bims-lypmec 2023-09-10 papers

bims-lypmec

Biomed News

on Lysosomal positioning and metabolism in cardiomyocytes

Issue of 2023‒09‒10
seven papers selected by
Satoru Kobayashi, New York Institute of Technology

Lysosomes mediate the mitochondrial UPR via mTORC1-dependent ATF4 phosphorylation.
TFEB regulates cellular labile iron and prevents ferroptosis in a TfR1-dependent manner.
CCDC50 promotes tumor growth through regulation of lysosome homeostasis.
Lysosome-targeted fluorescent probes: Design mechanism and biological applications.
Orchestrating vesicular and nonvesicular membrane dynamics by intrinsically disordered proteins.
Differential intracellular management of fatty acids impacts on metabolic stress-stimulated glucose uptake in cardiomyocytes.
TRAP1 inhibits MARCH5-mediated MIC60 degradation to alleviate mitochondrial dysfunction and apoptosis of cardiomyocytes under diabetic conditions.

Cell Discov. 2023 Sep 07. 9(1): 92

Lysosomes mediate the mitochondrial UPR via mTORC1-dependent ATF4 phosphorylation.

Terytty Yang Li, Qi Wang, Arwen W Gao, Xiaoxu Li, Yu Sun, Adrienne Mottis, Minho Shong, Johan Auwerx.

Lysosomes are central platforms for not only the degradation of macromolecules but also the integration of multiple signaling pathways. However, whether and how lysosomes mediate the mitochondrial stress response (MSR) remain largely unknown. Here, we demonstrate that lysosomal acidification via the vacuolar H+-ATPase (v-ATPase) is essential for the transcriptional activation of the mitochondrial unfolded protein response (UPRmt). Mitochondrial stress stimulates v-ATPase-mediated lysosomal activation of the mechanistic target of rapamycin complex 1 (mTORC1), which then directly phosphorylates the MSR transcription factor, activating transcription factor 4 (ATF4). Disruption of mTORC1-dependent ATF4 phosphorylation blocks the UPRmt, but not other similar stress responses, such as the UPRER. Finally, ATF4 phosphorylation downstream of the v-ATPase/mTORC1 signaling is indispensable for sustaining mitochondrial redox homeostasis and protecting cells from ROS-associated cell death upon mitochondrial stress. Thus, v-ATPase/mTORC1-mediated ATF4 phosphorylation via lysosomes links mitochondrial stress to UPRmt activation and mitochondrial function resilience.

DOI: https://doi.org/10.1038/s41421-023-00589-1
Free Radic Biol Med. 2023 Sep 06. pii: S0891-5849(23)00622-6. [Epub ahead of print]

TFEB regulates cellular labile iron and prevents ferroptosis in a TfR1-dependent manner.

Leilei Chen, Yue Ma, Xizhen Ma, Lin Liu, Xianhui Jv, Ang Li, Qingqing Shen, Wenting Jia, Le Qu, Limin Shi, Junxia Xie.

  Autophagy is a major clearance pathway for misfolded α-synuclein which promotes ferroptosis through NCOA4-mediated ferritin degradation. The regulation of these two processes to achieve improved neuroprotection in Parkinson's disease (PD) must be elucidated. Transcription factor EB (TFEB) is a master regulator of both autophagy and lysosome biogenesis, and lysosomes are important cellular iron storage organelles; however, the role of TFEB in ferroptosis and iron metabolism remains unclear. In this study, TFEB overexpression promoted the clearance of misfolded α-synuclein and prevented ferroptosis and iron overload. TFEB overexpression up-regulated transferrin receptor 1 (TfR1) synthesis and increased the localization of TfR1 in the lysosome, facilitating lysosomal iron import and transient lysosomal iron storage. TFEB overexpression increased the levels of cellular iron-safe storage proteins (both ferritin light and heavy chains). These functions in iron metabolism maintain the cellular labile iron at a low level and electrical activity, even under iron overload conditions. Notably, lower levels of cellular labile iron and the upregulation of ferritin light and heavy chains were reversed after TfR1 knockdown in cells overexpressing TFEB, indicating that TFEB regulates cellular labile iron and suppresses ferroptosis in a TfR1 dependent manner. Taken together, this evidence of the regulation of iron metabolism enriches our understanding of the function of TFEB. In addition, TFEB overexpression protects against ferroptosis and iron overload and provides a new direction and perspective for autophagy regulation in PD.

Keywords:  Ferroptosis; Iron metabolism; Lysosome; TFEB; TfR1

DOI:  https://doi.org/10.1016/j.freeradbiomed.2023.09.004
EMBO Rep. 2023 Sep 06. e56948

CCDC50 promotes tumor growth through regulation of lysosome homeostasis.

Penghui Jia, Tian Tian, Zibo Li, Yicheng Wang, Yuxin Lin, Weijie Zeng, Yu Ye, Miao He, Xiangrong Ni, Ji'an Pan, Xiaonan Dong, Jian Huang, Chun-Mei Li, Deyin Guo, Panpan Hou.

  The maintenance of lysosome homeostasis is crucial for cell growth. Lysosome-dependent degradation and metabolism sustain tumor cell survival. Here, we demonstrate that CCDC50 serves as a lysophagy receptor, promoting tumor progression and invasion by controlling lysosomal integrity and renewal. CCDC50 monitors lysosomal damage, recognizes galectin-3 and K63-linked polyubiquitination on damaged lysosomes, and specifically targets them for autophagy-dependent degradation. CCDC50 deficiency causes the accumulation of ruptured lysosomes, impaired autophagic flux, and superfluous reactive oxygen species, consequently leading to cell death and tumor suppression. CCDC50 expression is associated with malignancy, progression to metastasis, and poor overall survival in human melanoma. Targeting CCDC50 suppresses tumor growth and lung metastasis, and enhances the effect of BRAFV600E inhibition. Thus, we demonstrate critical roles of CCDC50-mediated clearance of damaged lysosomes in supporting tumor growth, hereby identifying a potential therapeutic target of melanoma.

Keywords:  CCDC50; cell death; lysophagy; lysosome damage; melanoma

DOI:  https://doi.org/10.15252/embr.202356948
Bioorg Chem. 2023 Sep 03. pii: S0045-2068(23)00493-5. [Epub ahead of print]140 106832

Lysosome-targeted fluorescent probes: Design mechanism and biological applications.

Xiangning Duan, Qin Tong, Chengxiao Fu, Linxi Chen.

  As an integral organelle in the eukaryote, the lysosome is the degradation center and metabolic signal center in living cells, and partakes in significant physiological processes such as autophagy, cell death and cellular senescence. Fluorescent probe has become a favorite tool for studying organelles and their chemical microenvironments because of its high specificity and non-destructive merits. Over recent years, it has been reported that increasingly new lysosome-targeted probes play a major role in the diagnosis and monitor of diseases, in particular cancer and neurodegenerative diseases. In order to deepen the relevant research on lysosome, it is challenging and inevitability to design novel lysosomal targeting probes. This review first introduces the concepts of lysosome and its closely related biological activities, and then introduces the fluorescent probes for lysosome in detail according to different detection targets, including targeting mechanism, biological imaging, and application in diseases. Finally, we summarize the specific challenges and discuss the future development direction facing the current lysosome-targeted fluorescent probes. We hope that this review can help biologists grasp the application of fluorescent probes and broaden the research ideas of researchers targeting fluorescent probes so as to design more accurate and functional probes for application in diseases.

Keywords:  Cell imaging; Fluorescent probes; Lysosome; Sensing microenvironment

DOI:  https://doi.org/10.1016/j.bioorg.2023.106832
EMBO Rep. 2023 Sep 08. e57758

Orchestrating vesicular and nonvesicular membrane dynamics by intrinsically disordered proteins.

Stephan J Sigrist, Volker Haucke.

  Compartmentalization by membranes is a common feature of eukaryotic cells and serves to spatiotemporally confine biochemical reactions to control physiology. Membrane-bound organelles such as the endoplasmic reticulum (ER), the Golgi complex, endosomes and lysosomes, and the plasma membrane, continuously exchange material via vesicular carriers. In addition to vesicular trafficking entailing budding, fission, and fusion processes, organelles can form membrane contact sites (MCSs) that enable the nonvesicular exchange of lipids, ions, and metabolites, or the secretion of neurotransmitters via subsequent membrane fusion. Recent data suggest that biomolecule and information transfer via vesicular carriers and via MCSs share common organizational principles and are often mediated by proteins with intrinsically disordered regions (IDRs). Intrinsically disordered proteins (IDPs) can assemble via low-affinity, multivalent interactions to facilitate membrane tethering, deformation, fission, or fusion. Here, we review our current understanding of how IDPs drive the formation of multivalent protein assemblies and protein condensates to orchestrate vesicular and nonvesicular transport with a special focus on presynaptic neurotransmission. We further discuss how dysfunction of IDPs causes disease and outline perspectives for future research.

Keywords:  intrinsically disordered proteins; membrane contact sites; neurotransmission; synapse; vesicular and nonvesicular transport

DOI:  https://doi.org/10.15252/embr.202357758
Sci Rep. 2023 Sep 08. 13(1): 14805

Differential intracellular management of fatty acids impacts on metabolic stress-stimulated glucose uptake in cardiomyocytes.

Ettore Vanni, Karina Lindner, Anne-Claude Gavin, Christophe Montessuit.

Stimulation of glucose uptake in response to ischemic metabolic stress is important for cardiomyocyte function and survival. Chronic exposure of cardiomyocytes to fatty acids (FA) impairs the stimulation of glucose uptake, whereas induction of lipid droplets (LD) is associated with preserved glucose uptake. However, the mechanisms by which LD induction prevents glucose uptake impairment remain elusive. We induced LD with either tetradecanoyl phorbol acetate (TPA) or 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside (AICAR). Triacylglycerol biosynthesis enzymes were inhibited in cardiomyocytes exposed to FA ± LD inducers, either upstream (glycerol-3-phosphate acyltransferases; GPAT) or downstream (diacylglycerol acyltransferases; DGAT) of the diacylglycerol step. Although both inhibitions reduced LD formation in cardiomyocytes treated with FA and LD inducers, only DGAT inhibition impaired metabolic stress-stimulated glucose uptake. DGAT inhibition in FA plus TPA-treated cardiomyocytes reduced triacylglycerol but not diacylglycerol content, thus increasing the diacylglycerol/triacylglycerol ratio. In cardiomyocytes exposed to FA alone, GPAT inhibition reduced diacylglycerol but not triacylglycerol, thus decreasing the diacylglycerol/triacylglycerol ratio, prevented PKCδ activation and improved metabolic stress-stimulated glucose uptake. Changes in AMP-activated Protein Kinase activity failed to explain variations in metabolic stress-stimulated glucose uptake. Thus, LD formation regulates metabolic stress-stimulated glucose uptake in a manner best reflected by the diacylglycerol/triacylglycerol ratio.

DOI: https://doi.org/10.1038/s41598-023-42072-7
Cell Death Differ. 2023 Sep 07.

TRAP1 inhibits MARCH5-mediated MIC60 degradation to alleviate mitochondrial dysfunction and apoptosis of cardiomyocytes under diabetic conditions.

Lingxiao Zhang, Yuanyuan Luo, Linyan Lv, Siyong Chen, Guihua Liu, Tongfeng Zhao.

Mitochondrial dysfunction and cell death play important roles in diabetic cardiomyopathy, but the underlying mechanisms remain unclear. Here, we report that mitochondrial dysfunction and cell apoptosis are prominent features of primary cardiomyocytes after exposure to high glucose/palmitate conditions. The protein level of MIC60, a core component of mitochondrial cristae, is decreased via ubiquitination and degradation under these conditions. Exogenous expression of MIC60 alleviates cristae disruption, mitochondrial dysfunction and apoptosis. Moreover, we identified MARCH5 as an E3 ubiquitin ligase that specifically targets MIC60 in this process. Indeed, MARCH5 mediates K48-linked ubiquitination of MIC60 at Lys285 to promote its degradation. Mutation of the ubiquitination site in MIC60 or the MIC60-interacting motifs in MARCH5 abrogates MARCH5-mediated MIC60 ubiquitination and degradation. Silencing MARCH5 significantly alleviates high glucose/palmitate-induced mitochondrial dysfunction and apoptosis in primary cardiomyocytes. In addition to E3 ubiquitin ligases, molecular chaperones also play important roles in protein stability. We previously reported that the mitochondrial chaperone TRAP1 inhibits the ubiquitination of MIC60, but the detailed mechanism is unknown. Here, we find that TRAP1 performs this function by competing with MARCH5 for binding to MIC60. Our findings provide new insights into the mechanism underlying mitochondrial dysfunction in cardiomyocytes in diabetic cardiomyopathy. MARCH5 promotes ubiquitination of MIC60 to induce MIC60 degradation, mitochondrial dysfunction and apoptosis in cardiomyocytes under diabetic conditions. TRAP1 inhibits MARCH5-mediated ubiquitination by competitively interacting with MIC60.

DOI: https://doi.org/10.1038/s41418-023-01218-w