious Orders Study and Rush Memory and Aging Project. PLD3 levels across genetically diverse BXD mouse strains and strains crossed with 5xFAD mice correlated strongly with learning and memory performance in a fear conditioning task. In summary, this study identified a new functional mammalian phospholipase D isoform which is lysosomal and closely associated with both β-amyloid pathology and cognition.

DOI: https://doi.org/10.1371/journal.pgen.1009406
Elife. 2021 Apr 07. pii: e62591. [Epub ahead of print]10

Glucose restriction drives spatial reorganization of mevalonate metabolism.

Sean M Rogers, Hanaa Hariri, N Ezgi M Wood, Natalie Ortiz Speer, W Mike Henne.

  Eukaryotes compartmentalize metabolic pathways into sub-cellular domains, but the role of inter-organelle contacts in organizing metabolic reactions remains poorly understood. Here, we show that in response to acute glucose restriction (AGR) yeast undergo metabolic remodeling of their mevalonate pathway that is spatially coordinated at nucleus-vacuole junctions (NVJs). The NVJ serves as a metabolic platform by selectively retaining HMG-CoA Reductases (HMGCRs), driving mevalonate pathway flux in an Upc2-dependent manner. Both spatial retention of HMGCRs and increased mevalonate pathway flux during AGR is dependent on NVJ tether Nvj1. Furthermore, we demonstrate that HMGCRs associate into high molecular weight assemblies during AGR in an Nvj1-dependent manner. Loss of Nvj1-mediated HMGCR partitioning can be bypassed by artificially multimerizing HMGCRs, indicating NVJ compartmentalization enhances mevalonate pathway flux by promoting the association of HMGCRs in high molecular weight assemblies. Loss of HMGCR compartmentalization perturbs yeast growth following glucose starvation, indicating it promotes adaptive metabolic remodeling. Collectively we propose a non-canonical mechanism regulating mevalonate metabolism via the spatial compartmentalization of rate-limiting HMGCR enzymes at an inter-organelle contact site.

Keywords:  S. cerevisiae; cell biology

DOI:  https://doi.org/10.7554/eLife.62591
Biochem Biophys Res Commun. 2021 Apr 06. pii: S0006-291X(21)00562-3. [Epub ahead of print]556 9-15

LAPTM4α is targeted from the Golgi to late endosomes/lysosomes in a manner dependent on the E3 ubiquitin ligase Nedd4-1 and ESCRT proteins.

Yuko Hirota, Masaharu Hayashi, Yuu Miyauchi, Yuji Ishii, Yoshitaka Tanaka, Keiko Fujimoto.

  Lysosome-associated protein transmembrane 4α (LAPTM4α) is a four transmembrane-spanning protein primarily localized in endosomes and lysosomes and has several putative lysosomal targeting signals at its C-terminal cytoplasmic domain, including tyrosine-based motifs (YxxΦ) and PY motifs (L/PxxY). LAPTM4α has been previously shown to be ubiquitinated by the E3 ubiquitin ligase Nedd4-1 through binding to its PY motifs and sorted to lysosomes, however, the molecular mechanisms underlying the localization of LAPTM4α to endosomes/lysosomes have not yet been fully elucidated. In the present study, we show that LAPTM4α binds Nedd4-1 in a manner dependent on PY motifs, while the PY motifs and Nedd4-1 are not necessarily required for LAPTM4α ubiquitination. The binding of LAPTM4α with Nedd4-1, however, is necessary for an effective sorting of LAPTM4α from the Golgi to late endosomes/lysosomes. An unexpected finding is that LAPTM4α is localized in the lumen, but not in the limiting membrane, of late endosomes, and degraded in lysosomes over time. Interestingly, we further found that siRNA knockdown of endosomal sorting complexes required for transport (ESCRT) components that mediate sorting of ubiquitinated membrane proteins into intralumenal vesicles (ILVs) of endosomes selectively blocks the transport of LAPTM4α to endosomes. Collectively, these results suggest that trafficking of LAPTM4α from the Golgi to endosomes is promoted by the interaction with Nedd4-1, which further requires ESCRT components. Furthermore, our findings highlight a novel function for ESCRT proteins in mediating protein and/or vesicle trafficking from the Golgi to endosomes/lysosomes.

Keywords:  ESCRT; Lysosomal membrane; Nedd4-1; Ubiquitination

DOI:  https://doi.org/10.1016/j.bbrc.2021.03.151
Cell Mol Life Sci. 2021 Apr 08.

TSC-insensitive Rheb mutations induce oncogenic transformation through a combination of constitutively active mTORC1 signalling and proteome remodelling.

Jianling Xie, Stuart P De Poi, Sean J Humphrey, Leanne K Hein, John B Bruning, Wenru Pan, Luke A Selth, Timothy J Sargeant, Christopher G Proud.

  The mechanistic target of rapamycin complex 1 (mTORC1) is an important regulator of cellular metabolism that is commonly hyperactivated in cancer. Recent cancer genome screens have identified multiple mutations in Ras-homolog enriched in brain (Rheb), the primary activator of mTORC1 that might act as driver oncogenes by causing hyperactivation of mTORC1. Here, we show that a number of recurrently occurring Rheb mutants drive hyperactive mTORC1 signalling through differing levels of insensitivity to the primary inactivator of Rheb, tuberous sclerosis complex. We show that two activated mutants, Rheb-T23M and E40K, strongly drive increased cell growth, proliferation and anchorage-independent growth resulting in enhanced tumour growth in vivo. Proteomic analysis of cells expressing the mutations revealed, surprisingly, that these two mutants promote distinct oncogenic pathways with Rheb-T23M driving an increased rate of anaerobic glycolysis, while Rheb-E40K regulates the translation factor eEF2 and autophagy, likely through differential interactions with 5' AMP-activated protein kinase (AMPK) which modulate its activity. Our findings suggest that unique, personalized, combination therapies may be utilised to treat cancers according to which Rheb mutant they harbour.

Keywords:  AMPK; PKM; Rheb; TSC; eEF2; mTOR

DOI:  https://doi.org/10.1007/s00018-021-03825-7
Neurobiol Dis. 2021 Mar 31. pii: S0969-9961(21)00109-1. [Epub ahead of print] 105360

Lysosome dysfunction as a cause of neurodegenerative diseases: Lessons from frontotemporal dementia and amyotrophic lateral sclerosis.

Jessica Root, Paola Merino, Austin Nuckols, Michelle Johnson, Thomas Kukar.

  Frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) are fatal neurodegenerative disorders that are thought to exist on a clinical and pathological spectrum. FTD and ALS are linked by shared genetic causes (i.e. C9orf72 hexanucleotide repeat expansions) and neuropathology, such as inclusions of ubiquitinated, misfolded proteins (i.e. TAR DNA-binding protein 43; TDP-43) in the CNS. Furthermore, some genes that cause FTD or ALS when mutated encode proteins that localize to the lysosome or modulate endosome-lysosome function, including lysosomal fusion, cargo trafficking, lysosomal acidification, autophagy, or TFEB activity. In this review, we summarize evidence that lysosomal dysfunction, caused by genetic mutations (i.e. C9orf72, GRN, MAPT, TMEM106B) or toxic-gain of function (i.e. aggregation of TDP-43 or tau), is an important pathogenic disease mechanism in FTD and ALS. Further studies into the normal function of many of these proteins are required and will help uncover the mechanisms that cause lysosomal dysfunction in FTD and ALS. Mutations or polymorphisms in genes that encode proteins important for endosome-lysosome function also occur in other age-dependent neurodegenerative diseases, including Alzheimer's (i.e. APOE, PSEN1, APP) and Parkinson's (i.e. GBA, LRRK2, ATP13A2) disease. A more complete understanding of the common and unique features of lysosome dysfunction across the spectrum of neurodegeneration will help guide the development of therapies for these devastating diseases.

Keywords:  Alzheimer's disease and related dementias (ADRD); Amyotrophic lateral sclerosis (ALS); Autophagy; C9orf72; Frontotemporal dementia (FTD); Frontotemporal lobar degeneration (FTLD); Granulins (GRNs); Lysosome dysfunction; Microtubule-associated protein tau (MAPT); Neurodegeneration; Progranulin (PGRN); Transactive response DNA binding protein 43 kDa (TDP-43); Transcription factor EB (TFEB); Transmembrane protein 106B (TMEM106B); Ubiquitin

DOI:  https://doi.org/10.1016/j.nbd.2021.105360
Genet Mol Biol. 2021 ;pii: S1415-47572021000300103. [Epub ahead of print]44(2): e20200014

The paradox of autophagy in Tuberous Sclerosis Complex.

Larissa Brussa Reis, Eduardo C Filippi-Chiela, Patricia Ashton-Prolla, Fernanda Visioli, Clévia Rosset.

Tuberous sclerosis complex (TSC) is an autosomal dominant genetic disorder caused by germline mutations in TSC1 or TSC2 genes, which leads to the hyperactivation of the mTORC1 pathway, an important negative regulator of autophagy. This leads to the development of hamartomas in multiple organs. The variability in symptoms presents a challenge for the development of completely effective treatments for TSC. One option is the treatment with mTORC1 inhibitors, which are targeted to block cell growth and restore autophagy. However, the therapeutic effect of rapamycin seems to be more efficient in the early stages of hamartoma development, an effect that seems to be associated with the paradoxical role of autophagy in tumor establishment. Under normal conditions, autophagy is directly inhibited by mTORC1. In situations of bioenergetics stress, mTORC1 releases the Ulk1 complex and initiates the autophagy process. In this way, autophagy promotes the survival of established tumors by supplying metabolic precursors during nutrient deprivation; paradoxically, excessive autophagy has been associated with cell death in some situations. In spite of its paradoxical role, autophagy is an alternative therapeutic strategy that could be explored in TSC. This review compiles the findings related to autophagy and the new therapeutic strategies targeting this pathway in TSC.

DOI: https://doi.org/10.1590/1678-4685-GMB-2020-0014
Exp Ther Med. 2021 May;21(5): 540

PI3K/AKT/mTOR signalling pathway involvement in renal cell carcinoma pathogenesis (Review).

Daniela Miricescu, Daniela Gabriela Balan, Adrian Tulin, Ovidiu Stiru, Ileana Adela Vacaroiu, Doina Andrada Mihai, Cristian Constantin Popa, Raluca Ioana Papacocea, Mihaly Enyedi, Nedelea Andrei Sorin, Guenadiy Vatachki, Dragoș Eugen Georgescu, Adriana Elena Nica, Constantin Stefani.

  Renal cell carcinoma (RCC) accounts for over 90% of all renal malignancies, and mainly affects the male population. Obesity and smoking are involved in the pathogenesis of several systemic cancers including RCC. The phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signalling pathway regulates cell growth, differentiation, migration, survival, angiogenesis, and metabolism. Growth factors, hormones, cytokine and many extracellular cues activate PI3K/AKT/mTOR. Dysregulation of this molecular pathway is frequently reported in human cancers including RCC and is associated with aggressive development and poor survival rate. mTOR is the master regulator of cell metabolism and growth, and is activated in many pathological processes such as tumour formation, insulin resistance and angiogenesis. mTOR inhibitors are used at present as drug therapy for RCC to inhibit cell proliferation, growth, survival, and the cell cycle. Temsirolimus and everolimus are two mTOR inhibitors that are currently used for the treatment of RCC. Drugs targeting the PI3K/AKT/mTOR signalling pathway may be one of the best therapeutic options for RCC.

Keywords:  hyperactivation; mTOR inhibitors; renal cell carcinoma; risk factors; signalling pathway; tumour progression

DOI:  https://doi.org/10.3892/etm.2021.9972
Open Biol. 2021 Apr;11(4): 200405

A TOR (target of rapamycin) and nutritional phosphoproteome of fission yeast reveals novel targets in networks conserved in humans.

Lenka Halova, David Cobley, Mirita Franz-Wachtel, Tingting Wang, Kaitlin R Morrison, Karsten Krug, Nicolas Nalpas, Boris Maček, Iain M Hagan, Sean J Humphrey, Janni Petersen.

  Fluctuations in TOR, AMPK and MAP-kinase signalling maintain cellular homeostasis and coordinate growth and division with environmental context. We have applied quantitative, SILAC mass spectrometry to map TOR and nutrient-controlled signalling in the fission yeast Schizosaccharomyces pombe. Phosphorylation levels at more than 1000 sites were altered following nitrogen stress or Torin1 inhibition of the TORC1 and TORC2 networks that comprise TOR signalling. One hundred and thirty of these sites were regulated by both perturbations, and the majority of these (119) new targets have not previously been linked to either nutritional or TOR control in either yeasts or humans. Elimination of AMPK inhibition of TORC1, by removal of AMPKα (ssp2::ura4+), identified phosphosites where nitrogen stress-induced changes were independent of TOR control. Using a yeast strain with an ATP analogue-sensitized Cdc2 kinase, we excluded sites that were changed as an indirect consequence of mitotic control modulation by nitrogen stress or TOR signalling. Nutritional control of gene expression was reflected in multiple targets in RNA metabolism, while significant modulation of actin cytoskeletal components points to adaptations in morphogenesis and cell integrity networks. Reduced phosphorylation of the MAPKK Byr1, at a site whose human equivalent controls docking between MEK and ERK, prevented sexual differentiation when resources were sparse but not eliminated.

Keywords:  Byr1 MAPKK; TORC1; TORC2; fission yeast Schizosaccharomyces pombe; nitrogen stress; phosphoproteome

DOI:  https://doi.org/10.1098/rsob.200405
FEBS J. 2021 Apr 09.

CCCP-induced mitochondrial dysfunction: Characterization and analysis of integrated stress response to cellular signaling and homeostasis.

Koncha Ramagopal Reddy, Gayatri Ramachandran, Naresh Babu V Sepuri, Kolluru V A Ramaiah.

  Mitochondrial dysfunction mediated by CCCP (carbonyl cyanide m-chlorophenyl hydrazone), an inhibitor of mitochondrial oxidative phosphorylation, evokes the integrated stress response (ISR), which is analyzed here by eIF2α phosphorylation and expression profiles of ATF4 and CHOP proteins. Our findings suggest that the CCCP-induced ISR pathway is mediated by activation of HRI kinase, but not by GCN2, PERK, or PKR. Also, CCCP activates AMPK, a cellular energy sensor, and AKT, a regulator implicated in cell survival, and suppresses phosphorylation of mTORC1 substrates eIF4E-BP1 and S6K. CCCP also downregulates translation and promotes autophagy, leading to non-caspase-mediated cell death in HepG2 cells. All these events are neutralized by NAC, an anti-ROS, suggesting that CCCP-induced mitochondrial dysfunction promotes oxidative stress. ISRIB, an inhibitor of the ISR pathway, mitigates CCCP-induced expression of ATF4 and CHOP, activation of AKT, and autophagy, similar to NAC. However, it fails to reverse CCCP-induced AMPK activation, suggesting that CCCP-induced autophagy is dependent on ISR and independent of AMPK activation. ISRIB restores partly, inhibition in eIF4E-BP1 phosphorylation, promotes eIF2α phosphorylation, albeit slowly, and mitigates suppression of translation accordingly, in CCCP-treated cells. These findings are consistent with the idea that CCCP-induced oxidative stress leading to eIF2α phosphorylation and ATF4 expression, which is known to stimulate genes involved in autophagy, play a pro-survival role together with AKT activation and regulate mTOR-mediated eIF4E-BP1 phosphorylation.

Keywords:  AKT; AMPK; ISRIB; Mitochondrial dysfunction; UPR; eIF4E-BP1

DOI:  https://doi.org/10.1111/febs.15868
Brain Pathol. 2021 Apr 06. e12951

Reduction in miR-219 expression underlies cellular pathogenesis of oligodendrocytes in a mouse model of Krabbe disease.

Naoko Inamura, Shinji Go, Takashi Watanabe, Hiroshi Takase, Nobuyuki Takakura, Atsuo Nakayama, Hirohide Takebayashi, Junko Matsuda, Yasushi Enokido.

  Krabbe disease (KD), also known as globoid cell leukodystrophy, is an inherited demyelinating disease caused by the deficiency of lysosomal galactosylceramidase (GALC) activity. Most of the patients are characterized by early-onset cerebral demyelination with apoptotic oligodendrocyte (OL) death and die before 2 years of age. However, the mechanisms of molecular pathogenesis in the developing OLs before death and the exact causes of white matter degeneration remain largely unknown. We have recently reported that OLs of twitcher mouse, an authentic mouse model of KD, exhibit developmental defects and endogenous accumulation of psychosine (galactosylsphingosine), a cytotoxic lyso-derivative of galactosylceramide. Here, we show that attenuated expression of microRNA (miR)-219, a critical regulator of OL differentiation and myelination, mediates cellular pathogenesis of KD OLs. Expression and functional activity of miR-219 were repressed in developing twitcher mouse OLs. By using OL precursor cells (OPCs) isolated from the twitcher mouse brain, we show that exogenously supplemented miR-219 effectively rescued their cell-autonomous developmental defects and apoptotic death. miR-219 also reduced endogenous accumulation of psychosine in twitcher OLs. Collectively, these results highlight the role of the reduced miR-219 expression in KD pathogenesis and suggest that miR-219 has therapeutic potential for treating KD OL pathologies.

Keywords:  Krabbe disease; demyelination; globoid cell leukodystrophy; lysosomal storage disease; microRNA; oligodendrocyte

DOI:  https://doi.org/10.1111/bpa.12951
Hum Mol Genet. 2021 Apr 05. pii: ddab093. [Epub ahead of print]

MCOLN1 gene therapy corrects neurologic dysfunction in the mouse model of mucolipidosis IV.

Samantha De Rosa, Monica Salani, Sierra Smith, Madison Sangster, Victoria Miller-Browne, Sarah Wassmer, Ru Xiao, Luk Vandenberghe, Susan Slaugenhaupt, Albert Misko, Yulia Grishchuk.

Mucolipidosis IV (MLIV) is an orphan disease leading to debilitating psychomotor deficits and vision loss. It is caused by loss-of-function mutations in the MCOLN1 gene that encodes the lysosomal transient receptor potential channel mucolipin1, or TRPML1. With no existing therapy, the unmet need in this disease is very high. Here we showed that AAV-mediated CNS-targeted gene transfer of the human MCOLN1 gene rescued motor function and alleviated brain pathology in the MLIV mouse model. Using the AAV-PHP.b vector in symptomatic mice, we showed long-term reversal of declined motor function and significant delay of paralysis. Next, using self-complementary AAV9 clinical candidate vector, we showed that its intracerebroventricular administration in post-natal day 1 mice significantly improved motor function, myelination and reduced lysosomal storage load in the MLIV mouse brain. Based on our data and general advancements in the gene therapy field, we propose scAAV9-mediated CSF-targeted MCOLN1 gene transfer as a therapeutic strategy in MLIV.

DOI: https://doi.org/10.1093/hmg/ddab093
Aging Pathobiol Ther. 2020 ;2(4): 187-194

Sex-dependent lifespan extension of Apc Min/+ FAP mice by chronic mTOR inhibition.

Manish Parihar, Sherry G Dodds, Marty Javors, Randy Strong, Paul Hasty, Zelton Dave Sharp.

   Background: ApcMin/+ mice model familial adenomatous polyposis (FAP), a disease that causes numerous colon polyps leading to colorectal cancer. We previously showed that chronic treatment of Apc Min/+ females with the anti-aging drug, rapamycin, restored a normal lifespan through reduced polyposis and anemia prevention. Lifespan extension by chronic rapamycin in wildtype UM-HET3 mice is sex-dependent with females gaining the most benefit. Whether Apc Min/+ mice have a similar sex-dependent response to chronic mTOR inhibition is not known.
Methods: To address this knowledge gap and gain deeper insight into how chronic mTOR inhibition prevents intestinal polyposis, we compared male and female Apc Min/+ mice responses to chronic treatment with a rapamycin-containing diet. Animals were fed a diet containing either 42 ppm microencapsulate rapamycin or empty capsules, one group was used to determine lifespan and a second group with similar treatment was harvested at 16 weeks of age for cross-sectional studies.
Results: We found that the survival of males is greater than females in this setting (P < 0.0197). To explore the potential basis for this difference we analyzed factors affected by chronic rapamycin. Immunoblot assays showed that males and females exhibited approximately the same level of mTORC1 inhibition using phosphorylation of ribosomal protein S6 (rpS6) as an indirect measure. Immunohistochemistry assays of rpS6 phosphorylation showed that rapamycin reduction of mTORC1 activity was on the same level, with the most prominent difference being in intestinal crypt Paneth cells in both sexes. Chronic rapamycin also reduced crypt depths in both male and female Apc Min/+ mice (P < 0.0001), consistent with reduced crypt epithelial cell proliferation. Finally, chronic rapamycin prevented anemia equally in males and females.
Conclusions: In males and females, these findings link rapamycin-mediated intestinal polyposis prevention with mTORC1 inhibition in Paneth cells and concomitant reduced epithelial cell proliferation.

Keywords:  Paneth cells; Rapamycin; crypt stem cells; mTORC1; polyposis; small intestine

DOI:  https://doi.org/10.31491/apt.2020.12.039
Sci Adv. 2021 Apr;pii: eabg4544. [Epub ahead of print]7(15):

AMPK/ULK1-mediated phosphorylation of Parkin ACT domain mediates an early step in mitophagy.

Chien-Min Hung, Portia S Lombardo, Nazma Malik, Sonja N Brun, Kristina Hellberg, Jeanine L Van Nostrand, Daniel Garcia, Joshua Baumgart, Ken Diffenderfer, John M Asara, Reuben J Shaw.

The serine/threonine kinase ULK1 mediates autophagy initiation in response to various cellular stresses, and genetic deletion of ULK1 leads to accumulation of damaged mitochondria. Here we identify Parkin, the core ubiquitin ligase in mitophagy, and PARK2 gene product mutated in familial Parkinson's disease, as a ULK1 substrate. Recent studies uncovered a nine residue ("ACT") domain important for Parkin activation, and we demonstrate that AMPK-dependent ULK1 rapidly phosphorylates conserved serine108 in the ACT domain in response to mitochondrial stress. Phosphorylation of Parkin Ser108 occurs maximally within five minutes of mitochondrial damage, unlike activation of PINK1 and TBK1, which is observed thirty to sixty minutes later. Mutation of the ULK1 phosphorylation sites in Parkin, genetic AMPK or ULK1 depletion, or pharmacologic ULK1 inhibition, all lead to delays in Parkin activation and defects in assays of Parkin function and downstream mitophagy events. These findings reveal an unexpected first step in the mitophagy cascade.

DOI: https://doi.org/10.1126/sciadv.abg4544
J Biol Chem. 2021 Apr 05. pii: S0021-9258(21)00422-1. [Epub ahead of print] 100636

PIKfyve activity is required for lysosomal trafficking of tau aggregates and tau seeding.

Alberto Carpinteiro Soares, Andreia Ferreira, Jonas Mariën, Charlotte Delay, Edward Lee, John Q Trojanowski, Dieder Moechars, Wim Annaert, Louis De Muynck.

  Tauopathies, such as Alzheimer's disease (AD), are neurodegenerative disorders characterized by the deposition of hyperphosphorylated tau aggregates. Proteopathic tau seeds spread through the brain in a temporospatial pattern, indicative of transsynaptic propagation. It is hypothesized that reducing the uptake of tau seeds and subsequent induction of tau aggregation could be a potential approach for abrogating disease progression in AD. Here, we studied to what extent different endosomal routes play a role in the neuronal uptake of pre-formed tau seeds. Using pharmacological and genetic tools we identified dynamin-1, actin and Rac1 as key players. Furthermore, inhibition of PIKfyve, a protein downstream of Rac1, reduced both the trafficking of tau seeds into lysosomes as well as the induction of tau aggregation. Our work shows that tau aggregates are internalized by a specific endocytic mechanism and that their fate once internalized can be pharmacologically modulated to reduce tau seeding in neurons.

Keywords:  Alzheimer’s disease; PIKfyve; Rac1; Tauopathy; tau seeding; tau uptake

DOI:  https://doi.org/10.1016/j.jbc.2021.100636
Dev Cell. 2021 Mar 31. pii: S1534-5807(21)00262-8. [Epub ahead of print]

Diverse nitrogen signals activate convergent ROP2-TOR signaling in Arabidopsis.

Yanlin Liu, Xiaoli Duan, Xiaodi Zhao, Wenlong Ding, Yaowei Wang, Yan Xiong.

  The evolutionarily conserved target-of-rapamycin (TOR) kinase coordinates cellular and organismal growth in all eukaryotes. Amino acids (AAs) are key upstream signals for mammalian TOR activation, but how nitrogen-related nutrients regulate TOR signaling in plants is poorly understood. Here, we discovered that, independent of nitrogen assimilation, nitrate and ammonium function as primary nitrogen signals to activate TOR in the Arabidopsis leaf primordium. We further identified that a total of 15 proteinogenic AAs are also able to activate TOR, and the first AAs generated from plant specific nitrogen assimilation (glutamine), sulfur assimilation (cysteine), and glycolate cycle (glycine), exhibit the highest potency. Interestingly, nitrate, ammonium, and glutamine all activate the small GTPase Rho-related protein from plants 2 (ROP2), and constitutively active ROP2 restores TOR activation under nitrogen-starvation conditions. Our findings suggest that specific evolutionary adaptations of the nitrogen-TOR signaling pathway occurred in plant lineages, and ROP2 can integrate diverse nitrogen and hormone signals for plant TOR activation.

Keywords:  ROP2; TOR; amino acids; cell proliferation; inorganic nitrogen; leaf primordium

DOI:  https://doi.org/10.1016/j.devcel.2021.03.022
Front Cell Infect Microbiol. 2021 ;11 633360

Regulatory Mechanisms of Autophagy-Targeted Antimicrobial Therapeutics Against Mycobacterial Infection.

Prashanta Silwal, Seungwha Paik, Jin Kyung Kim, Tamotsu Yoshimori, Eun-Kyeong Jo.

  Mycobacterium tuberculosis (Mtb) is an intracellular pathogen causing human tuberculosis, an infectious disease that still remains as a global health problem. Autophagy, a lysosomal degradative process, has emerged as a critical pathway to restrict intracellular Mtb growth through enhancement of phagosomal maturation. Indeed, several autophagy-modulating agents show promise as host-directed therapeutics for Mtb infection. In this Review, we discuss recent progress in our understanding the molecular mechanisms underlying the action of autophagy-modulating agents to overcome the immune escape strategies mediated by Mtb. The factors and pathways that govern such mechanisms include adenosine 5'-monophosphate-activated protein kinase, Akt/mammalian TOR kinase, Wnt signaling, transcription factor EB, cathelicidins, inflammation, endoplasmic reticulum stress, and autophagy-related genes. A further understanding of these mechanisms will facilitate the development of host-directed therapies against tuberculosis as well as infections with other intracellular bacteria targeted by autophagic degradation.

Keywords:  AMPK; Mycobacterium tuberculosis; autophagy; host-directed therapeutics; mTOR

DOI:  https://doi.org/10.3389/fcimb.2021.633360
J Membr Biol. 2021 Apr 07.

Unveiling the Dynamics of KRAS4b on Lipid Model Membranes.

Cesar A López, Animesh Agarwal, Que N Van, Andrew G Stephen, S Gnanakaran.

  Small GTPase proteins are ubiquitous and responsible for regulating several processes related to cell growth and differentiation. Mutations that stabilize their active state can lead to uncontrolled cell proliferation and cancer. Although these proteins are well characterized at the cellular scale, the molecular mechanisms governing their functions are still poorly understood. In addition, there is limited information about the regulatory function of the cell membrane which supports their activity. Thus, we have studied the dynamics and conformations of the farnesylated KRAS4b in various membrane model systems, ranging from binary fluid mixtures to heterogeneous raft mimics. Our approach combines long time-scale coarse-grained (CG) simulations and Markov state models to dissect the membrane-supported dynamics of KRAS4b. Our simulations reveal that protein dynamics is mainly modulated by the presence of anionic lipids and to some extent by the nucleotide state (activation) of the protein. In addition, our results suggest that both the farnesyl and the polybasic hypervariable region (HVR) are responsible for its preferential partitioning within the liquid-disordered (Ld) domains in membranes, potentially enhancing the formation of membrane-driven signaling platforms.

Keywords:  Cancer; KRAS4b; Molecular dynamics

DOI:  https://doi.org/10.1007/s00232-021-00176-z
Biochemistry (Mosc). 2021 Feb;86(2): 146-155

The Mechanisms of L-Arginine Metabolism Disorder in Endothelial Cells.

Jennet T Mammedova, Alexey V Sokolov, Irina S Freidlin, Eleonora A Starikova.

  L-arginine is a key metabolite for nitric oxide production by endothelial cells, as well as signaling molecule of the mTOR signaling pathway. mTOR supports endothelial cells homeostasis and regulates activity of L-arginine-metabolizing enzymes, endothelial nitric oxide synthase, and arginase II. Disruption of the L-arginine metabolism in endothelial cells leads to the development of endothelial dysfunction. Conflicting results of the use of L-arginine supplement to improve endothelial function reveals a controversial role of the amino acid in the endothelial cell biology. The review is aimed at analysis of the current data on the role of L-arginine metabolism in the development of endothelial dysfunction.

Keywords:  L-arginine; arginase; eNOS; endothelium; mTOR; nitric oxide

DOI:  https://doi.org/10.1134/S0006297921020036
Life Sci. 2021 Apr 05. pii: S0024-3205(21)00447-1. [Epub ahead of print] 119462

Over-expressed RHEB promotes the progression of pancreatic adenocarcinoma.

Juan Tan, Waner Liu, Jie Li, Xi Zhang, Yang Liu, Yuan Yuan, Zewen Song.

   AIMS: Mammalian/mechanistic target of rapamycin (mTOR) is essential in the progression of pancreatic adenocarcinoma (PAAD). But the role of Ras homolog enriched in brain (RHEB), a key activator of mTORC1, is unclear in this disease. This work aims to clarify the function of RHEB in PAAD.
MATERIALS AND METHODS: A pan-cancer analysis of RHEB was conducted by using data from several public available databases. Immunohistochemical (IHC) staining on a tissue microarray was used to validate the expression of RHEB in PAAD. In vitro experiments were conducted to explore the function of RHEB in the disease. An integrated bioinformatics tools were used to understand the mechanism of RHEB and construct a RHEB-related prognostic signature.
KEY FINDINGS: RHEB was significantly overexpressed in PAAD and high expression of the gene was associated with poor prognosis. RHEB promoted proliferation, migration and invasion of pancreatic cancer cells. Gene set enrichment analysis (GSEA) showed that RHEB participated in cell cycle progression and WNT signaling pathway. A RHEB-related prognostic signature was developed, and PAAD patients with high risk score had a significantly shorter overall survival.
SIGNIFICANCE: RHEB was up-regulated in PAAD and might be a useful therapeutic target.

Keywords:  Cell proliferation; Pancreatic cancer; Prognostic signature; RHEB; mTOR

DOI:  https://doi.org/10.1016/j.lfs.2021.119462
Biophys Chem. 2020 Dec 25. pii: S0301-4622(20)30242-8. [Epub ahead of print] 106534

The interplay between Glucocerebrosidase, α-synuclein and lipids in human models of Parkinson's disease.

Sonia Sanz Muñoz, Daniel Petersen, Frederik Ravnkilde Marlet, Ebru Kücükköse, Céline Galvagnion.

  Mutations in the gene GBA, encoding glucocerebrosidase (GCase), are the highest genetic risk factor for Parkinson's disease (PD). GCase is a lysosomal glycoprotein responsible for the hydrolysis of glucosylceramide into glucose and ceramide. Mutations in GBA cause a decrease in GCase activity, stability and protein levels which in turn lead to the accumulation of GCase lipid substrates as well as α-synuclein (αS) in vitro and in vivo. αS is the main constituent of Lewy bodies found in the brain of PD patients and an increase in its levels was found to be associated with a decrease in GCase activity/protein levels in vitro and in vivo. In this review, we describe the reported biophysical and biochemical changes that GBA mutations can induce in GCase activity and stability as well as the current overview of the levels of GCase protein/activity, αS and lipids measured in patient-derived samples including post-mortem brains, stem cell-derived neurons, cerebrospinal fluid, blood and fibroblasts as well as in SH-SY5Y cells. In particular, we report how the levels of αS and lipids are affected by/correlated to significant changes in GCase activity/protein levels and which cellular pathways are activated or disrupted by these changes in each model. Finally, we review the current strategies used to revert the changes in the levels of GCase activity/protein, αS and lipids in the context of PD.

Keywords:  Amyloid; Glucocerebrosidase; Human models; Lipids; Parkinson’s disease; α-synuclein

DOI:  https://doi.org/10.1016/j.bpc.2020.106534
Proc Natl Acad Sci U S A. 2021 Mar 16. pii: e2016276118. [Epub ahead of print]118(11):

A unique C2 domain at the C terminus of Munc13 promotes synaptic vesicle priming.

Murugesh Padmanarayana, Haowen Liu, Francesco Michelassi, Lei Li, Daniel Betensky, Matthew J Dominguez, R Bryan Sutton, Zhitao Hu, Jeremy S Dittman.

  Neurotransmitter release during synaptic transmission comprises a tightly orchestrated sequence of molecular events, and Munc13-1 is a cornerstone of the fusion machinery. A forward genetic screen for defects in neurotransmitter release in Caenorhabditis elegans identified a mutation in the Munc13-1 ortholog UNC-13 that eliminated its unique and deeply conserved C-terminal module (referred to as HC2M) containing a Ca2+-insensitive C2 domain flanked by membrane-binding helices. The HC2M module could be functionally replaced in vivo by protein domains that localize to synaptic vesicles but not to the plasma membrane. HC2M is broadly conserved in other Unc13 family members and is required for efficient synaptic vesicle priming. We propose that the HC2M domain evolved as a vesicle/endosome adaptor and acquired synaptic vesicle specificity in the Unc13ABC protein family.

Keywords:  C2; Caenorhabditis elegans; Munc13; synaptic vesicle; unc-13

DOI:  https://doi.org/10.1073/pnas.2016276118
Enzymes. 2020 ;pii: S1874-6047(20)30002-0. [Epub ahead of print]48 243-275

Aminoacyl-tRNA synthetases in cell signaling.

Peng Yao, Paul L Fox.

  Aminoacyl-tRNA synthetases (ARSs) are a family of essential "housekeeping" enzymes ubiquitous in the three major domains of life. ARSs uniquely connect the essential minimal units of both major oligomer classes-the 3-nucleotide codons of oligonucleotides and the amino acids of proteins. They catalyze the esterification of amino acids to the 3'-end of cognate transfer RNAs (tRNAs) bearing the correct anticodon triplet to ensure accurate transfer of information from mRNA to protein according to the genetic code. As an essential translation factor responsible for the first biochemical reaction in protein biosynthesis, ARSs control protein production by catalyzing aminoacylation, and by editing of mischarged aminoacyl-tRNAs to maintain translational fidelity. In addition to their primary enzymatic activities, many ARSs have noncanonical functions unrelated to their catalytic activity in protein synthesis. Among the ARSs with "moonlighting" activities, several, including GluProRS (or EPRS), LeuRS, LysRS, SerRS, TyrRS, and TrpRS, exhibit cell signaling-related activities that sense environmental signals, regulate gene expression, and modulate cellular functions. ARS signaling functions generally depend on catalytically-inactive, appended domains not present in ancient enzyme forms, and are activated by stimulus-dependent post-translational modification. Activation often results in cellular re-localization and gain of new interacting partners. The newly formed ARS-bearing complexes conduct a host of signal transduction functions, including immune response, mTORC1 pathway signaling, and fibrogenic and angiogenic signaling, among others. Because noncanonical functions of ARSs in signal transduction are uncoupled from canonical aminoacylation functions, function-specific inhibitors can be developed, thus providing promising opportunities and therapeutic targets for treatment of human disease.

Keywords:  Aminoacyl-tRNA synthetase; Antiviral response; Cell signaling; Fibrosis; GluProRS; LeuRS; LysRS; Metabolism; Noncanonical function; mTORC1

DOI:  https://doi.org/10.1016/bs.enz.2020.04.002
Nature. 2021 Apr 07.

Cell-programmed nutrient partitioning in the tumour microenvironment.

Bradley I Reinfeld, Matthew Z Madden, Melissa M Wolf, Anna Chytil, Jackie E Bader, Andrew R Patterson, Ayaka Sugiura, Allison S Cohen, Ahmed Ali, Brian T Do, Alexander Muir, Caroline A Lewis, Rachel A Hongo, Kirsten L Young, Rachel E Brown, Vera M Todd, Tessa Huffstater, Abin Abraham, Richard T O'Neil, Matthew H Wilson, Fuxue Xin, M Noor Tantawy, W David Merryman, Rachelle W Johnson, Christopher S Williams, Emily F Mason, Frank M Mason, Katherine E Beckermann, Matthew G Vander Heiden, H Charles Manning, Jeffrey C Rathmell, W Kimryn Rathmell.

Cancer cells characteristically consume glucose through Warburg metabolism1, a process that forms the basis of tumour imaging by positron emission tomography (PET). Tumour-infiltrating immune cells also rely on glucose, and impaired immune cell metabolism in the tumour microenvironment (TME) contributes to immune evasion by tumour cells2-4. However, whether the metabolism of immune cells is dysregulated in the TME by cell-intrinsic programs or by competition with cancer cells for limited nutrients remains unclear. Here we used PET tracers to measure the access to and uptake of glucose and glutamine by specific cell subsets in the TME. Notably, myeloid cells had the greatest capacity to take up intratumoral glucose, followed by T cells and cancer cells, across a range of cancer models. By contrast, cancer cells showed the highest uptake of glutamine. This distinct nutrient partitioning was programmed in a cell-intrinsic manner through mTORC1 signalling and the expression of genes related to the metabolism of glucose and glutamine. Inhibiting glutamine uptake enhanced glucose uptake across tumour-resident cell types, showing that glutamine metabolism suppresses glucose uptake without glucose being a limiting factor in the TME. Thus, cell-intrinsic programs drive the preferential acquisition of glucose and glutamine by immune and cancer cells, respectively. Cell-selective partitioning of these nutrients could be exploited to develop therapies and imaging strategies to enhance or monitor the metabolic programs and activities of specific cell populations in the TME.

DOI: https://doi.org/10.1038/s41586-021-03442-1
J Photochem Photobiol B. 2021 Mar 29. pii: S1011-1344(21)00061-0. [Epub ahead of print]218 112183

Lysosome-targeted photodynamic treatment induces primary keratinocyte differentiation.

Neringa Daugelaviciene, Pranas Grigaitis, Liepa Gasiule, Daiva Dabkeviciene, Urte Neniskyte, Ausra Sasnauskiene.

  Photodynamic therapy is an attractive technique for various skin tumors and non-cancerous skin lesions. However, while the aim of photodynamic therapy is to target and damage only the malignant cells, it unavoidably affects some of the healthy cells surrounding the tumor as well. However, data on the effects of PDT to normal cells are scarce, and the characterization of the pathways activated after the photodamage of normal cells may help to improve clinical photodynamic therapy. In our study, primary human epidermal keratinocytes were used to evaluate photodynamic treatment effects of photosensitizers with different subcellular localization. We compared the response of keratinocytes to lysosomal photodamage induced by phthalocyanines, aluminum phthalocyanine disulfonate (AlPcS2a) or aluminum phthalocyanine tetrasulfonate (AlPcS4), and cellular membrane photodamage by m-tetra(3-hydroxyphenyl)-chlorin (mTHPC). Our data showed that mTHPC-PDT promoted autophagic flux, whereas lysosomal photodamage induced by aluminum phthalocyanines evoked differentiation and apoptosis. Photodamage by AlPcS2a, which is targeted to lysosomal membranes, induced keratinocyte differentiation and apoptosis more efficiently than AlPcS4, which is targeted to lysosomal lumen. Computational analysis of the interplay between these molecular pathways revealed that keratin 10 is the coordinating molecular hub of primary keratinocyte differentiation, apoptosis and autophagy.

Keywords:  AlPcS(2a); AlPcS(4); Keratin 10; Keratinocyte differentiation; Lysosome; Photodynamic treatment; Primary human epidermal keratinocytes; mTHPC

DOI:  https://doi.org/10.1016/j.jphotobiol.2021.112183
Front Endocrinol (Lausanne). 2021 ;12 627745

Signaling Pathways Involved in Nutrient Sensing Control in Cancer Stem Cells: An Overview.

Martha Robles-Flores, Angela P Moreno-Londoño, M Cristina Castañeda-Patlán.

  Cancer cells characteristically have a high proliferation rate. Because tumor growth depends on energy-consuming anabolic processes, including biosynthesis of protein, lipid, and nucleotides, many tumor-associated conditions, including intermittent oxygen deficiency due to insufficient vascularization, oxidative stress, and nutrient deprivation, results from fast growth. To cope with these environmental stressors, cancer cells, including cancer stem cells, must adapt their metabolism to maintain cellular homeostasis. It is well- known that cancer stem cells (CSC) reprogram their metabolism to adapt to live in hypoxic niches. They usually change from oxidative phosphorylation to increased aerobic glycolysis even in the presence of oxygen. However, as opposed to most differentiated cancer cells relying on glycolysis, CSCs can be highly glycolytic or oxidative phosphorylation-dependent, displaying high metabolic plasticity. Although the influence of the metabolic and nutrient-sensing pathways on the maintenance of stemness has been recognized, the molecular mechanisms that link these pathways to stemness are not well known. Here in this review, we describe the most relevant signaling pathways involved in nutrient sensing and cancer cell survival. Among them, Adenosine monophosphate (AMP)-activated protein kinase (AMPK) pathway, mTOR pathway, and Hexosamine Biosynthetic Pathway (HBP) are critical sensors of cellular energy and nutrient status in cancer cells and interact in complex and dynamic ways.

Keywords:  adenosine monophosphate-activated protein kinase (AMPK) signaling; cancer stem cells; hexosamine biosynthesis pathway (HBP) pathway; mammalian target of rapamycin (mTOR) signaling; nutrient sensing

DOI:  https://doi.org/10.3389/fendo.2021.627745
J Cell Biol. 2021 May 03. pii: e202006040. [Epub ahead of print]220(5):

Rab2 regulates presynaptic precursor vesicle biogenesis at the trans-Golgi.

Torsten W B Götz, Dmytro Puchkov, Veronika Lysiuk, Janine Lützkendorf, Alexander G Nikonenko, Christine Quentin, Martin Lehmann, Stephan J Sigrist, Astrid G Petzoldt.

Reliable delivery of presynaptic material, including active zone and synaptic vesicle proteins from neuronal somata to synaptic terminals, is prerequisite for successful synaptogenesis and neurotransmission. However, molecular mechanisms controlling the somatic assembly of presynaptic precursors remain insufficiently understood. We show here that in mutants of the small GTPase Rab2, both active zone and synaptic vesicle proteins accumulated in the neuronal cell body at the trans-Golgi and were, consequently, depleted at synaptic terminals, provoking neurotransmission deficits. Ectopic presynaptic material accumulations consisted of heterogeneous vesicles and short tubules of 40 × 60 nm, segregating in subfractions either positive for active zone or synaptic vesicle proteins and LAMP1, a lysosomal membrane protein. Genetically, Rab2 acts upstream of Arl8, a lysosomal adaptor controlling axonal export of precursors. Collectively, we identified a Golgi-associated assembly sequence of presynaptic precursor biogenesis dependent on a Rab2-regulated protein export and sorting step at the trans-Golgi.

DOI: https://doi.org/10.1083/jcb.202006040
Nat Rev Mol Cell Biol. 2021 Apr 09.

Intracellular mRNA transport and localized translation.

Sulagna Das, Maria Vera, Valentina Gandin, Robert H Singer, Evelina Tutucci.

Fine-tuning cellular physiology in response to intracellular and environmental cues requires precise temporal and spatial control of gene expression. High-resolution imaging technologies to detect mRNAs and their translation state have revealed that all living organisms localize mRNAs in subcellular compartments and create translation hotspots, enabling cells to tune gene expression locally. Therefore, mRNA localization is a conserved and integral part of gene expression regulation from prokaryotic to eukaryotic cells. In this Review, we discuss the mechanisms of mRNA transport and local mRNA translation across the kingdoms of life and at organellar, subcellular and multicellular resolution. We also discuss the properties of messenger ribonucleoprotein and higher order RNA granules and how they may influence mRNA transport and local protein synthesis. Finally, we summarize the technological developments that allow us to study mRNA localization and local translation through the simultaneous detection of mRNAs and proteins in single cells, mRNA and nascent protein single-molecule imaging, and bulk RNA and protein detection methods.

DOI: https://doi.org/10.1038/s41580-021-00356-8
Dev Cell. 2021 Apr 05. pii: S1534-5807(21)00209-4. [Epub ahead of print]56(7): 878-880

Organelle homeostasis principles: How organelle quality control and inter-organelle crosstalk promote cell survival.

W Mike Henne.

To survive, cells sense their surroundings and adapt to enable homeostasis. Studies dissecting this process reveal organizational principles, including quality-control pathways, changes to organelle shape, and inter-organelle communication, that facilitate metabolic or developmental remodeling. In this issue, several reviews discuss these organelle homeostasis principles and how they are altered in disease.

DOI: https://doi.org/10.1016/j.devcel.2021.03.012
Mol Cancer. 2021 Apr 04. 20(1): 61

The m6A RNA methylation regulates oncogenic signaling pathways driving cell malignant transformation and carcinogenesis.

Mohammad Burhan Uddin, Zhishan Wang, Chengfeng Yang.

  The m6A RNA methylation is the most prevalent internal modification in mammalian mRNAs which plays critical biological roles by regulating vital cellular processes. Dysregulations of the m6A modification due to aberrant expression of its regulatory proteins are frequently observed in many pathological conditions, particularly in cancer. Normal cells undergo malignant transformation via activation or modulation of different oncogenic signaling pathways through complex mechanisms. Accumulating evidence showing regulation of oncogenic signaling pathways at the epitranscriptomic level has added an extra layer of the complexity. In particular, recent studies demonstrated that, in many types of cancers various oncogenic signaling pathways are modulated by the m6A modification in the target mRNAs as well as noncoding RNA transcripts. m6A modifications in these RNA molecules control their fate and metabolism by regulating their stability, translation or subcellular localizations. In this review we discussed recent exciting studies on oncogenic signaling pathways that are modulated by the m6A RNA modification and/or their regulators in cancer and provided perspectives for further studies. The regulation of oncogenic signaling pathways by the m6A modification and its regulators also render them as potential druggable targets for the treatment of cancer.

Keywords:  Carcinogenesis; Cell transformation; Epitranscriptomics; Signal transduction; m6A

DOI:  https://doi.org/10.1186/s12943-021-01356-0
Sci Rep. 2021 Apr 08. 11(1): 7787

Oncogenic role of MiR-130a in oral squamous cell carcinoma.

Karthik Mallela, Swamy Shivananda, Kodaganur S Gopinath, Arun Kumar.

Aberrant activation of the PI3K/AKT/mTOR pathway is attributed to the pathogenesis of oral squamous cell carcinoma (OSCC). In recent years, increasing evidence suggests the involvement of microRNAs (miRNAs) in oral carcinogenesis by acting as tumor suppressors or oncogenes. TSC1, as a component of the above pathway, regulates several cellular functions such as cell proliferation, apoptosis, migration and invasion. Downregulation of TSC1 is reported in oral as well as several other cancers and is associated with an unfavourable clinical outcome in patients. Here we show that oncogenic miR-130a binds to the 3'UTR of TSC1 and represses its expression. MiR-130a-mediated repression of TSC1 increases cell proliferation, anchorage independent growth and invasion of OSCC cells, which is dependent on the presence of the 3'UTR in TSC1. We observe an inverse correlation between the expression levels of miR-130a and TSC1 in OSCC samples, suggesting that their interaction is physiologically relevant. Delivery of antagomiR-130a to OSCC cells results in a significant decrease in xenograft size. Taken together, the findings of the study indicate that miR-130a-mediated TSC1 downregulation is not only a novel mechanism in OSCC, but also the restoration of TSC1 levels by antagomiR-130a may be a potential therapeutic strategy for the treatment of OSCC.

DOI: https://doi.org/10.1038/s41598-021-87388-4