bims-lypmec 2023-09-17 papers

Issue of 2023‒09‒17
six papers selected by
Satoru Kobayashi, New York Institute of Technology

Sci Adv. 2023 Sep 15. 9(37): eadd9084

Codependencies of mTORC1 signaling and endolysosomal actin structures.

Amulya Priya, Sandra Antoine-Bally, Anne-Sophie Macé, Pedro Monteiro, Valentin Sabatet, David Remy, Florent Dingli, Damarys Loew, Constantinos Demetriades, Alexis M Gautreau, Philippe Chavrier.

The mechanistic target of rapamycin complex 1 (mTORC1) is part of the amino acid sensing machinery that becomes activated on the endolysosomal surface in response to nutrient cues. Branched actin generated by WASH and Arp2/3 complexes defines endolysosomal microdomains. Here, we find mTORC1 components in close proximity to endolysosomal actin microdomains. We investigated for interactors of the mTORC1 lysosomal tether, RAGC, by proteomics and identified multiple actin filament capping proteins and their modulators. Perturbation of RAGC function affected the size of endolysosomal actin, consistent with a regulation of actin filament capping by RAGC. Reciprocally, the pharmacological inhibition of actin polymerization or alteration of endolysosomal actin obtained upon silencing of WASH or Arp2/3 complexes impaired mTORC1 activity. Mechanistically, we show that actin is required for proper association of RAGC and mTOR with endolysosomes. This study reveals an unprecedented interplay between actin and mTORC1 signaling on the endolysosomal system.

DOI: https://doi.org/10.1126/sciadv.add9084

EMBO J. 2023 Sep 15. e113928

TFEB and TFE3 control glucose homeostasis by regulating insulin gene expression.

Adrien Pasquier, Nunzia Pastore, Luca D'Orsi, Rita Colonna, Alessandra Esposito, Veronica Maffia, Rossella De Cegli, Margherita Mutarelli, Susanna Ambrosio, Gennaro Tufano, Antonio Grimaldi, Marcella Cesana, Davide Cacchiarelli, Nathalie Delalleau, Gennaro Napolitano, Andrea Ballabio.

To fulfill their function, pancreatic beta cells require precise nutrient-sensing mechanisms that control insulin production. Transcription factor EB (TFEB) and its homolog TFE3 have emerged as crucial regulators of the adaptive response of cell metabolism to environmental cues. Here, we show that TFEB and TFE3 regulate beta-cell function and insulin gene expression in response to variations in nutrient availability. We found that nutrient deprivation in beta cells promoted TFEB/TFE3 activation, which resulted in suppression of insulin gene expression. TFEB overexpression was sufficient to inhibit insulin transcription, whereas beta cells depleted of both TFEB and TFE3 failed to suppress insulin gene expression in response to amino acid deprivation. Interestingly, ChIP-seq analysis showed binding of TFEB to super-enhancer regions that regulate insulin transcription. Conditional, beta-cell-specific, Tfeb-overexpressing, and Tfeb/Tfe3 double-KO mice showed severe alteration of insulin transcription, secretion, and glucose tolerance, indicating that TFEB and TFE3 are important physiological mediators of pancreatic function. Our findings reveal a nutrient-controlled transcriptional mechanism that regulates insulin production, thus playing a key role in glucose homeostasis at both cellular and organismal levels.

Keywords: TFEB; beta cells; glucose homeostasis; insulin; mTORC1

DOI: https://doi.org/10.15252/embj.2023113928

Drug Discov Today. 2023 Sep 12. pii: S1359-6446(23)00283-0. [Epub ahead of print] 103767

Hongmei Zheng, Gangjian Li, Jingli Min, Xiangwei Xu, Wenhai Huang.

Recently, targeted protein degradation technologies based on lysosomal pathways have been developed. Lysosome-based targeted protein degradation technology has a broad range of substrates and the potential to degrade intracellular and extracellular proteins, protein aggregates, damaged organelles and non-protein molecules. Thus, they hold great promise for drug R&D. This study has focused on the biogenesis of lysosomes, their basic functions, lysosome-associated diseases and targeted protein degradation technologies through the lysosomal pathway. In addition, we thoroughly examine the potential applications and limitations of this technology and engage in insightful discussions on potential avenues for future research. Our primary objective is to foster preclinical research on this technology and facilitate its successful clinical implementation.

Keywords: Lysosome; damaged organelles; extracellular proteins; protein aggregates; protein degradation technology

DOI: https://doi.org/10.1016/j.drudis.2023.103767

Biochem Biophys Res Commun. 2023 Sep 06. pii: S0006-291X(23)01042-2. [Epub ahead of print]679 145-159

Role of lysosomes in insulin signaling and glucose uptake in cultured rat podocytes.

Patrycja Rachubik, Dorota Rogacka, Irena Audzeyenka, Marlena Typiak, Magdalena Wysocka, Maria Szrejder, Adam Lesner, Agnieszka Piwkowska.

Podocytes are sensitive to insulin, which governs the functional and structural integrity of podocytes that are essential for proper function of the glomerular filtration barrier. Lysosomes are acidic organelles that are implicated in regulation of the insulin signaling pathway. Cathepsin D (CTPD) and lysosome-associated membrane protein 1 (LAMP1) are major lysosomal proteins that reflect the functional state of lysosomes. However, the effect of insulin on lysosome activity and role of lysosomes in the regulation of insulin-dependent glucose uptake in podocytes are unknown. Our studies showed that the short-term incubation of podocytes with insulin decreased LAMP1 and CTPD mRNA levels. Insulin and bafilomycin A1 reduced both the amounts of LAMP1 and CTPD proteins and activity of CTPD, which were associated with a decrease in the fluorescence intensity of lysosomes that were labeled with LysoTracker. Bafilomycin A1 inhibited insulin-dependent endocytosis of the insulin receptor and increased the amounts of the insulin receptor and glucose transporter 4 on the cell surface of podocytes. Bafilomycin A1 also inhibited insulin-dependent glucose uptake despite an increase in the amount of glucose transporter 4 in the plasma membrane of podocytes. These results suggest that lysosomes are signaling hubs that may be involved in the coupling of insulin signaling with the regulation of glucose uptake in podocytes. The dysregulation of this mechanism can lead to the dysfunction of podocytes and development of insulin resistance.

Keywords: Bafilomycin A1; Cathepsin D; Glucose uptake; Insulin; Lysosome; Podocyte

DOI: https://doi.org/10.1016/j.bbrc.2023.09.012

Nat Metab. 2023 Sep 11.

Dynamic lipidome alterations associated with human health, disease and ageing.

Daniel Hornburg, Si Wu, Mahdi Moqri, Xin Zhou, Kevin Contrepois, Nasim Bararpour, Gavin M Traber, Baolong Su, Ahmed A Metwally, Monica Avina, Wenyu Zhou, Jessalyn M Ubellacker, Tejaswini Mishra, Sophia Miryam Schüssler-Fiorenza Rose, Paula B Kavathas, Kevin J Williams, Michael P Snyder.

Lipids can be of endogenous or exogenous origin and affect diverse biological functions, including cell membrane maintenance, energy management and cellular signalling. Here, we report >800 lipid species, many of which are associated with health-to-disease transitions in diabetes, ageing and inflammation, as well as cytokine-lipidome networks. We performed comprehensive longitudinal lipidomic profiling and analysed >1,500 plasma samples from 112 participants followed for up to 9 years (average 3.2 years) to define the distinct physiological roles of complex lipid subclasses, including large and small triacylglycerols, ester- and ether-linked phosphatidylethanolamines, lysophosphatidylcholines, lysophosphatidylethanolamines, cholesterol esters and ceramides. Our findings reveal dynamic changes in the plasma lipidome during respiratory viral infection, insulin resistance and ageing, suggesting that lipids may have roles in immune homoeostasis and inflammation regulation. Individuals with insulin resistance exhibit disturbed immune homoeostasis, altered associations between lipids and clinical markers, and accelerated changes in specific lipid subclasses during ageing. Our dataset based on longitudinal deep lipidome profiling offers insights into personalized ageing, metabolic health and inflammation, potentially guiding future monitoring and intervention strategies.

DOI: https://doi.org/10.1038/s42255-023-00880-1