المؤلفون: Nava Segev

المصدر: PLoS Genetics, Vol 16, Iss 3, p e1008631 (2020)
PLoS Genetics

مصطلحات موضوعية: Cancer Research, Physiology, AMP-Activated Protein Kinases, QH426-470, Biochemistry, 0302 clinical medicine, Fluorescence Microscopy, AMP-activated protein kinase, Medicine and Health Sciences, Homeostasis, Proteasome endopeptidase complex, Genetics (clinical), 0303 health sciences, Microscopy, biology, Cell Death, Organic Compounds, Monosaccharides, Eukaryota, Light Microscopy, Cell biology, Chemistry, Immunoblot Analysis, medicine.anatomical_structure, Cell Processes, Physical Sciences, Cellular Structures and Organelles, Research Article, Proteasome Endopeptidase Complex, Autophagic Cell Death, Carbohydrates, Molecular Probe Techniques, Research and Analysis Methods, 03 medical and health sciences, Lysosome, medicine, Genetics, Microautophagy, Molecular Biology Techniques, Molecular Biology, Ecology, Evolution, Behavior and Systematics, 030304 developmental biology, Endosomal Sorting Complexes Required for Transport, Endoplasmic reticulum, Organic Chemistry, Chemical Compounds, Organisms, Fungi, Biology and Life Sciences, Proteins, Protein Complexes, Proteasomes, Cell Biology, Yeast, Glucose, Proteasome, Cytoplasm, Vacuoles, biology.protein, Lysosomes, Physiological Processes, 030217 neurology & neurosurgery

الوصف: The ubiquitin-proteasome system regulates numerous cellular processes and is central to protein homeostasis. In proliferating yeast and many mammalian cells, proteasomes are highly enriched in the nucleus. In carbon-starved yeast, proteasomes migrate to the cytoplasm and collect in proteasome storage granules (PSGs). PSGs dissolve and proteasomes return to the nucleus within minutes of glucose refeeding. The mechanisms by which cells regulate proteasome homeostasis under these conditions remain largely unknown. Here we show that AMP-activated protein kinase (AMPK) together with endosomal sorting complexes required for transport (ESCRTs) drive a glucose starvation-dependent microautophagy pathway that preferentially sorts aberrant proteasomes into the vacuole, thereby biasing accumulation of functional proteasomes in PSGs. The proteasome core particle (CP) and regulatory particle (RP) are regulated differently. Without AMPK, the insoluble protein deposit (IPOD) serves as an alternative site that specifically sequesters CP aggregates. Our findings reveal a novel AMPK-controlled ESCRT-mediated microautophagy mechanism in the regulation of proteasome trafficking and homeostasis under carbon starvation.
Author summary Protein homeostasis is critical for maintaining organismal health. The cellular dysfunction caused by accumulation and aggregation of aberrant proteins or other normally short-lived proteins is associated with aging and many human diseases, including neurodegenerative disorders, diabetes, and various types of cancer. The eukaryotic ubiquitin-proteasome system regulates numerous cellular processes and through selective protein degradation helps maintain cellular protein homeostasis under normal growth conditions. However, hundreds of cellular granules or condensates are formed during carbon starvation in yeast cells, including proteasome storage granules (PSGs). PSGs result from a massive relocation of proteasomes from the nucleus to the cytoplasm under these conditions. However, how cells regulate proteasome homeostasis under these conditions remains largely unknown. Here, we demonstrate that AMPK (AMP-activated protein kinase), a master cellular energy regulator, drives ESCRT (endosomal sorting complexes required for transport)-dependent microautophagy of aberrant proteasomes. This allows rapid re-mobilization of functional proteasomes from PSGs upon glucose refeeding. Previous studies had identified classical macroautophagy as a means of degrading proteasomes during starvation. Our work shows that direct uptake of proteasomes into the vacuole (lysosome) by microautophagy is a major means of proteasome elimination under limiting glucose conditions.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::3f7b24da07c39bca56371981d7aa4875Test
https://doaj.org/article/2a488a1e85c24a68be52664af1becbc9Test

المؤلفون: Yong Chen, Fan Zhou, Zulin Wu, Zhanna Lipatova, Weiming You, Zhiping Xie, Shenshen Zou, Xiaolong Zhu, Wenjing Li, Jie Cheng, Dan Sun, Nava Segev, Yongheng Liang, Yi Ting Zhou, Xiaoxia Cong, Yutao Liu, Qunli Li, Valeriya Gyurkovska, Rui Li

المصدر: PLoS Genetics, Vol 13, Iss 9, p e1007020 (2017)
PLoS Genetics

مصطلحات موضوعية: 0301 basic medicine, Autophagosome, Cancer Research, Hydrolases, Endocytic cycle, Autophagy-Related Proteins, GTPase, QH426-470, Biochemistry, Phosphatidylinositol 3-Kinases, Fluorescence Microscopy, Genetics (clinical), Microscopy, Cell Death, Kinase, Light Microscopy, Eukaryota, Proteases, Endocytosis, Cell biology, Enzymes, Protein Transport, medicine.anatomical_structure, Cell Processes, Cellular Structures and Organelles, Research Article, Saccharomyces cerevisiae Proteins, Endosome, Autophagic Cell Death, Endosomes, Saccharomyces cerevisiae, Biology, Research and Analysis Methods, 03 medical and health sciences, Lysosome, medicine, Autophagy, Genetics, Vesicles, Molecular Biology, Ecology, Evolution, Behavior and Systematics, rab5 GTP-Binding Proteins, Autophagosomes, Organisms, Fungi, Biology and Life Sciences, Proteins, Cell Biology, Yeast, Guanosine Triphosphatase, 030104 developmental biology, rab GTP-Binding Proteins, Vacuoles, Enzymology, Rab, Lysosomes

الوصف: In the conserved autophagy pathway, the double-membrane autophagosome (AP) engulfs cellular components to be delivered for degradation in the lysosome. While only sealed AP can productively fuse with the lysosome, the molecular mechanism of AP closure is currently unknown. Rab GTPases, which regulate all intracellular trafficking pathways in eukaryotes, also regulate autophagy. Rabs function in GTPase modules together with their activators and downstream effectors. In yeast, an autophagy-specific Ypt1 GTPase module, together with a set of autophagy-related proteins (Atgs) and a phosphatidylinositol-3-phosphate (PI3P) kinase, regulates AP formation. Fusion of APs and endosomes with the vacuole (the yeast lysosome) requires the Ypt7 GTPase module. We have previously shown that the Rab5-related Vps21, within its endocytic GTPase module, regulates autophagy. However, it was not clear which autophagy step it regulates. Here, we show that this module, which includes the Vps9 activator, the Rab5-related Vps21, the CORVET tethering complex, and the Pep12 SNARE, functions after AP expansion and before AP closure. Whereas APs are not formed in mutant cells depleted for Atgs, sealed APs accumulate in cells depleted for the Ypt7 GTPase module members. Importantly, depletion of individual members of the Vps21 module results in a novel phenotype: accumulation of unsealed APs. In addition, we show that Vps21-regulated AP closure precedes another AP maturation step, the previously reported PI3P phosphatase-dependent Atg dissociation. Our results delineate three successive steps in the autophagy pathway regulated by Rabs, Ypt1, Vps21 and Ypt7, and provide the first insight into the upstream regulation of AP closure.
Author summary In autophagy, a cellular recycling pathway, the double-membrane autophagosome (AP) engulfs excess or damaged cargo and delivers it for degradation in the lysosome for the reuse of its building blocks. While plenty of information is currently available regarding AP formation, expansion and fusion, not much is known about the regulation of AP closure, which is required for fusion of APs with the lysosome. Here, we use yeast genetics to characterize a novel mutant phenotype, accumulation of unsealed APs, and identify a role for the Rab5-related Vps21 GTPase in this process. Rab GTPases function in modules that include upstream activators and downstream effectors. We have previously shown that the same Vps21 module that regulates endocytosis also plays a role in autophagy. Using single and double mutant analyses, we find that this module is important for AP closure. Moreover, we delineate three Rab GTPase-regulated steps in the autophagy pathway: AP formation, closure, and fusion, which are regulated by Ypt1, Vps21 and Ypt7, respectively. This study provides the first insight into the mechanism of the elusive process of AP closure.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::d0bef356536ed628bba11d5dba899c51Test
https://doaj.org/article/c18c3b7a623e42bba1a6abfa803f5825Test