المؤلفون: Jing Zhu, Hui Xu, Yanhong Xue, Rakhilya Murtazina, Liangyi Chen, Wenjing Li, Rui Li, Yongheng Liang, Haiqian Xu, Liuju Li, Zhiping Xie, Juan Cai, Ao Zhang, Mengzhu Zhao, Xiaoshuai Huang, Qunli Li, Zulin Wu, Yi Ting Zhou, Xiaoxia Cong, Nava Segev, Valeriya Gyurkovska, Dan Sun, Fan Zhou, Lei Zhao

المصدر: Autophagy
The Journal of Cell Biology

مصطلحات موضوعية: Autophagosome, Saccharomyces cerevisiae Proteins, Endosome, Endocytic cycle, Autophagy-Related Proteins, Endosomes, Saccharomyces cerevisiae, macromolecular substances, Biology, Article, ESCRT, 03 medical and health sciences, 0302 clinical medicine, Lysosome, Autophagy, medicine, Research Articles, rab5 GTP-Binding Proteins, 030304 developmental biology, 0303 health sciences, Endosomal Sorting Complexes Required for Transport, Autophagosomes, Intracellular Membranes, Cell Biology, Transport protein, Cell biology, ESCRT complex, Protein Transport, medicine.anatomical_structure, Vacuoles, Commentary, Lysosomes, 030217 neurology & neurosurgery

الوصف: Zhou et al. identify the mechanism of autophagosome (AP) closure. They show that Rab5 GTPase regulates an interaction between the ESCRT subunit Snf7 and Atg17 to bring ESCRT to APs where it catalyzes AP closure. These findings highlight the convergence of the endocytic and autophagic pathways at this step.
In the conserved autophagy pathway, autophagosomes (APs) engulf cellular components and deliver them to the lysosome for degradation. Before fusing with the lysosome, APs have to close via an unknown mechanism. We have previously shown that the endocytic Rab5-GTPase regulates AP closure. Therefore, we asked whether ESCRT, which catalyzes scission of vesicles into late endosomes, mediates the topologically similar process of AP sealing. Here, we show that depletion of representative subunits from all ESCRT complexes causes late autophagy defects and accumulation of APs. Focusing on two subunits, we show that Snf7 and the Vps4 ATPase localize to APs and their depletion results in accumulation of open APs. Moreover, Snf7 and Vps4 proteins complement their corresponding mutant defects in vivo and in vitro. Finally, a Rab5-controlled Atg17–Snf7 interaction is important for Snf7 localization to APs. Thus, we unravel a mechanism in which a Rab5-dependent Atg17–Snf7 interaction leads to recruitment of ESCRT to open APs where ESCRT catalyzes AP closure.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::e4f388fa8467bed00c6cf9a8d6685d27Test
https://doi.org/10.1083/jcb.201811173Test

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

المؤلفون: Nava Segev, Zhanna Lipatova

المصدر: Cellular logistics. 4(3)

مصطلحات موضوعية: Endosome, Endocytic cycle, RAB1, Cell Biology, GTPase, Golgi apparatus, Biology, Biochemistry, Cell biology, Article Addendum, symbols.namesake, medicine.anatomical_structure, Lysosome, symbols, medicine, Molecular Medicine, Rab, Secretory pathway

الوصف: A prevailing question in the Ypt/Rab field is whether these conserved GTPases are specific to cellular compartments. The established role for Ypt1 and its human homolog Rab1 is in endoplasmic reticulum (ER)-to-Golgi transport. More recently these regulators were implicated also in autophagy. Two different TRAPP complexes, I and III, were identified as the guanine-nucleotide-exchange factors (GEFs) of Ypt1 in ER-to-Golgi transport and autophagy, respectively. Confusingly, Ypt1 and TRAPP III were also suggested to regulate endosome-to-Golgi transport, implying that they function at multiple cellular compartments, and bringing into question the nature of Ypt/Rab specificity. Recently, we showed that the role of TRAPP III and Ypt1 in autophagy occurs at the ER and that they do not regulate endosome-to-Golgi transport. Here, we discuss the significance of this conclusion to the idea that Ypt/Rabs are specific to cellular compartments. We postulate that Ypt1 regulates 2 alternative routes emanating from the ER toward the Golgi and the lysosome/vacuole. We further propose that the secretory and endocytic/lysosomal pathways intersect in 2 junctures, and 2 Ypts, Ypt1 and Ypt31, coordinate transport in the 2 intersections: Ypt1 links ER-to-Golgi and ER-to-autophagy transport, whereas Ypt31 links Golgi-to-plasma membrane (PM) transport with PM-to-Golgi recycling through endosomes.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::565f994a053d62693620c50428cf78a8Test
https://pubmed.ncbi.nlm.nih.gov/25610722Test