bims-lypmec Biomed News
on Lysosomal positioning and metabolism in cardiomyocytes
Issue of 2022–12–25
ten papers selected by
Satoru Kobayashi, New York Institute of Technology
  1. mTORC1 takes control of lysosomal lipid breakdown.
  2. mTORC1 regulates a lysosome-dependent adaptive shift in intracellular lipid species.
  3. The endo-lysosomal regulatory protein BLOC1S1 modulates hepatic lysosomal content and lysosomal lipolysis.
  4. Orchestration of selective autophagy by cargo receptors.
  5. Blocking AMPK β1 myristoylation enhances AMPK activity and protects mice from high-fat diet-induced obesity and hepatic steatosis.
  6. Toosendanin Induces Hepatocyte Damage by Inhibiting Autophagic Flux via TFEB-Mediated Lysosomal Dysfunction.
  7. The fates of internalized NaV1.7 channels in sensory neurons: retrograde co-transport with other ion channels, axon-specific recycling, and degradation.
  8. Live-cell imaging and analysis of actin-mediated mitochondrial fission.
  9. Interplay between Myokine Profile and Glycemic Control in Type 2 Diabetes Mellitus Patients with Heart Failure.
  10. CD20/TNFR1 dual-targeting antibody enhances lysosome rupture-mediated cell death in B cell lymphoma.
  1. Nat Metab. 2022 Dec;4(12): 1620-1622
    mTORC1 takes control of lysosomal lipid breakdown.
    Laura Tribouillard, Mathieu Laplante.
      
    DOI:  https://doi.org/10.1038/s42255-022-00702-w
  2. Nat Metab. 2022 Dec;4(12): 1792-1811
    mTORC1 regulates a lysosome-dependent adaptive shift in intracellular lipid species.
    Aaron M Hosios, Meghan E Wilkinson, Molly C McNamara, Krystle C Kalafut, Margaret E Torrence, John M Asara, Brendan D Manning.
      The mechanistic target of rapamycin complex 1 (mTORC1) senses and relays environmental signals from growth factors and nutrients to metabolic networks and adaptive cellular systems to control the synthesis and breakdown of macromolecules; however, beyond inducing de novo lipid synthesis, the role of mTORC1 in controlling cellular lipid content remains poorly understood. Here we show that inhibition of mTORC1 via small molecule inhibitors or nutrient deprivation leads to the accumulation of intracellular triglycerides in both cultured cells and a mouse tumor model. The elevated triglyceride pool following mTORC1 inhibition stems from the lysosome-dependent, but autophagy-independent, hydrolysis of phospholipid fatty acids. The liberated fatty acids are available for either triglyceride synthesis or β-oxidation. Distinct from the established role of mTORC1 activation in promoting de novo lipid synthesis, our data indicate that mTORC1 inhibition triggers membrane phospholipid trafficking to the lysosome for catabolism and an adaptive shift in the use of constituent fatty acids for storage or energy production.
    DOI:  https://doi.org/10.1038/s42255-022-00706-6
  3. Biochem Biophys Res Commun. 2022 Dec 14. pii: S0006-291X(22)01703-X. [Epub ahead of print]642 1-10
    The endo-lysosomal regulatory protein BLOC1S1 modulates hepatic lysosomal content and lysosomal lipolysis.
    Kaiyuan Wu, Jizhong Zou, Michael N Sack.
      BLOC1S1 is a common component of BLOC and BORC multiprotein complexes which play distinct roles in endosome and lysosome biology. Recent human mutations in BLOC1S1 associate with juvenile leukodystrophy. As leukodystrophy is linked to perturbed lysosomal lipid storage we explored whether BLOC1S1 itself modulates this biology. Given the central role of the liver in lipid storage, our investigations were performed in hepatocyte specific liver bloc1s1 knockout (LKO) mice and in human hepatocyte-like lines (HLCs) derived from inducible pluripotential stem cells (iPSCs) from a juvenile leukodystrophy subject's with bloc1s1 mutations and from isogenic corrected iPSCs. Here we show that hepatocyte lipid stores are diminished in parallel with increased lysosomal content, increased lysosomal lipid uptake and lipolysis in LKO mice. The lysosomal lipolysis program was independent of macro- and chaperone-mediated lipophagy but dependent on cellular lysosome content. In parallel, genetic induction of lysosomal biogenesis in a transformed hepatocyte cell line replicated depletion of intracellular lipid stores. Interestingly bloc1s1 mutant and isogenic corrected HLCs both showed normal lysosomal enzyme activity. However, relative to the isogenic corrected HLCs, mutant bloc1s1 HLCs showed reduced lysosomal content and increased lipid storage. Together these data show distinct phenotypes in human mutant HLCs compared to murine knockout cells. At the same time, human blcs1s1 mutation and murine hepatocyte bloc1s1 depletion disrupt lysosome content and the cellular lipid storage. These data support that BLOC1S1 modulates lysosome content and lipid handling independent of autophagy and show that lysosomal lipolysis is dependent on the cellular content of functional lysosomes.
    Keywords:  BLOC1S1; Hepatic lipid droplets; Lysosomal lipolysis; Lysosome
    DOI:  https://doi.org/10.1016/j.bbrc.2022.12.038
  4. Curr Biol. 2022 Dec 19. pii: S0960-9822(22)01758-4. [Epub ahead of print]32(24): R1357-R1371
    Orchestration of selective autophagy by cargo receptors.
    Elias Adriaenssens, Luca Ferrari, Sascha Martens.
      Cellular homeostasis requires the swift and specific removal of damaged material. Selective autophagy represents a major pathway for the degradation of such cargo material. This is achieved by the sequestration of the cargo within double-membrane vesicles termed autophagosomes, which form de novo around the cargo and subsequently deliver their content to lysosomes for degradation. The importance of selective autophagy is exemplified by the various neurodegenerative diseases associated with defects in this pathway, including Parkinson's disease, amyotrophic lateral sclerosis, and frontotemporal dementia. It has become evident that cargo receptors are acting as Swiss army knives in selective autophagy by recognizing the cargo, orchestrating the recruitment of the machinery for autophagosome biogenesis, and closely aligning the membrane with the cargo. Furthermore, cargo receptors sequester ubiquitinated proteins into larger condensates upstream of autophagy induction. Here, we review recent insights into the mechanisms of action of cargo receptors in selective autophagy by focusing on the roles of sequestosome-like cargo receptors in the degradation of misfolded, ubiquitinated proteins and damaged mitochondria. We also highlight at which steps defects in their function result in the accumulation of harmful material and how this knowledge may guide the design of future therapies.
    DOI:  https://doi.org/10.1016/j.cub.2022.11.002
  5. Cell Rep. 2022 Dec 20. pii: S2211-1247(22)01758-2. [Epub ahead of print]41(12): 111862
    Blocking AMPK β1 myristoylation enhances AMPK activity and protects mice from high-fat diet-induced obesity and hepatic steatosis.
    Katyayanee Neopane, Natalie Kozlov, Florentina Negoita, Lisa Murray-Segal, Robert Brink, Ashfaqul Hoque, Ashley J Ovens, Gavin Tjin, Luke M McAloon, Dingyi Yu, Naomi X Y Ling, Matthew J Sanders, Jonathan S Oakhill, John W Scott, Gregory R Steinberg, Kim Loh, Bruce E Kemp, Kei Sakamoto, Sandra Galic.
      AMP-activated protein kinase (AMPK) is a master regulator of cellular energy homeostasis and a therapeutic target for metabolic diseases. Co/post-translational N-myristoylation of glycine-2 (Gly2) of the AMPK β subunit has been suggested to regulate the distribution of the kinase between the cytosol and membranes through a "myristoyl switch" mechanism. However, the relevance of AMPK myristoylation for metabolic signaling in cells and in vivo is unclear. Here, we generated knockin mice with a Gly2-to-alanine point mutation of AMPKβ1 (β1-G2A). We demonstrate that non-myristoylated AMPKβ1 has reduced stability but is associated with increased kinase activity and phosphorylation of the Thr172 activation site in the AMPK α subunit. Using proximity ligation assays, we show that loss of β1 myristoylation impedes colocalization of the phosphatase PPM1A/B with AMPK in cells. Mice carrying the β1-G2A mutation have improved metabolic health with reduced adiposity, hepatic lipid accumulation, and insulin resistance under conditions of high-fat diet-induced obesity.
    Keywords:  AMPK; CP: Metabolism; adiposity; myristoylation; phosphatase; signal transduction; steatosis
    DOI:  https://doi.org/10.1016/j.celrep.2022.111862
  6. Pharmaceuticals (Basel). 2022 Dec 03. pii: 1509. [Epub ahead of print]15(12):
    Toosendanin Induces Hepatocyte Damage by Inhibiting Autophagic Flux via TFEB-Mediated Lysosomal Dysfunction.
    Li Luo, Yonghong Liang, Yuanyuan Fu, Zhiyuan Liang, Jinfen Zheng, Jie Lan, Feihai Shen, Zhiying Huang.
      Toosendanin (TSN) is a triterpenoid from the fruit or bark of Melia toosendan Sieb et Zucc, which has clear antitumor and insecticidal activities, but it possesses limiting hepatotoxicity in clinical application. Autophagy is a degradation and recycling mechanism to maintain cellular homeostasis, and it also plays an essential role in TSN-induced hepatotoxicity. Nevertheless, the specific mechanism of TSN on autophagy-related hepatotoxicity is still unknown. The hepatotoxicity of TSN in vivo and in vitro was explored in this study. It was found that TSN induced the upregulation of the autophagy-marker microtubule-associated proteins 1A/1B light chain 3B (LC3B) and P62, the accumulation of autolysosomes, and the inhibition of autophagic flux. The middle and late stages of autophagy were mainly studied. The data showed that TSN did not affect the fusion of autophagosomes and lysosomes but significantly inhibited the acidity, the degradation capacity of lysosomes, and the expression of hydrolase cathepsin B (CTSB). The activation of autophagy could alleviate TSN-induced hepatocyte damage. TSN inhibited the expression of transcription factor EB (TFEB), which is a key transcription factor for many genes of autophagy and lysosomes, such as CTSB, and overexpression of TFEB alleviated the autophagic flux blockade caused by TSN. In summary, TSN caused hepatotoxicity by inhibiting TFEB-lysosome-mediated autophagic flux and activating autophagy by rapamycin (Rapa), which could effectively alleviate TSN-induced hepatotoxicity, indicating that targeting autophagy is a new strategy to intervene in the hepatotoxicity of TSN.
    Keywords:  TFEB; autophagic flux; autophagy; hepatotoxicity; lysosome; toosendanin (TSN)
    DOI:  https://doi.org/10.3390/ph15121509
  7. J Biol Chem. 2022 Dec 17. pii: S0021-9258(22)01259-5. [Epub ahead of print] 102816
    The fates of internalized NaV1.7 channels in sensory neurons: retrograde co-transport with other ion channels, axon-specific recycling, and degradation.
    Grant P Higerd-Rusli, Sidharth Tyagi, Shujun Liu, Fadia B Dib-Hajj, Stephen G Waxman, Sulayman D Dib-Hajj.
      Neuronal function relies on the maintenance of appropriate levels of various ion channels at the cell membrane, which is accomplished by balancing secretory, degradative, and recycling pathways. Neuronal function further depends on membrane specialization through polarized distribution of specific proteins to distinct neuronal compartments such as axons. Voltage-gated sodium channel NaV1.7, a threshold channel for firing action potentials in nociceptors, plays a major role in human pain, and its abundance in the plasma membrane is tightly regulated. We have recently characterized the anterograde axonal trafficking of NaV1.7 channels in Rab6A-positive vesicles, but the fate of internalized channels is not known. Membrane proteins which have undergone endocytosis can be directed into multiple pathways including those for degradation, recycling to the membrane, and transcytosis. Here we demonstrate NaV1.7 endocytosis and dynein-dependent retrograde trafficking in Rab7-containing late endosomes together with other axonal membrane proteins using real-time imaging of live neurons. We show that some internalized NaV1.7 channels are delivered to lysosomes within the cell body, and that there is no evidence for NaV1.7 transcytosis. In addition, we show that NaV1.7 is recycled specifically to the axonal membrane as opposed to the soma membrane, suggesting a novel mechanism for the development of neuronal polarity. Together, these results shed light on the mechanisms by which neurons maintain excitable membranes and may inform efforts to target ion channel trafficking for the treatment of disorders of excitability.
    Keywords:  Sodium channel; endocytosis; intracellular trafficking; membrane recycling; pain
    DOI:  https://doi.org/10.1016/j.jbc.2022.102816
  8. STAR Protoc. 2022 Dec 20. pii: S2666-1667(22)00838-3. [Epub ahead of print]4(1): 101958
    Live-cell imaging and analysis of actin-mediated mitochondrial fission.
    Daisuke Shimura, Robin M Shaw.
      Current approaches, such as fixed-cell imaging or single-snapshot imaging, are insufficient to capture cytoskeleton-mediated mitochondrial fission. Here, we present a protocol to capture actin-mediated mitochondrial fission using high-resolution time-lapse imaging. We describe steps starting from cell preparation and mitochondria labeling through to live-cell imaging and final analysis. This approach is also applicable for analysis of multiple cytoskeleton-mediated organelle events such as vesicle trafficking, membrane fusion, and endocytic events in live cells. For complete details on the use and execution of this protocol, please refer to Shimura et al. (2021).1.
    Keywords:  Cell Biology; Microscopy; Molecular Biology
    DOI:  https://doi.org/10.1016/j.xpro.2022.101958
  9. Diagnostics (Basel). 2022 Nov 24. pii: 2940. [Epub ahead of print]12(12):
    Interplay between Myokine Profile and Glycemic Control in Type 2 Diabetes Mellitus Patients with Heart Failure.
    Alexander A Berezin, Zeljko Obradovic, Evgen V Novikov, Elke Boxhammer, Michael Lichtenauer, Alexander E Berezin.
      Type 2 diabetes mellitus (T2DM) remains a powerful predictor of progressive heart failure (HF), but it is not clear whether altered glycemic control interferes with HF progression via an impaired profile of circulating myokines. The aim was to investigate plausible effects of glucose control on a myokine signature in T2DM patients affected by chronic HF. We selected 372 T2DM patients from the local database and finally included 314 individuals suffering from chronic HF and subdivided them into two groups according to glycosylated hemoglobin (HbA1c) levels (<6.9% and ≥7.0%). Echocardiography and Doppler examinations along with biomarker measurements were performed at the baseline of the study. The results showed that irisin levels were significantly lower in patients with HbA1c ≥ 7.0% than in those with HbAc1 < 6.9%, whereas concentrations of apelin, myostatin and adropin did not significantly differ between these two groups. We also identified numerous predictors of poor glycemic control, but only N-terminal brain natriuretic propeptide (odds ratio [OR] = 1.07; 95% confidence interval [CI] = 1.02-1.10, p = 0.04) and irisin (OR = 1.09; 95% CI = 1.04-1.17, p = 0.001) remained independent predictors of the dependent variable. In conclusion, we found that decreased levels of irisin were associated with poor glycemic control in T2DM patients with HF regardless of clinical conditions and other biomarkers.
    Keywords:  adropin; apelin; biomarkers; heart failure; irisin; myokines; myostatin; prediction; type 2 diabetes mellitus
    DOI:  https://doi.org/10.3390/diagnostics12122940
  10. Cancer Immunol Immunother. 2022 Dec 19.
    CD20/TNFR1 dual-targeting antibody enhances lysosome rupture-mediated cell death in B cell lymphoma.
    Jeong Ryeol Kim, Donghyuk Lee, Yerim Kim, Joo Young Kim.
      Obinutuzumab is a therapeutic antibody for B cell non-Hodgkin's Lymphoma (BNHL), which is a glyco-engineered anti-CD20 antibody with enhanced antibody-dependent cellular cytotoxicity (ADCC) and causes binding-induced direct cell death (DCD) through lysosome membrane permeabilization (LMP). Tumour necrosis factor receptor 1 (TNFR1), a pro-inflammatory death receptor, also evokes cell death, partly through lysosomal rupture. As both obinutuzumab- and TNFR1-induced cell deaths are mediated by LMP and combining TNFR1 and obinutuzumab can amplify LMP-mediated cell death, we made dual-targeting antibody for CD20 and TNFR1 to enhance DCD of obinutuzumab.Obinutuzumab treatment-induced CD20 and TNFR1 colocalisation, and TNFR1-overexpressing cells showed increased obinutuzumab-induced DCD. Two targeting modes, anti-CD20/TNFR1 bispecific antibodies (bsAbs), and obinutuzumab-TNFα fusion proteins (OBI-TNFαWT and OBI-TNFαMUT), were designed to cluster CD20 and TNFR1 on the plasma membrane. OBI-TNFαWT and OBI-TNFαMUT showed significantly enhanced LMP, DCD, and ADCC compared with that induced by obinutuzumab. TNFR1 expression is upregulated in many BNHL subtypes compared to that in normal B cells; OBI-TNFαMUT specifically increased DCD and ADCC in a B cell lymphoma cell line overexpressing TNFR1. Further, OBI-TNFαMUT blocked NF-κB activation in the presence of TNF-α, implying that it can antagonise the proliferative role of TNF-α in cancers.Our study suggests that dual targeting of CD20 and TNFR1 can be a new therapeutic strategy for improving BNHL treatment. The OBI-TNFαMUT fusion protein enhances DCD and ADCC and prevents the proliferating effect of TNFα signalling; therefore, it may provide precision treatment for patients with BNHL, especially those with upregulated TNFR1 expression.
    Keywords:  Antibody binding-induced cell death; BNHL (B cell non-Hodgkin’s lymphoma); Bispecific or fusion proteins; Obinutuzumab; TNFR1
    DOI:  https://doi.org/10.1007/s00262-022-03344-9
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