bims-lypmec 2022-12-04 papers

bims-lypmec

Biomed News

on Lysosomal positioning and metabolism in cardiomyocytes

Issue of 2022–12–04
eight papers selected by
Satoru Kobayashi, New York Institute of Technology

Altered Lysosomal Function Manipulates Cellular Biosynthetic Capacity By Remodeling Intracellular Cholesterol Distribution.
RAB7A GTPase Is Involved in Mitophagosome Formation and Autophagosome-Lysosome Fusion in N2a Cells Treated with the Prion Protein Fragment 106-126.
Acidic pH-Triggered Live-Cell Lysosome Specific Tracking, Ratiometric pH Sensing, and Multicolor Imaging by Visible to NIR Switchable Cy-7 Dyes.
Protein mishandling and impaired lysosomal proteolysis generated through calcium dysregulation in Alzheimer's disease.
TFEB acetylation promotes lysosome biogenesis and ameliorates Alzheimer's disease-relevant phenotypes in mice.
Lysosomal damage drives mitochondrial proteome remodelling and reprograms macrophage immunometabolism.
The lysosomal Ragulator complex activates NLRP3 inflammasome in vivo via HDAC6.
G3BP1 coordinates lysophagy activity to protect against compression-induced cell ferroptosis during intervertebral disc degeneration.

Cell Biochem Biophys. 2022 Dec 02.

Altered Lysosomal Function Manipulates Cellular Biosynthetic Capacity By Remodeling Intracellular Cholesterol Distribution.

Sudarshana Rajasekaran, Anand Ramaian Santhaseela, Shamila Ragunathan, Sangita Venkataraman, Tamilselvan Jayavelu.

  Lysosomes are known to influence cholesterol trafficking into endoplasmic reticulum (ER) membranes. Though intracellular cholesterol levels are known to influence the lipid biosynthetic responses in ER, the specific effects of lysosomal modulation on these outcomes is not known. To demonstrate this, C2C12 cells were treated with chloroquine, a lysosomotropic agent, and its effects on cellular biosynthetic capacity, structural and functional status of ER was determined. In addition to its known effects on autophagy reduction, chloroquine treatment induced accumulation of total cellular lipid and ER-specific cholesterol content. It was also observed that chloroquine caused an increase in smooth-ER content with defects in overall protein turnover. Further, since ER and mitochondria function in close association through ER membrane contact sites, it is likely that lysosomal modulation also brings about associated changes in mitochondria. In this regard, we found that chloroquine reduces mitochondrial membrane potential and mitochondrial dynamics. Collectively, the differential biosynthetic response of rise in lipid content, but not protein content, cannot be accounted by merely considering that chloroquine induced suppression of autophagy causes defects in organelle function. In this defective autophagy scenario, both biosynthetic responses such as lipid and protein synthesis are expected to be reduced rather than only the latter, as observed with chloroquine. These findings suggest that cholesterol trafficking/distribution within cellular organelles could act as an intracellular mediator of differential biosynthetic remodelling in interconnected organelles.

Keywords:  Chloroquine; Cholesterol; Endoplasmic reticulum; Lysosome; Mitochondria

DOI:  https://doi.org/10.1007/s12013-022-01123-y
Mol Neurobiol. 2022 Nov 30.

RAB7A GTPase Is Involved in Mitophagosome Formation and Autophagosome-Lysosome Fusion in N2a Cells Treated with the Prion Protein Fragment 106-126.

Zhiping Li, Mengyu Lai, Jie Li, Dongming Yang, Mengyang Zhao, Dongdong Wang, Zhixin Sun, Pei Wen, Fengting Gou, Yuexin Dai, Yilan Ji, Deming Zhao, Jian Qiao, Lifeng Yang.

  Failed communication between mitochondria and lysosomes causes dysfunctional mitochondria, which may induce mitochondria-related neurodegenerative diseases. Here, we show that RAB7A, a small GTPase of the Rab family, mediates the crosstalk between these two important organelles to maintain homeostasis in N2a cells treated with PrP106-126. Specifically, we demonstrate that mitophagy deficiency in N2a cells caused by PrP106-126 is associated with dysregulated RAB7A localization in mitochondria. Cells lacking RAB7A display decreased mitochondrial colocalization with lysosomes and significantly increased mitochondrial protein expression, resulting in inhibited mitophagy. In contrast, overexpression of GTP-bound RAB7A directly induces lysosome colocalization with mitochondria. Further study revealed that GTP-bound RAB7A protects mitochondrial homeostasis by supporting autophagosome biogenesis. Moreover, we suggest that depletion of RAB7A leads to gross morphological changes in lysosomes, which prevents autophagosome-lysosome fusion and interferes with the breakdown of autophagic cargo within lysosomes. Overexpression of GTP-bound RAB7A can also alleviate PrP106-126-induced morphological damage and dysfunction of mitochondria, reducing neuronal apoptosis. Collectively, our data demonstrate that RAB7A successfully drives mitochondria to the autophagosomal lumen for degradation, suggesting that the communication of proteotoxic stress from mitochondria to lysosomes requires RAB7A, as a signaling molecule, to establish a link between the disturbed mitochondrial network and its remodeling. These findings indicate that small molecules regulating mitophagy have the potential to modulate cellular homeostasis and the clinical course of neurodegenerative diseases. Proposed model of mitophagy regulated by RAB7A. (1) Accumulating PrP106-126 induced mitophagy. (2) RAB7A is recruited to mitochondria. (3) ATG5-12 and ATG9A (5) vesicles are recruited to the autophagosome formation sites in a RAB7A-dependent manner. The ATG5-12 complex recruits and anchors LC3-I to form active LC3-II (4), accelerating mitophagosomal formation. The ATG9A vesicles are thought to be a source of membranes for autophagosome assembly. The recruitment of proteins and lipids induces membrane expansion and subsequent closure to form the mitophagosome. (6) Maintenance of the normal low lysosomal PH depends on active (GTP-bound) RAB7A. (7) RAB7A recruits effector molecules responsible for tight membrane interactions, and directly or indirectly, the subsequent autophagosome merges with the lysosome, and the cargo is completely degraded.

Keywords:  Mitochondria; Mitophagy; N2a; Neurodegenerative diseases; PrP106–126; RAB7A

DOI:  https://doi.org/10.1007/s12035-022-03118-5
Chembiochem. 2022 Dec 02.

Acidic pH-Triggered Live-Cell Lysosome Specific Tracking, Ratiometric pH Sensing, and Multicolor Imaging by Visible to NIR Switchable Cy-7 Dyes.

Ayan Mukherjee, Pranab Chandra Saha, Samiran Kar, Pampa Guha, Rabi Sankar Das, Tapas Bera, Samit Guha.

  We have demonstrated an efficient synthetic route with crystal structures for the construction of acidic pH-triggered visible to NIR interchangeable ratiometric fluorescent pH sensors. This bioresponsive probe exhibits pH-sensitive reversible absorption/emission features, low cytotoxicity, 322 nm huge bathochromic spectral shift with augmented quantum yield from neutral to acidic pH, high sensitivity and selective targeting ability of live cell lysosomes with ideal pKa, off-to-on narrow NIR absorption/fluorescence signals with high molar absorption coefficient at acidic lysosomal lumen, and in situ live cell pH-activated ratiometric imaging of lysosomal pH. Selective staining and ratiometric pH imaging in human carcinoma live cell lysosomes is monitored by dual channel confocal laser scanning microscope using the pH-activatable organic fluorescent dye comprising a morpholine moiety for lysosome targeting and an acidic pH openable oxazolidine ring. Moreover, real-time tracking of lysosomes, 3D, and multicolor live cell imaging have been achieved using the synthesized pH-activatable probe.

Keywords:  activatable Cy-7 dye* live cell lysosomal imaging* molecular switching* multicolor imaging* ratiometric sensing

DOI:  https://doi.org/10.1002/cbic.202200641
Proc Natl Acad Sci U S A. 2022 Dec 06. 119(49): e2211999119

Protein mishandling and impaired lysosomal proteolysis generated through calcium dysregulation in Alzheimer's disease.

Sarah Mustaly-Kalimi, Wacey Gallegos, Robert A Marr, Alice Gilman-Sachs, Daniel A Peterson, Israel Sekler, Grace E Stutzmann.

  Impairments in neural lysosomal- and autophagic-mediated degradation of cellular debris contribute to neuritic dystrophy and synaptic loss. While these are well-characterized features of neurodegenerative disorders such as Alzheimer's disease (AD), the upstream cellular processes driving deficits in pathogenic protein mishandling are less understood. Using a series of fluorescent biosensors and optical imaging in model cells, AD mouse models and human neurons derived from AD patients, we reveal a previously undescribed cellular signaling cascade underlying protein mishandling mediated by intracellular calcium dysregulation, an early component of AD pathogenesis. Increased Ca2+ release via the endoplasmic reticulum (ER)-resident ryanodine receptor (RyR) is associated with reduced expression of the lysosome proton pump vacuolar-ATPase (vATPase) subunits (V1B2 and V0a1), resulting in lysosome deacidification and disrupted proteolytic activity in AD mouse models and human-induced neurons (HiN). As a result of impaired lysosome digestive capacity, mature autophagosomes with hyperphosphorylated tau accumulated in AD murine neurons and AD HiN, exacerbating proteinopathy. Normalizing AD-associated aberrant RyR-Ca2+ signaling with the negative allosteric modulator, dantrolene (Ryanodex), restored vATPase levels, lysosomal acidification and proteolytic activity, and autophagic clearance of intracellular protein aggregates in AD neurons. These results highlight that prior to overt AD histopathology or cognitive deficits, aberrant upstream Ca2+ signaling disrupts lysosomal acidification and contributes to pathological accumulation of intracellular protein aggregates. Importantly, this is demonstrated in animal models of AD, and in human iPSC-derived neurons from AD patients. Furthermore, pharmacological suppression of RyR-Ca2+ release rescued proteolytic function, revealing a target for therapeutic intervention that has demonstrated effects in clinically-relevant assays.

Keywords:  Alzheimer's disease; calcium; lysosome; ryanodine receptor; vATPase

DOI:  https://doi.org/10.1073/pnas.2211999119
J Biol Chem. 2022 Oct 27. pii: S0021-9258(22)01092-4. [Epub ahead of print]298(12): 102649

TFEB acetylation promotes lysosome biogenesis and ameliorates Alzheimer's disease-relevant phenotypes in mice.

Tianyou Li, Limin Yin, Xinyi Kang, Wenlong Xue, Ning Wang, Jie Zhang, Ping Yuan, Lingxi Lin, Yang Li.

  Lysosomes are one of the major centers for regulating cargo degradation and protein quality control. Transcription factor EB (TFEB)-promoted lysosome biogenesis enhances lysosome-mediated degradation and alleviates neurodegenerative diseases, but the mechanisms underlying TFEB modification and activation are still poorly understood. Here, we report essential roles of TFEB acetylation in TFEB nuclear translocation and lysosome biogenesis, which are independent of TFEB dephosphorylation. By screening small molecules, we find that Trichostatin A (TSA), the pan-inhibitor of histone deacetylases (HDACs), promotes nuclear translocation of TFEB. TSA enhances the staining of cells by LysoTracker Red and increases the expression of lysosomal and autophagic genes. We identify four novel acetylated lysine residues in TFEB, which are important for TFEB nuclear translocation and lysosome biogenesis. We show that TFEB acetylation is regulated by HDACs (HDAC5, HDAC6, and HDAC9) and lysine acetyltransferases (KATs), including ELP3, CREBBP, and HAT1. During TSA-induced cytosol-to-nucleus translocation of TFEB, acetylation is independent of TFEB dephosphorylation, since the mTORC1- or GSK3β-related phosphorylation sites on TFEB are still phosphorylated. Administration of TSA to APP/PS1 mice increases the expression of lysosomal and autophagic genes in mouse brains and also improves memory. Accordingly, the β-amyloid plaque burden is decreased. These results show that the acetylation of TFEB, as a novel mechanism of TFEB activation, promotes lysosome biogenesis and alleviates the pathogenesis of Alzheimer's disease. Our results also suggest that HDAC inhibition can promote lysosome biogenesis, and this may be a potential therapeutic approach for the treatment of neurodegenerative diseases and disorders related to HDAC hyperactivation.

Keywords:  Alzheimer’s disease; TFEB; acetylation; dephosphorylation; lysosome biogenesis; ubiquitination

DOI:  https://doi.org/10.1016/j.jbc.2022.102649
Nat Commun. 2022 Nov 28. 13(1): 7338

Lysosomal damage drives mitochondrial proteome remodelling and reprograms macrophage immunometabolism.

Claudio Bussi, Tiaan Heunis, Enrica Pellegrino, Elliott M Bernard, Nourdine Bah, Mariana Silva Dos Santos, Pierre Santucci, Beren Aylan, Angela Rodgers, Antony Fearns, Julia Mitschke, Christopher Moore, James I MacRae, Maria Greco, Thomas Reinheckel, Matthias Trost, Maximiliano G Gutierrez.

Transient lysosomal damage after infection with cytosolic pathogens or silica crystals uptake results in protease leakage. Whether limited leakage of lysosomal contents into the cytosol affects the function of cytoplasmic organelles is unknown. Here, we show that sterile and non-sterile lysosomal damage triggers a cell death independent proteolytic remodelling of the mitochondrial proteome in macrophages. Mitochondrial metabolic reprogramming required leakage of lysosomal cathepsins and was independent of mitophagy, mitoproteases and proteasome degradation. In an in vivo mouse model of endomembrane damage, live lung macrophages that internalised crystals displayed impaired mitochondrial function. Single-cell RNA-sequencing revealed that lysosomal damage skewed metabolic and immune responses in alveolar macrophages subsets with increased lysosomal content. Functionally, drug modulation of macrophage metabolism impacted host responses to Mycobacterium tuberculosis infection in an endomembrane damage dependent way. This work uncovers an inter-organelle communication pathway, providing a general mechanism by which macrophages undergo mitochondrial metabolic reprograming after endomembrane damage.

DOI: https://doi.org/10.1038/s41467-022-34632-8
EMBO J. 2022 Nov 29. e111389

The lysosomal Ragulator complex activates NLRP3 inflammasome in vivo via HDAC6.

Kohei Tsujimoto, Tatsunori Jo, Daiki Nagira, Hachiro Konaka, Jeong Hoon Park, Shin-Ichiro Yoshimura, Akinori Ninomiya, Fuminori Sugihara, Takehiro Hirayama, Eri Itotagawa, Yusei Matsuzaki, Yuki Takaichi, Wataru Aoki, Shotaro Saita, Shuhei Nakamura, Andrea Ballabio, Shigeyuki Nada, Masato Okada, Hyota Takamatsu, Atsushi Kumanogoh.

  The cellular activation of the NLRP3 inflammasome is spatiotemporally orchestrated by various organelles, but whether lysosomes contribute to this process remains unclear. Here, we show the vital role of the lysosomal membrane-tethered Ragulator complex in NLRP3 inflammasome activation. Deficiency of Lamtor1, an essential component of the Ragulator complex, abrogated NLRP3 inflammasome activation in murine macrophages and human monocytic cells. Myeloid-specific Lamtor1-deficient mice showed marked attenuation of NLRP3-associated inflammatory disease severity, including LPS-induced sepsis, alum-induced peritonitis, and monosodium urate (MSU)-induced arthritis. Mechanistically, Lamtor1 interacted with both NLRP3 and histone deacetylase 6 (HDAC6). HDAC6 enhances the interaction between Lamtor1 and NLRP3, resulting in NLRP3 inflammasome activation. DL-all-rac-α-tocopherol, a synthetic form of vitamin E, inhibited the Lamtor1-HDAC6 interaction, resulting in diminished NLRP3 inflammasome activation. Further, DL-all-rac-α-tocopherol alleviated acute gouty arthritis and MSU-induced peritonitis. These results provide novel insights into the role of lysosomes in the activation of NLRP3 inflammasomes by the Ragulator complex.

Keywords:  HDAC6; NLRP3 inflammasome; Ragulator complex; α-tocopherol

DOI:  https://doi.org/10.15252/embj.2022111389
Cell Prolif. 2022 Nov 30. e13368

G3BP1 coordinates lysophagy activity to protect against compression-induced cell ferroptosis during intervertebral disc degeneration.

Shuai Li, Zhiwei Liao, Huipeng Yin, Ouyang Liu, Wenbin Hua, Xinghuo Wu, Yukun Zhang, Yong Gao, Cao Yang.

Lysophagy is a form of selective autophagy to remove unwanted lysosomes. However, its role in the pathogenesis of intervertebral disc degeneration (IDD) remains unclear. We intended to investigate the relationship between lysophagy and ferroptosis, as well as the potential involved molecules during IDD. Human nucleus pulposus (NP) cells were obtained from clinical patients. The protein levels, protein colocalization and cellular reactive oxygen species levels were assessed by western blotting, immunofluorescence analysis, immunoprecipitation and flow cytometry, respectively. The in vivo experiments were conducted based on the needle puncture-induced IDD model in rats. Compression pressure induces the lysophagy inactivation and lysosomal damage, resulting in iron overload and ferroptosis in human NP cells. Notably, Ras GTPase-activating protein-binding proteins 1 (G3BP1) resides at lysosomes to coordinate lysophagy activity mainly via the function of G3BP1/TSC2 complex. Dysfunction of G3BP1/TSC2 complex accelerates the lysosomal damage and ferroptosis in NP cells. Besides, inhibition of mTOR signalling ameliorates lysosomal damage and protects against cell ferroptosis. The in vivo experiments also demonstrate that the G3BP1/mTOR signalling is involved in the progression of IDD. These findings illustrate the relationship between lysophagy and compression-induced cell ferroptosis. It also indicates the positive role of G3BP1 and may provide potential targets for IDD treatment.

DOI: https://doi.org/10.1111/cpr.13368