1
|
Janusz-Kaminska A, Brzozowska A, Tempes A, Urbanska M, Blazejczyk M, Miłek J, Kuzniewska B, Zeng J, Wesławski J, Kisielewska K, Bassell GJ, Jaworski J. Rab11 regulates autophagy at dendritic spines in an mTOR- and NMDA-dependent manner. Mol Biol Cell 2024; 35:ar43. [PMID: 38294869 PMCID: PMC10916872 DOI: 10.1091/mbc.e23-02-0060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Revised: 11/30/2023] [Accepted: 01/22/2024] [Indexed: 02/01/2024] Open
Abstract
Synaptic plasticity is a process that shapes neuronal connections during neurodevelopment and learning and memory. Autophagy is a mechanism that allows the cell to degrade its unnecessary or dysfunctional components. Autophagosomes appear at dendritic spines in response to plasticity-inducing stimuli. Autophagy defects contribute to altered dendritic spine development, autistic-like behavior in mice, and neurological disease. While several studies have explored the involvement of autophagy in synaptic plasticity, the initial steps of the emergence of autophagosomes at the postsynapse remain unknown. Here, we demonstrate a postsynaptic association of autophagy-related protein 9A (Atg9A), known to be involved in the early stages of autophagosome formation, with Rab11, a small GTPase that regulates endosomal trafficking. Rab11 activity was necessary to maintain Atg9A-positive structures at dendritic spines. Inhibition of mTOR increased Rab11 and Atg9A interaction and increased the emergence of LC3 positive vesicles, an autophagosome membrane-associated protein marker, in dendritic spines when coupled to NMDA receptor stimulation. Dendritic spines with newly formed LC3+ vesicles were more resistant to NMDA-induced morphologic change. Rab11 DN overexpression suppressed appearance of LC3+ vesicles. Collectively, these results suggest that initiation of autophagy in dendritic spines depends on neuronal activity and Rab11a-dependent Atg9A interaction that is regulated by mTOR activity.
Collapse
Affiliation(s)
- Aleksandra Janusz-Kaminska
- Laboratory of Molecular and Cellular Neurobiology, International Institute of Molecular and Cell Biology, 02-109 Warszawa, Poland
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322
| | - Agnieszka Brzozowska
- Laboratory of Molecular and Cellular Neurobiology, International Institute of Molecular and Cell Biology, 02-109 Warszawa, Poland
| | - Aleksandra Tempes
- Laboratory of Molecular and Cellular Neurobiology, International Institute of Molecular and Cell Biology, 02-109 Warszawa, Poland
| | - Malgorzata Urbanska
- Laboratory of Molecular and Cellular Neurobiology, International Institute of Molecular and Cell Biology, 02-109 Warszawa, Poland
| | - Magdalena Blazejczyk
- Laboratory of Molecular and Cellular Neurobiology, International Institute of Molecular and Cell Biology, 02-109 Warszawa, Poland
| | - Jacek Miłek
- Laboratory of Molecular Basis of Synaptic Plasticity, Centre of New Technologies, University of Warsaw, 02-097 Warsaw, Poland
| | - Bozena Kuzniewska
- Laboratory of Molecular Basis of Synaptic Plasticity, Centre of New Technologies, University of Warsaw, 02-097 Warsaw, Poland
| | - Juan Zeng
- Laboratory of Molecular and Cellular Neurobiology, International Institute of Molecular and Cell Biology, 02-109 Warszawa, Poland
| | - Jan Wesławski
- Laboratory of Molecular and Cellular Neurobiology, International Institute of Molecular and Cell Biology, 02-109 Warszawa, Poland
| | - Katarzyna Kisielewska
- Laboratory of Molecular and Cellular Neurobiology, International Institute of Molecular and Cell Biology, 02-109 Warszawa, Poland
| | - Gary J. Bassell
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322
| | - Jacek Jaworski
- Laboratory of Molecular and Cellular Neurobiology, International Institute of Molecular and Cell Biology, 02-109 Warszawa, Poland
| |
Collapse
|
2
|
Arlt H, Raman B, Filali-Mouncef Y, Hu Y, Leytens A, Hardenberg R, Guimarães R, Kriegenburg F, Mari M, Smaczynska-de Rooij II, Ayscough KR, Dengjel J, Ungermann C, Reggiori F. The dynamin Vps1 mediates Atg9 transport to the sites of autophagosome formation. J Biol Chem 2023; 299:104712. [PMID: 37060997 DOI: 10.1016/j.jbc.2023.104712] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Revised: 03/14/2023] [Accepted: 04/06/2023] [Indexed: 04/17/2023] Open
Abstract
Autophagy is a key process in eukaryotes to maintain cellular homeostasis by delivering cellular components to lysosomes/vacuoles for degradation and reuse of the resulting metabolites. Membrane rearrangements and trafficking events are mediated by the core machinery of autophagy-related (Atg) proteins, which carry out a variety of functions. How Atg9, a lipid scramblase and the only conserved transmembrane protein within this core Atg machinery, is trafficked during autophagy remained largely unclear. Here, we addressed this question in yeast Saccharomyces cerevisiae and found that retromer complex and dynamin Vps1 mutants alter Atg9 subcellular distribution and severely impair the autophagic flux by affecting two separate autophagy steps. We provide evidence that Vps1 interacts with Atg9 at Atg9 reservoirs. In the absence of Vps1, Atg9 fails to reach the sites of autophagosome formation, and this results in an autophagy defect. The function of Vps1 in autophagy requires its GTPase activity. Moreover, Vps1 point mutants associated with human diseases such as microcytic anemia and Charcot-Marie-Tooth are unable to sustain autophagy and affect Atg9 trafficking. Together, our data provide novel insights on the role of dynamins in Atg9 trafficking and suggest that a defect in this autophagy step could contribute to severe human pathologies.
Collapse
Affiliation(s)
- Henning Arlt
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands; University of Osnabrück, Department of Biology/Chemistry, Biochemistry section, Barbarastrasse 13, 49076 Osnabrück, Germany
| | - Babu Raman
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Yasmina Filali-Mouncef
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Yan Hu
- Department of Biomedicine, Aarhus University, Ole Worms Allé 4, 8000 Aarhus C, Denmark
| | - Alexandre Leytens
- Department of Biology, University of Fribourg, 1700 Fribourg, Switzerland
| | - Ralph Hardenberg
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Rodrigo Guimarães
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Franziska Kriegenburg
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Muriel Mari
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands; Department of Biomedicine, Aarhus University, Ole Worms Allé 4, 8000 Aarhus C, Denmark
| | | | - Kathryn R Ayscough
- Department of Biomedical Sciences, University of Sheffield, Sheffield, S10 2TN, United Kingdom
| | - Jörn Dengjel
- Department of Biology, University of Fribourg, 1700 Fribourg, Switzerland
| | - Christian Ungermann
- University of Osnabrück, Department of Biology/Chemistry, Biochemistry section, Barbarastrasse 13, 49076 Osnabrück, Germany
| | - Fulvio Reggiori
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands; Department of Biomedicine, Aarhus University, Ole Worms Allé 4, 8000 Aarhus C, Denmark; Aarhus Institute of Advanced Studies (AIAS), Aarhus University, Høegh-Guldbergs Gade 6B, 8000 Aarhus C, Denmark.
| |
Collapse
|
3
|
Gao A, Zou J, Mao Z, Zhou H, Zeng G. SUMO2-mediated SUMOylation of SH3GLB1 promotes ionizing radiation-induced hypertrophic cardiomyopathy through mitophagy activation. Eur J Pharmacol 2022; 924:174980. [PMID: 35487252 DOI: 10.1016/j.ejphar.2022.174980] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Revised: 04/05/2022] [Accepted: 04/22/2022] [Indexed: 12/25/2022]
Abstract
Hypertrophic cardiomyopathy (HC) is characterized by the enlargement of individual cardiomyocytes, which is a typical pathophysiological process that occurs in various cardiovascular diseases. Ionizing radiation (IR) is an important independent risk factor for hypertrophic cardiomyopathy, but the underlying molecular mechanism is still unclear. In the present study, we aimed to clarify the role of IR in promoting cardiac hypertrophy and investigate the mechanism by which the SUMO2-mediated SUMOylation of SH3GLB1 affects mitophagy in IR-induced cardiac hypertrophy. In vivo, IR promoted cardiac hypertrophy by activating mitophagy. In vitro, IR upregulated PINK1 and Parkin protein expression and damaged mitochondrial morphological structure. We further demonstrated that SH3GLB1 deficiency inhibited mitophagy activation and restored mitochondrial cristae, revealing a regulatory role of SH3GLB1 in cardiac hypertrophy. IR promoted interactions between SH3GLB1 and mitochondrial membrane proteins, such as MFN1/2, TOM20 and Drp1, further indicating that the mechanism by which SH3GLB1 functions in cardiac hypertrophy might involve mitophagy. A bioinformatics prediction found that SUMO2 could SUMOylate SH3GLB1 at position K82. Consistent with this finding, both co-IP assays and laser confocal microscopy showed that IR promoted the interaction and colocalization of SUMO2 and SH3GLB1. In summary, our study identifies IR as an important factor that promotes hypertrophic cardiomyopathy by accelerating the activation of mitophagy through the SUMO2-mediated SUMOylation of SH3GLB1; thus, IR exerts dual therapeutic effects in the treatment of thoracic tumours with long-term radiotherapy. Additionally, this study provides novel treatment strategies and targets for preventing the hypertrophic cardiomyopathy caused by thoracic tumour radiotherapy. Furthermore, SH3GLB1 may be a promising experimental target for the development of strategies for treating cardiovascular diseases caused by IR.
Collapse
Affiliation(s)
- Anbo Gao
- Clinical Research Institute, The Second Affiliated Hospital, Hengyang Medical School, University of South China, Hengyang, 421002, Hunan, China; Department of Cardiovascular Medicine, The Second Affiliated Hospital, Hengyang Medical School, University of South China, Key Laboratory of Heart Failure Prevention & Treatment of Hengyang, Clinical Medicine Research Center of Arteriosclerotic Disease of Hunan Province, Hengyang, 421002, Hunan, China
| | - Jin Zou
- Department of Cardiovascular Medicine, The First Affiliated Hospital, Hengyang Medical School, University of South China, Hengyang, 421002, Hunan, China
| | - Zhenjiang Mao
- Department of Gastroenterology, The Second Affiliated Hospital, Hengyang Medical School, University of South China, Hengyang, 421002, Hunan, China
| | - Hong Zhou
- Department of Radiology, The First Affiliated Hospital, Hengyang Medical School, University of South China, Hengyang, 421002, Hunan, China.
| | - Gaofeng Zeng
- Department of Cardiovascular Medicine, The Second Affiliated Hospital, Hengyang Medical School, University of South China, Key Laboratory of Heart Failure Prevention & Treatment of Hengyang, Clinical Medicine Research Center of Arteriosclerotic Disease of Hunan Province, Hengyang, 421002, Hunan, China.
| |
Collapse
|
4
|
Campisi D, Desrues L, Dembélé KP, Mutel A, Parment R, Gandolfo P, Castel H, Morin F. The core autophagy protein ATG9A controls dynamics of cell protrusions and directed migration. J Cell Biol 2022; 221:e202106014. [PMID: 35180289 PMCID: PMC8932524 DOI: 10.1083/jcb.202106014] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Revised: 11/09/2021] [Accepted: 12/08/2021] [Indexed: 01/18/2023] Open
Abstract
Chemotactic migration is a fundamental cellular behavior relying on the coordinated flux of lipids and cargo proteins toward the leading edge. We found here that the core autophagy protein ATG9A plays a critical role in the chemotactic migration of several human cell lines, including highly invasive glioma cells. Depletion of ATG9A protein altered the formation of large and persistent filamentous actin (F-actin)-rich lamellipodia that normally drive directional migration. Using live-cell TIRF microscopy, we demonstrated that ATG9A-positive vesicles are targeted toward the migration front of polarized cells, where their exocytosis correlates with protrusive activity. Finally, we found that ATG9A was critical for efficient delivery of β1 integrin to the leading edge and normal adhesion dynamics. Collectively, our data uncover a new function for ATG9A protein and indicate that ATG9A-positive vesicles are mobilized during chemotactic stimulation to facilitate expansion of the lamellipodium and its anchorage to the extracellular matrix.
Collapse
Affiliation(s)
- Daniele Campisi
- Normandie University, UNIROUEN, Institut national de la santé et de la recherche médicale U1239, DC2N, Rouen, France
- Institute for Research and Innovation in Biomedicine, Rouen, France
| | - Laurence Desrues
- Normandie University, UNIROUEN, Institut national de la santé et de la recherche médicale U1239, DC2N, Rouen, France
- Institute for Research and Innovation in Biomedicine, Rouen, France
| | - Kléouforo-Paul Dembélé
- Normandie University, UNIROUEN, Institut national de la santé et de la recherche médicale U1239, DC2N, Rouen, France
- Institute for Research and Innovation in Biomedicine, Rouen, France
| | - Alexandre Mutel
- Normandie University, UNIROUEN, Institut national de la santé et de la recherche médicale U1239, DC2N, Rouen, France
- Institute for Research and Innovation in Biomedicine, Rouen, France
| | - Renaud Parment
- Normandie University, UNIROUEN, Institut national de la santé et de la recherche médicale U1239, DC2N, Rouen, France
- Institute for Research and Innovation in Biomedicine, Rouen, France
| | - Pierrick Gandolfo
- Normandie University, UNIROUEN, Institut national de la santé et de la recherche médicale U1239, DC2N, Rouen, France
- Institute for Research and Innovation in Biomedicine, Rouen, France
| | - Hélène Castel
- Normandie University, UNIROUEN, Institut national de la santé et de la recherche médicale U1239, DC2N, Rouen, France
- Institute for Research and Innovation in Biomedicine, Rouen, France
| | - Fabrice Morin
- Normandie University, UNIROUEN, Institut national de la santé et de la recherche médicale U1239, DC2N, Rouen, France
- Institute for Research and Innovation in Biomedicine, Rouen, France
| |
Collapse
|
5
|
Kannangara AR, Poole DM, McEwan CM, Youngs JC, Weerasekara VK, Thornock AM, Lazaro MT, Balasooriya ER, Oh LM, Soderblom EJ, Lee JJ, Simmons DL, Andersen JL. BioID reveals an ATG9A interaction with ATG13-ATG101 in the degradation of p62/SQSTM1-ubiquitin clusters. EMBO Rep 2021; 22:e51136. [PMID: 34369648 DOI: 10.15252/embr.202051136] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 07/14/2021] [Accepted: 07/16/2021] [Indexed: 01/13/2023] Open
Abstract
ATG9A, the only multi-pass transmembrane protein among core ATG proteins, is an essential regulator of autophagy, yet its regulatory mechanisms and network of interactions are poorly understood. Through quantitative BioID proteomics, we identify a network of ATG9A interactions that includes members of the ULK1 complex and regulators of membrane fusion and vesicle trafficking, including the TRAPP, EARP, GARP, exocyst, AP-1, and AP-4 complexes. These interactions mark pathways of ATG9A trafficking through ER, Golgi, and endosomal systems. In exploring these data, we find that ATG9A interacts with components of the ULK1 complex, particularly ATG13 and ATG101. Using knockout/reconstitution and split-mVenus approaches to capture the ATG13-ATG101 dimer, we find that ATG9A interacts with ATG13-ATG101 independently of ULK1. Deletion of ATG13 or ATG101 causes a shift in ATG9A distribution, resulting in an aberrant accumulation of ATG9A at stalled clusters of p62/SQSTM1 and ubiquitin, which can be rescued by an ULK1 binding-deficient mutant of ATG13. Together, these data reveal ATG9A interactions in vesicle-trafficking and autophagy pathways, including a role for an ULK1-independent ATG13 complex in regulating ATG9A.
Collapse
Affiliation(s)
- Ashari R Kannangara
- Department of Chemistry and Biochemistry, Fritz B. Burns Cancer Research Laboratory, Brigham Young University, Provo, UT, USA
| | - Daniel M Poole
- Department of Chemistry and Biochemistry, Fritz B. Burns Cancer Research Laboratory, Brigham Young University, Provo, UT, USA
| | - Colten M McEwan
- Department of Chemistry and Biochemistry, Fritz B. Burns Cancer Research Laboratory, Brigham Young University, Provo, UT, USA
| | - Joshua C Youngs
- Department of Chemistry and Biochemistry, Fritz B. Burns Cancer Research Laboratory, Brigham Young University, Provo, UT, USA
| | - Vajira K Weerasekara
- Center for Cancer Research, Massachusetts General Hospital, Boston, MA, USA.,Department of Medicine, Harvard Medical School, Boston, MA, USA
| | - Alex M Thornock
- Department of Chemistry and Biochemistry, Fritz B. Burns Cancer Research Laboratory, Brigham Young University, Provo, UT, USA
| | - Misael T Lazaro
- Department of Chemistry and Biochemistry, Fritz B. Burns Cancer Research Laboratory, Brigham Young University, Provo, UT, USA
| | - Eranga R Balasooriya
- Department of Chemistry and Biochemistry, Fritz B. Burns Cancer Research Laboratory, Brigham Young University, Provo, UT, USA
| | - Laura M Oh
- Department of Chemistry and Biochemistry, Fritz B. Burns Cancer Research Laboratory, Brigham Young University, Provo, UT, USA
| | - Erik J Soderblom
- Proteomics and Metabolomics Shared Resource, Duke University School of Medicine, Durham, NC, USA
| | - Jonathan J Lee
- Department of Chemistry and Biochemistry, Fritz B. Burns Cancer Research Laboratory, Brigham Young University, Provo, UT, USA
| | - Daniel L Simmons
- Department of Chemistry and Biochemistry, Fritz B. Burns Cancer Research Laboratory, Brigham Young University, Provo, UT, USA
| | - Joshua L Andersen
- Department of Chemistry and Biochemistry, Fritz B. Burns Cancer Research Laboratory, Brigham Young University, Provo, UT, USA
| |
Collapse
|
6
|
Barz S, Kriegenburg F, Sánchez-Martín P, Kraft C. Small but mighty: Atg8s and Rabs in membrane dynamics during autophagy. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2021; 1868:119064. [PMID: 34048862 PMCID: PMC8261831 DOI: 10.1016/j.bbamcr.2021.119064] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Figures] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Revised: 05/04/2021] [Accepted: 05/21/2021] [Indexed: 11/17/2022]
Abstract
Autophagy is a degradative pathway during which autophagosomes are formed that enwrap cytosolic material destined for turnover within the lytic compartment. Autophagosome biogenesis requires controlled lipid and membrane rearrangements to allow the formation of an autophagosomal seed and its subsequent elongation into a fully closed and fusion-competent double membrane vesicle. Different membrane remodeling events are required, which are orchestrated by the distinct autophagy machinery. An important player among these autophagy proteins is the small lipid-modifier Atg8. Atg8 proteins facilitate various aspects of autophagosome formation and serve as a binding platform for autophagy factors. Also Rab GTPases have been implicated in autophagosome biogenesis. As Atg8 proteins interact with several Rab GTPase regulators, they provide a possible link between autophagy progression and Rab GTPase activity. Here, we review central aspects in membrane dynamics during autophagosome biogenesis with a focus on Atg8 proteins and selected Rab GTPases.
Collapse
Affiliation(s)
- Saskia Barz
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany; Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany; Spemann Graduate School of Biology and Medicine (SGBM), University of Freiburg, 79104 Freiburg, Germany
| | - Franziska Kriegenburg
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - Pablo Sánchez-Martín
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - Claudine Kraft
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany; CIBSS - Centre for Integrative Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany.
| |
Collapse
|
7
|
Gómez-Sánchez R, Tooze SA, Reggiori F. Membrane supply and remodeling during autophagosome biogenesis. Curr Opin Cell Biol 2021; 71:112-119. [PMID: 33930785 DOI: 10.1016/j.ceb.2021.02.001] [Citation(s) in RCA: 48] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 01/17/2021] [Accepted: 02/04/2021] [Indexed: 12/17/2022]
Abstract
The de novo generation of double-membrane autophagosomes is the hallmark of autophagy. The initial membranous precursor cisterna, the phagophore, is very likely generated by the fusion of vesicles and acts as a membrane seed for the subsequent expansion into an autophagosome. This latter step requires a massive convoy of lipids into the phagophore. In this review, we present recent advances in our understanding of the intracellular membrane sources and lipid delivery mechanisms, which principally rely on vesicular transport and membrane contact sites that contribute to autophagosome biogenesis. In this context, we discuss lipid biosynthesis and lipid remodeling events that play a crucial role in both phagophore nucleation and expansion.
Collapse
Affiliation(s)
- Rubén Gómez-Sánchez
- Department of Biomedical Sciences of Cells & Systems, University of Groningen, University Medical Center Groningen, A. Deusinglaan 1, 9713 AV Groningen, the Netherlands
| | - Sharon A Tooze
- Molecular Cell Biology of Autophagy, The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, United Kingdom
| | - Fulvio Reggiori
- Department of Biomedical Sciences of Cells & Systems, University of Groningen, University Medical Center Groningen, A. Deusinglaan 1, 9713 AV Groningen, the Netherlands.
| |
Collapse
|
8
|
TOM40 Targets Atg2 to Mitochondria-Associated ER Membranes for Phagophore Expansion. Cell Rep 2020; 28:1744-1757.e5. [PMID: 31412244 PMCID: PMC6701867 DOI: 10.1016/j.celrep.2019.07.036] [Citation(s) in RCA: 70] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2019] [Revised: 06/03/2019] [Accepted: 07/12/2019] [Indexed: 12/20/2022] Open
Abstract
During autophagy, phagophores grow into doublemembrane vesicles called autophagosomes, but the underlying mechanism remains unclear. Here, we show a critical role of Atg2A in phagophore expansion. Atg2A translocates to the phagophore at the mitochondria-associated ER membrane (MAM) through a C-terminal 45-amino acid domain that we have termed the MAM localization domain (MLD). Proteomic analysis identifies the outer mitochondrial membrane protein TOM40 as a MLD-interacting partner. The Atg2A-TOM40 interaction is responsible for MAM localization of Atg2A and requires the TOM receptor protein TOM70. In addition, Atg2A interacts with Atg9A by a region within its N terminus. Inhibition of either Atg2A-TOM40 or Atg2A-Atg9A interactions impairs phagophore expansion and accumulates Atg9A-vesicles in the vicinity of autophagic structures. Collectively, we propose a model that the TOM70-TOM40 complex recruits Atg2A to the MAM for vesicular and/or nonvesicular lipid transport into the expanding phagophore to grow the size of autophagosomes for efficient autophagic flux. Tang et al. show that human Atg2 is a key regulator for phagophore expansion. TOM40/70 directs Atg2A to MAM to mediate phagophore expansion. On the MAM, Atg2A facilitates Atg9-vesicle delivery and retrograde trafficking to promote phagophore expansion and efficient autophagic flux.
Collapse
|
9
|
De Tito S, Hervás JH, van Vliet AR, Tooze SA. The Golgi as an Assembly Line to the Autophagosome. Trends Biochem Sci 2020; 45:484-496. [PMID: 32307224 DOI: 10.1016/j.tibs.2020.03.010] [Citation(s) in RCA: 59] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 03/05/2020] [Accepted: 03/17/2020] [Indexed: 12/11/2022]
Abstract
Autophagy is traditionally depicted as a signaling cascade that culminates in the formation of an autophagosome that degrades cellular cargo. However, recent studies have identified myriad pathways and cellular organelles underlying the autophagy process, be it as signaling platforms or through the contribution of proteins and lipids. The Golgi complex is recognized as being a central transport hub in the cell, with a critical role in endocytic trafficking and endoplasmic reticulum (ER) to plasma membrane (PM) transport. However, the Golgi is also an important site of key autophagy regulators, including the protein autophagy-related (ATG)-9A and the lipid, phosphatidylinositol-4-phosphate [PI(4)P]. In this review, we highlight the central function of this organelle in autophagy as a transport hub supplying various components of autophagosome formation.
Collapse
Affiliation(s)
- Stefano De Tito
- The Molecular Cell Biology of Autophagy, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Javier H Hervás
- The Molecular Cell Biology of Autophagy, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK; Instituto Biofisika (CSIC, UPV/EHU), Departamento de Bioquímica y Biología Molecular, Universidad del País Vasco, Bilbao, Spain
| | - Alexander R van Vliet
- The Molecular Cell Biology of Autophagy, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Sharon A Tooze
- The Molecular Cell Biology of Autophagy, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK.
| |
Collapse
|
10
|
Emerging roles of ATG proteins and membrane lipids in autophagosome formation. Cell Discov 2020; 6:32. [PMID: 32509328 PMCID: PMC7248066 DOI: 10.1038/s41421-020-0161-3] [Citation(s) in RCA: 153] [Impact Index Per Article: 38.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Accepted: 03/21/2020] [Indexed: 12/12/2022] Open
Abstract
Autophagosome biogenesis is a dynamic membrane event, which is executed by the sequential function of autophagy-related (ATG) proteins. Upon autophagy induction, a cup-shaped membrane structure appears in the cytoplasm, then elongates sequestering cytoplasmic materials, and finally forms a closed double membrane autophagosome. However, how this complex vesicle formation event is strictly controlled and achieved is still enigmatic. Recently, there is accumulating evidence showing that some ATG proteins have the ability to directly interact with membranes, transfer lipids between membranes and regulate lipid metabolism. A novel role for various membrane lipids in autophagosome formation is also emerging. Here, we highlight past and recent key findings on the function of ATG proteins related to autophagosome biogenesis and consider how ATG proteins control this dynamic membrane formation event to organize the autophagosome by collaborating with membrane lipids.
Collapse
|
11
|
Birgisdottir ÅB, Johansen T. Autophagy and endocytosis – interconnections and interdependencies. J Cell Sci 2020; 133:133/10/jcs228114. [DOI: 10.1242/jcs.228114] [Citation(s) in RCA: 52] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
ABSTRACT
Autophagy and endocytosis are membrane-vesicle-based cellular pathways for degradation and recycling of intracellular and extracellular components, respectively. These pathways have a common endpoint at the lysosome, where their cargo is degraded. In addition, the two pathways intersect at different stages during vesicle formation, fusion and trafficking, and share parts of the molecular machinery. Accumulating evidence shows that autophagy is dependent upon endocytosis and vice versa. The emerging joint network of autophagy and endocytosis is of vital importance for cellular metabolism and signaling, and thus also highly relevant in disease settings. In this Review, we will discuss examples of how the autophagy machinery impacts on endocytosis and cell signaling, and highlight how endocytosis regulates the different steps in autophagy in mammalian cells. Finally, we will focus on the interplay of these pathways in the quality control of their common endpoint, the lysosome.
Collapse
Affiliation(s)
- Åsa B. Birgisdottir
- The Heart and Lung Clinic, University Hospital of North Norway, 9037 Tromsø, Norway
- Clinical Cardiovascular Research Group, Department of Clinical Medicine, University of Tromsø –The Arctic University of Norway, 9037 Tromsø, Norway
| | - Terje Johansen
- Molecular Cancer Research Group, Department of Medical Biology, University of Tromsø–The Arctic University of Norway, 9037 Tromsø, Norway
| |
Collapse
|
12
|
Besemer AS, Maus J, Ax MDA, Stein A, Vo S, Freese C, Nalbach K, von Hilchen C, Pfalzgraf IF, Koziollek-Drechsler I, Silva B, Huesmann H, Boukhallouk F, Florin L, Kern A, Behl C, Clement AM. Receptor-mediated endocytosis 8 (RME-8)/DNAJC13 is a novel positive modulator of autophagy and stabilizes cellular protein homeostasis. Cell Mol Life Sci 2020; 78:645-660. [PMID: 32322926 PMCID: PMC7873018 DOI: 10.1007/s00018-020-03521-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Revised: 03/20/2020] [Accepted: 04/06/2020] [Indexed: 12/15/2022]
Abstract
The cellular protein homeostasis (proteostasis) network responds effectively to insults. In a functional screen in C. elegans, we recently identified the gene receptor-mediated endocytosis 8 (rme-8; human ortholog: DNAJC13) as a component of the proteostasis network. Accumulation of aggregation-prone proteins, such as amyloid-β 42 (Aβ), α-synuclein, or mutant Cu/Zn-superoxide dismutase (SOD1), were aggravated upon the knockdown of rme-8/DNAJC13 in C. elegans and in human cell lines, respectively. DNAJC13 is involved in endosomal protein trafficking and associated with the retromer and the WASH complex. As both complexes have been linked to autophagy, we investigated the role of DNAJC13 in this degradative pathway. In knockdown and overexpression experiments, DNAJC13 acts as a positive modulator of autophagy. In contrast, the overexpression of the Parkinson’s disease-associated mutant DNAJC13(N855S) did not enhance autophagy. Reduced DNAJC13 levels affected ATG9A localization at and its transport from the recycling endosome. As a consequence, ATG9A co-localization at LC3B-positive puncta under steady-state and autophagy-induced conditions is impaired. These data demonstrate a novel function of RME-8/DNAJC13 in cellular homeostasis by modulating ATG9A trafficking and autophagy.
Collapse
Affiliation(s)
- Anna S Besemer
- Institute of Pathobiochemistry, University Medical Center of the Johannes Gutenberg-University, Duesbergweg 6, 55128, Mainz, Germany
| | - Joanna Maus
- Institute of Pathobiochemistry, University Medical Center of the Johannes Gutenberg-University, Duesbergweg 6, 55128, Mainz, Germany
| | - Mirjam D A Ax
- Institute of Pathobiochemistry, University Medical Center of the Johannes Gutenberg-University, Duesbergweg 6, 55128, Mainz, Germany
| | - Anna Stein
- Institute of Pathobiochemistry, University Medical Center of the Johannes Gutenberg-University, Duesbergweg 6, 55128, Mainz, Germany
| | - Stella Vo
- Institute of Pathobiochemistry, University Medical Center of the Johannes Gutenberg-University, Duesbergweg 6, 55128, Mainz, Germany
| | - Christian Freese
- Institute of Pathobiochemistry, University Medical Center of the Johannes Gutenberg-University, Duesbergweg 6, 55128, Mainz, Germany
| | - Karsten Nalbach
- Institute of Pathobiochemistry, University Medical Center of the Johannes Gutenberg-University, Duesbergweg 6, 55128, Mainz, Germany
| | - Christian von Hilchen
- Institute of Pathobiochemistry, University Medical Center of the Johannes Gutenberg-University, Duesbergweg 6, 55128, Mainz, Germany
| | - Ines F Pfalzgraf
- Institute of Pathobiochemistry, University Medical Center of the Johannes Gutenberg-University, Duesbergweg 6, 55128, Mainz, Germany
| | - Ingrid Koziollek-Drechsler
- Institute of Pathobiochemistry, University Medical Center of the Johannes Gutenberg-University, Duesbergweg 6, 55128, Mainz, Germany
| | - Beate Silva
- Institute of Pathobiochemistry, University Medical Center of the Johannes Gutenberg-University, Duesbergweg 6, 55128, Mainz, Germany
| | - Heike Huesmann
- Institute of Pathobiochemistry, University Medical Center of the Johannes Gutenberg-University, Duesbergweg 6, 55128, Mainz, Germany
| | - Fatima Boukhallouk
- Institute of Medical Microbiology and Hygiene, University Medical Center of the Johannes Gutenberg-University, 55101 Mainz, Germany
| | - Luise Florin
- Institute for Virology and Research Center for Immunotherapy (FZI), University Medical Center of the Johannes Gutenberg-University, 55101 Mainz, Germany
| | - Andreas Kern
- Institute of Pathobiochemistry, University Medical Center of the Johannes Gutenberg-University, Duesbergweg 6, 55128, Mainz, Germany
| | - Christian Behl
- Institute of Pathobiochemistry, University Medical Center of the Johannes Gutenberg-University, Duesbergweg 6, 55128, Mainz, Germany.
| | - Albrecht M Clement
- Institute of Pathobiochemistry, University Medical Center of the Johannes Gutenberg-University, Duesbergweg 6, 55128, Mainz, Germany.
| |
Collapse
|
13
|
Zhukovsky MA, Filograna A, Luini A, Corda D, Valente C. Protein Amphipathic Helix Insertion: A Mechanism to Induce Membrane Fission. Front Cell Dev Biol 2019; 7:291. [PMID: 31921835 PMCID: PMC6914677 DOI: 10.3389/fcell.2019.00291] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Accepted: 11/06/2019] [Indexed: 12/19/2022] Open
Abstract
One of the fundamental features of biomembranes is the ability to fuse or to separate. These processes called respectively membrane fusion and fission are central in the homeostasis of events such as those related to intracellular membrane traffic. Proteins that contain amphipathic helices (AHs) were suggested to mediate membrane fission via shallow insertion of these helices into the lipid bilayer. Here we analyze the AH-containing proteins that have been identified as essential for membrane fission and categorize them in few subfamilies, including small GTPases, Atg proteins, and proteins containing either the ENTH/ANTH- or the BAR-domain. AH-containing fission-inducing proteins may require cofactors such as additional proteins (e.g., lipid-modifying enzymes), or lipids (e.g., phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2], phosphatidic acid [PA], or cardiolipin). Both PA and cardiolipin possess a cone shape and a negative charge (-2) that favor the recruitment of the AHs of fission-inducing proteins. Instead, PtdIns(4,5)P2 is characterized by an high negative charge able to recruit basic residues of the AHs of fission-inducing proteins. Here we propose that the AHs of fission-inducing proteins contain sequence motifs that bind lipid cofactors; accordingly (K/R/H)(K/R/H)xx(K/R/H) is a PtdIns(4,5)P2-binding motif, (K/R)x6(F/Y) is a cardiolipin-binding motif, whereas KxK is a PA-binding motif. Following our analysis, we show that the AHs of many fission-inducing proteins possess five properties: (a) at least three basic residues on the hydrophilic side, (b) ability to oligomerize, (c) optimal (shallow) depth of insertion into the membrane, (d) positive cooperativity in membrane curvature generation, and (e) specific interaction with one of the lipids mentioned above. These lipid cofactors favor correct conformation, oligomeric state and optimal insertion depth. The most abundant lipid in a given organelle possessing high negative charge (more negative than -1) is usually the lipid cofactor in the fission event. Interestingly, naturally occurring mutations have been reported in AH-containing fission-inducing proteins and related to diseases such as centronuclear myopathy (amphiphysin 2), Charcot-Marie-Tooth disease (GDAP1), Parkinson's disease (α-synuclein). These findings add to the interest of the membrane fission process whose complete understanding will be instrumental for the elucidation of the pathogenesis of diseases involving mutations in the protein AHs.
Collapse
Affiliation(s)
- Mikhail A. Zhukovsky
- Institute of Biochemistry and Cell Biology, National Research Council, Naples, Italy
| | | | | | - Daniela Corda
- Institute of Biochemistry and Cell Biology, National Research Council, Naples, Italy
| | - Carmen Valente
- Institute of Biochemistry and Cell Biology, National Research Council, Naples, Italy
| |
Collapse
|
14
|
Staiano L, Zappa F. Hijacking intracellular membranes to feed autophagosomal growth. FEBS Lett 2019; 593:3120-3134. [PMID: 31603532 DOI: 10.1002/1873-3468.13637] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Revised: 10/02/2019] [Accepted: 10/03/2019] [Indexed: 12/21/2022]
Abstract
Autophagy is widely considered as a housekeeping mechanism that enables cells to survive stress conditions and, in particular, nutrient deprivation. Autophagy begins with the formation of the phagophore that expands and closes around cytosolic material and damaged organelles destined for degradation. The execution of this complex machinery is guaranteed by the coordinated action of more than 40 ATG (autophagy-related) proteins that control the entire process at different stages from the biogenesis of the autophagosome to cargo sequestration and fusion with lysosomes. Autophagosome biogenesis occurs at multiple intracellular sites, such as the endoplasmic reticulum (ER) and the plasma membrane. Soon after the formation of the phagophore, the nascent autophagosome progressively grows in size and ultimately closes by recruiting intracellular membranes. In this review, we focus on the contribution of three membrane sources - the ER, the ER-Golgi intermediate compartment, and the Golgi complex - to autophagosome biogenesis and expansion. We also highlight the interplay between the secretory pathway and autophagy in cells when nutrients are scarce.
Collapse
Affiliation(s)
- Leopoldo Staiano
- Telethon Institute of Genetics and Medicine, Pozzuoli, Naples, Italy
| | - Francesca Zappa
- Telethon Institute of Genetics and Medicine, Pozzuoli, Naples, Italy.,Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA, USA
| |
Collapse
|
15
|
Dynamins 2 and 3 control the migration of human megakaryocytes by regulating CXCR4 surface expression and ITGB1 activity. Blood Adv 2019; 2:3540-3552. [PMID: 30538113 DOI: 10.1182/bloodadvances.2018021923] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Accepted: 11/04/2018] [Indexed: 12/14/2022] Open
Abstract
Megakaryocyte (MK) migration from the bone marrow periosteal niche toward the vascular niche is a prerequisite for proplatelet extension and release into the circulation. The mechanism for this highly coordinated process is poorly understood. Here we show that dynasore (DNSR), a small-molecule inhibitor of dynamins (DNMs), or short hairpin RNA knockdown of DNM2 and DNM3 impairs directional migration in a human MK cell line or MKs derived from cultured CD34+ cells. Because cell migration requires actin cytoskeletal rearrangements, we measured actin polymerization and the activity of cytoskeleton regulator RhoA and found them to be decreased after inhibition of DNM2 and DNM3. Because SDF-1α is important for hematopoiesis, we studied the expression of its receptor CXCR4 in DNSR-treated cells. CXCR4 expression on the cell surface was increased, at least partially because of slower endocytosis and internalization after SDF-1α treatment. Combined inhibition of DNM2 and DNM3 or forced expression of dominant-negative Dnm2-K44A or GTPase-defective DNM3 diminished β1 integrin (ITGB1) activity. DNSR-treated MKs showed an abnormally clustered staining pattern of Rab11, a marker of recycling endosomes. This suggests decreased recruitment of the recycling pathway in DNSR-treated cells. Altogether, we show that the GTPase activity of DNMs, which governs endocytosis and regulates cell receptor trafficking, exerts control on MK migration toward SDF-1α gradients, such as those originating from the vascular niche. DNMs play a critical role in MKs by triggering membrane-cytoskeleton rearrangements downstream of CXCR4 and integrins.
Collapse
|
16
|
Kardideh B, Samimi Z, Norooznezhad F, Kiani S, Mansouri K. Autophagy, cancer and angiogenesis: where is the link? Cell Biosci 2019; 9:65. [PMID: 31428311 PMCID: PMC6693242 DOI: 10.1186/s13578-019-0327-6] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Accepted: 08/04/2019] [Indexed: 01/12/2023] Open
Abstract
Background Autophagy is a catabolic process for degradation of intracellular components. Damaged proteins and organelles are engulfed in double-membrane vesicles ultimately fused with lysosomes. These vesicles, known as phagophores, develop to form autophagosomes. Encapsulated components are degraded after autophagosomes and lysosomes are fused. Autophagy clears denatured proteins and damaged organelles to produce macromolecules further reused by cells. This process is vital to cell homeostasis under both physiologic and pathologic conditions. Main body While the role of autophagy in cancer is quite controversial, the majority of studies introduce it as an anti-tumorigenesis mechanism. There are evidences confirming this role of autophagy in cancer. Mutations and monoallelic deletions have been demonstrated in autophagy-related genes correlating with cancer promotion. Another pathway through which autophagy suppresses tumorigenesis is cell cycle. On the other hand, under hypoxia and starvation condition, tumors use angiogenesis to provide nutrients. Also, autophagy flux is highlighted in vessel cell biology and vasoactive substances secretion from endothelial cells. The matrix proteoglycans such as Decorin and Perlecan could also interfere with angiogenesis and autophagy signaling pathway in endothelial cells (ECs). It seems that the connection between autophagy and angiogenesis in the tumor microenvironment is very important in determining the fate of cancer cells. Conclusion Matrix glycoproteins can regulate autophagy and angiogenesis linkage in tumor microenvironment. Also, finding details of how autophagy and angiogenesis correlate in cancer will help adopt more effective therapeutic approaches.
Collapse
Affiliation(s)
- Bahareh Kardideh
- 1Immunology Department, Faculty of Medicine, Kermanshah University of Medical Sciences, Kermanshah, Iran.,2Medical Biology Research Center, Health Technology Institute, Kermanshah University of Medical Sciences, Kermanshah, 6714967346 Iran
| | - Zahra Samimi
- 1Immunology Department, Faculty of Medicine, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Fatemeh Norooznezhad
- 2Medical Biology Research Center, Health Technology Institute, Kermanshah University of Medical Sciences, Kermanshah, 6714967346 Iran
| | - Sarah Kiani
- 2Medical Biology Research Center, Health Technology Institute, Kermanshah University of Medical Sciences, Kermanshah, 6714967346 Iran
| | - Kamran Mansouri
- 2Medical Biology Research Center, Health Technology Institute, Kermanshah University of Medical Sciences, Kermanshah, 6714967346 Iran.,3Molecular Medicine Department, Faculty of Medicine, Kermanshah University of Medical Sciences, Kermanshah, Iran
| |
Collapse
|
17
|
Judith D, Jefferies HBJ, Boeing S, Frith D, Snijders AP, Tooze SA. ATG9A shapes the forming autophagosome through Arfaptin 2 and phosphatidylinositol 4-kinase IIIβ. J Cell Biol 2019; 218:1634-1652. [PMID: 30917996 PMCID: PMC6504893 DOI: 10.1083/jcb.201901115] [Citation(s) in RCA: 127] [Impact Index Per Article: 25.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Revised: 02/28/2019] [Accepted: 03/14/2019] [Indexed: 12/24/2022] Open
Abstract
ATG9A is a multispanning membrane protein essential for autophagy. Normally resident in Golgi membranes and endosomes, during amino acid starvation, ATG9A traffics to sites of autophagosome formation. ATG9A is not incorporated into autophagosomes but is proposed to supply so-far-unidentified proteins and lipids to the autophagosome. To address this function of ATG9A, a quantitative analysis of ATG9A-positive compartments immunoisolated from amino acid-starved cells was performed. These ATG9A vesicles are depleted of Golgi proteins and enriched in BAR-domain containing proteins, Arfaptins, and phosphoinositide-metabolizing enzymes. Arfaptin2 regulates the starvation-dependent distribution of ATG9A vesicles, and these ATG9A vesicles deliver the PI4-kinase, PI4KIIIβ, to the autophagosome initiation site. PI4KIIIβ interacts with ATG9A and ATG13 to control PI4P production at the initiation membrane site and the autophagic response. PI4KIIIβ and PI4P likely function by recruiting the ULK1/2 initiation kinase complex subunit ATG13 to nascent autophagosomes.
Collapse
Affiliation(s)
- Delphine Judith
- Molecular Cell Biology of Autophagy, The Francis Crick Institute, London, UK
| | | | - Stefan Boeing
- Bioinformatics and Biostatistics, The Francis Crick Institute, London, UK
| | - David Frith
- Proteomics, The Francis Crick Institute, London, UK
| | | | - Sharon A Tooze
- Molecular Cell Biology of Autophagy, The Francis Crick Institute, London, UK
| |
Collapse
|
18
|
Zhang X, Wang L, Ireland SC, Ahat E, Li J, Bekier ME, Zhang Z, Wang Y. GORASP2/GRASP55 collaborates with the PtdIns3K UVRAG complex to facilitate autophagosome-lysosome fusion. Autophagy 2019; 15:1787-1800. [PMID: 30894053 DOI: 10.1080/15548627.2019.1596480] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
It has been indicated that the Golgi apparatus contributes to autophagy, but how it is involved in autophagosome formation and maturation is not well understood. Here we show that amino acid starvation causes trans-Golgi derived membrane fragments to colocalize with autophagosomes. Depletion of the Golgi stacking protein GORASP2/GRASP55, but not GORASP1/GRASP65, increases both MAP1LC3 (LC3)-II and SQSTM1/p62 levels. We demonstrate that GORASP2 facilitates autophagosome-lysosome fusion by physically linking autophagosomes and lysosomes through the interactions with LC3 on autophagosomes and LAMP2 on late endosomes/lysosomes. Furthermore, we provide evidence that GORASP2 interacts with BECN1 to facilitate the assembly and membrane association of the phosphatidylinositol 3-kinase (PtdIns3K) UVRAG complex. These findings indicate that GORASP2 plays an important role in autophagosome maturation during amino acid starvation. Abbreviations: ATG14: autophagy related 14; BafA1: bafilomycin A1; BSA: bovine serum albumin; CQ: chloroquine; EBSS: earle's balanced salt solution; EM: electron microscopy; EEA1: early endosome antigen 1; GFP: green fluorescent protein; GORASP1/GRASP65: golgi reassembly stacking protein 1; GORASP2/GRASP55: golgi reassembly stacking protein 2; LAMP1: lysosomal-associated membrane protein 1; LAMP2: lysosomal-associated membrane protein 2; MAP1LC3: microtubule associated protein 1 light chain 3; MTOR: mechanistic target of rapamycin kinase; PBS: phosphate-buffered saline; PtdIns3K: phosphatidylinositol 3-kinase; PtdIns3P: phosphatidylinositol 3-phosphate; PK: protease K; PNS: post-nuclear supernatant; RFP: red fluorescent protein; SD: standard deviation; TGN: trans-Golgi network; UVRAG: UV radiation resistance associated.
Collapse
Affiliation(s)
- Xiaoyan Zhang
- Department of Molecular, Cellular and Developmental Biology, University of Michigan , Ann Arbor , MI , USA
| | - Leibin Wang
- Department of Molecular, Cellular and Developmental Biology, University of Michigan , Ann Arbor , MI , USA
| | - Stephen C Ireland
- Department of Molecular, Cellular and Developmental Biology, University of Michigan , Ann Arbor , MI , USA
| | - Erpan Ahat
- Department of Molecular, Cellular and Developmental Biology, University of Michigan , Ann Arbor , MI , USA
| | - Jie Li
- Department of Molecular, Cellular and Developmental Biology, University of Michigan , Ann Arbor , MI , USA
| | - Michael E Bekier
- Department of Molecular, Cellular and Developmental Biology, University of Michigan , Ann Arbor , MI , USA
| | - Zhihai Zhang
- Department of Molecular, Cellular and Developmental Biology, University of Michigan , Ann Arbor , MI , USA
| | - Yanzhuang Wang
- Department of Molecular, Cellular and Developmental Biology, University of Michigan , Ann Arbor , MI , USA.,Department of Neurology, University of Michigan School of Medicine , Ann Arbor , MI , USA
| |
Collapse
|
19
|
Wei F, Duan Y. Crosstalk between Autophagy and Nanomaterials: Internalization, Activation, Termination. ACTA ACUST UNITED AC 2018; 3:e1800259. [PMID: 32627344 DOI: 10.1002/adbi.201800259] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Revised: 10/02/2018] [Indexed: 12/12/2022]
Abstract
Nanomaterials (NMs) are comprehensively applied in biomedicine due to their unique physical and chemical properties. Autophagy, as an evolutionarily conserved cellular quality control process, is closely associated with the effect of NMs on cells. In this review, the recent advances in NM-induced/inhibited autophagy (NM-phagy) are summarized, with an aim to present a comprehensive description of the mechanisms of NM-phagy from the perspective of internalization, activation, and termination, thereby bridging autophagy and nanomaterials. Several possible mechanisms are extensively reviewed including the endocytosis pathway of NMs and the related cross components (clathrin and adaptor protein 2 (AP-2), adenosine diphosphate (ADP)-ribosylation factor 6 (Arf6), Rab, UV radiation resistance associated gene (UVRAG)), three main stress mechanisms (oxidative stress, damaged organelles stress, and toxicity stress), and several signal pathway-related molecules. The mechanistic insight is beneficial to understand the autophagic response to NMs or NMs' regulation of autophagy. The challenges currently encountered and research trend in the field of NM-phagy are also highlighted. It is hoped that the NM-phagy discussion in this review with the focus on the mechanistic aspects may serve as a guideline for future research in this field.
Collapse
Affiliation(s)
- Fujing Wei
- Research Center of Analytical Instrumentation, Key Laboratory of Bio-resource and Eco-enviroment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610065, Sichuan, P. R. China
| | - Yixiang Duan
- Research Center of Analytical Instrumentation, Key Laboratory of Bio-resource and Eco-enviroment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610065, Sichuan, P. R. China
| |
Collapse
|
20
|
Zhuang X, Chung KP, Luo M, Jiang L. Autophagosome Biogenesis and the Endoplasmic Reticulum: A Plant Perspective. TRENDS IN PLANT SCIENCE 2018; 23:677-692. [PMID: 29929776 DOI: 10.1016/j.tplants.2018.05.002] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Revised: 04/19/2018] [Accepted: 05/01/2018] [Indexed: 05/20/2023]
Abstract
The autophagosome is a double-membrane compartment formed during autophagy that sequesters and delivers cargoes for their degradation or recycling into the vacuole. Analyses of the AuTophaGy-related (ATG) proteins have unveiled dynamic mechanisms for autophagosome biogenesis. Recent advances in plant autophagy research highlight a complex interplay between autophagosome biogenesis and the endoplasmic reticulum (ER): on the one hand ER serves as a membrane source for autophagosome initiation and a signaling platform for autophagy regulation; on the other hand ER turnover is connected to selective autophagy. We provide here an integrated view of ER-based autophagosome biogenesis in plants in comparison with the newest findings in yeast and mammals, with an emphasis on the hierarchy of the core ATG proteins, ATG9 trafficking, and ER-resident regulators in autophagy.
Collapse
Affiliation(s)
- Xiaohong Zhuang
- Center for Cell and Developmental Biology, State Key Laboratory of Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China; These authors contributed equally to this work.
| | - Kin Pan Chung
- Center for Cell and Developmental Biology, State Key Laboratory of Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China; Current address: Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1 14476, Potsdam-Golm, Germany; These authors contributed equally to this work
| | - Mengqian Luo
- Center for Cell and Developmental Biology, State Key Laboratory of Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Liwen Jiang
- Center for Cell and Developmental Biology, State Key Laboratory of Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China; The Chinese University of Hong Kong Shenzhen Research Institute, Shenzhen, China.
| |
Collapse
|
21
|
Abstract
Macroautophagy (hereafter autophagy) is a catabolic pathway present in all eukaryotic cells. The yeast Saccharomyces cerevisiae has been pivotal in the identification and characterization of the key autophagy-related (Atg) proteins, which play a central role in the generation of autophagosomes. The components of the core Atg/ATG machinery and their functions are highly conserved among species, although mammalian cells also have isoforms and auxiliary factors. Atg9/ATG9 is the only transmembrane protein that is part of the core Atg/ATG machinery, but it appears to have divergent localizations and molecular roles in yeast and mammals. A recent experimental analysis of the yeast endo-lysosomal system by the laboratory of Benjamin Glick, however, suggests a more simple organization of this membrane system. Although this study has not examined yeast Atg9, its findings place this protein in the same compartments as its mammalian counterpart. Here, we will discuss the implications of this conceptual change on the trafficking of yeast Atg9 and its function in autophagy.
Collapse
Affiliation(s)
- Christian Ungermann
- a Department of Biology/Chemistry, Biochemistry section , University of Osnabrück , Osnabrück , Germany
| | - Fulvio Reggiori
- b Department of Cell Biology , University of Groningen, University Medical Center Groningen , Groningen , The Netherlands
| |
Collapse
|
22
|
Takahashi Y, He H, Tang Z, Hattori T, Liu Y, Young MM, Serfass JM, Chen L, Gebru M, Chen C, Wills CA, Atkinson JM, Chen H, Abraham T, Wang HG. An autophagy assay reveals the ESCRT-III component CHMP2A as a regulator of phagophore closure. Nat Commun 2018; 9:2855. [PMID: 30030437 PMCID: PMC6054611 DOI: 10.1038/s41467-018-05254-w] [Citation(s) in RCA: 222] [Impact Index Per Article: 37.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Accepted: 06/23/2018] [Indexed: 01/21/2023] Open
Abstract
The mechanism of phagophore closure remains unclear due to technical limitations in distinguishing unclosed and closed autophagosomal membranes. Here, we report the HaloTag-LC3 autophagosome completion assay that specifically detects phagophores, nascent autophagosomes, and mature autophagic structures. Using this assay, we identify the endosomal sorting complexes required for transport (ESCRT)-III component CHMP2A as a critical regulator of phagophore closure. During autophagy, CHMP2A translocates to the phagophore and regulates the separation of the inner and outer autophagosomal membranes to form double-membrane autophagosomes. Consistently, inhibition of the AAA-ATPase VPS4 activity impairs autophagosome completion. The ESCRT-mediated membrane abscission appears to be a critical step in forming functional autolysosomes by preventing mislocalization of lysosome-associated membrane glycoprotein 1 to the inner autophagosomal membrane. Collectively, our work reveals a function for the ESCRT machinery in the final step of autophagosome formation and provides a useful tool for quantitative analysis of autophagosome biogenesis and maturation.
Collapse
Affiliation(s)
- Yoshinori Takahashi
- Department of Pediatrics, Penn State College of Medicine, Hershey, PA, 17033, USA.
| | - Haiyan He
- Department of Pediatrics, Penn State College of Medicine, Hershey, PA, 17033, USA
| | - Zhenyuan Tang
- Department of Pediatrics, Penn State College of Medicine, Hershey, PA, 17033, USA
| | - Tatsuya Hattori
- Department of Pediatrics, Penn State College of Medicine, Hershey, PA, 17033, USA
| | - Ying Liu
- Department of Pediatrics, Penn State College of Medicine, Hershey, PA, 17033, USA
| | - Megan M Young
- Department of Pediatrics, Penn State College of Medicine, Hershey, PA, 17033, USA
| | - Jacob M Serfass
- Department of Pharmacology, Penn State College of Medicine, Hershey, PA, 17033, USA
| | - Longgui Chen
- Department of Pediatrics, Penn State College of Medicine, Hershey, PA, 17033, USA
| | - Melat Gebru
- Department of Pediatrics, Penn State College of Medicine, Hershey, PA, 17033, USA
| | - Chong Chen
- Department of Pediatrics, Penn State College of Medicine, Hershey, PA, 17033, USA
| | - Carson A Wills
- Department of Pediatrics, Penn State College of Medicine, Hershey, PA, 17033, USA
| | - Jennifer M Atkinson
- Department of Pediatrics, Penn State College of Medicine, Hershey, PA, 17033, USA
| | - Han Chen
- Microscopy Imaging Facility, Penn State College of Medicine, Hershey, PA, 17033, USA
| | - Thomas Abraham
- Microscopy Imaging Facility, Penn State College of Medicine, Hershey, PA, 17033, USA
- Department of Neural and Behavioral Science, Penn State College of Medicine, Hershey, PA, 17033, USA
| | - Hong-Gang Wang
- Department of Pediatrics, Penn State College of Medicine, Hershey, PA, 17033, USA.
- Department of Pharmacology, Penn State College of Medicine, Hershey, PA, 17033, USA.
| |
Collapse
|
23
|
Rothe S, Prakash A, Tyedmers J. The Insoluble Protein Deposit (IPOD) in Yeast. Front Mol Neurosci 2018; 11:237. [PMID: 30050408 PMCID: PMC6052365 DOI: 10.3389/fnmol.2018.00237] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Accepted: 06/18/2018] [Indexed: 11/13/2022] Open
Abstract
The appearance of protein aggregates is a hallmark of several pathologies including many neurodegenerative diseases. Mounting evidence suggests that the accumulation of misfolded proteins into inclusions is a secondary line of defense when the extent of protein misfolding exceeds the capacity of the Protein Quality Control System, which mediates refolding or degradation of misfolded species. Such exhaustion can occur during severe proteotoxic stress, the excessive occurrence of aggregation prone protein species, e.g., amyloids, or during ageing. However, the machinery that mediates recognition, recruitment and deposition of different types of misfolded proteins into specific deposition sites is only poorly understood. Since emerging principles of aggregate deposition appear evolutionarily conserved, yeast represents a powerful model to study basic mechanisms of recognition of different types of misfolded proteins, their recruitment to the respective deposition site and the molecular organization at the corresponding site. Yeast possesses at least three different aggregate deposition sites, one of which is a major deposition site for amyloid aggregates termed Insoluble PrOtein Deposit (IPOD). Due to the link between neurodegenerative disease and accumulation of amyloid aggregates, the IPOD is of particular interest when we aim to identify the molecular mechanisms that cells have evolved to counteract toxicity associated with the occurrence of amyloid aggregates. Here, we will review what is known about IPOD composition and the mechanisms of recognition and recruitment of amyloid aggregates to this site in yeast. Finally, we will briefly discuss the possible physiological role of aggregate deposition at the IPOD.
Collapse
Affiliation(s)
- Stephanie Rothe
- Department of Medicine I and Clinical Chemistry, Heidelberg University Hospital, Heidelberg, Germany
| | - Abaya Prakash
- Department of Medicine I and Clinical Chemistry, Heidelberg University Hospital, Heidelberg, Germany
| | - Jens Tyedmers
- Department of Medicine I and Clinical Chemistry, Heidelberg University Hospital, Heidelberg, Germany
| |
Collapse
|
24
|
Abstract
Macroautophagy (herein referred to as autophagy) is a highly conserved stress response that engulfs damaged proteins, lipids, and/or organelles within double-membrane vesicles called autophagosomes for lysosomal degradation. Dysregulated autophagy is a hallmark of cancer; and thus, there is great interest in modulating autophagy for cancer therapy. Sphingolipids regulate each step of autophagosome biogenesis with roles for sphingolipid metabolites and enzymes spanning from the initial step of de novo ceramide synthesis to the sphingosine-1-phosphate lyase 1-mediated exit from the sphingolipid pathway. Notably, sphingolipid metabolism occurs at several of the organelles that contribute to autophagosome biogenesis to suggest that local changes in sphingolipids may regulate autophagy. As sphingolipid metabolism is frequently dysregulated in cancer, a molecular understanding of sphingolipids in stress-induced autophagy may provide insight into the mechanisms driving tumor development and progression. On the contrary, modulation of sphingolipid metabolites and/or enzymes can induce autophagy-dependent cell death for cancer therapy. This chapter will overview the major steps in mammalian autophagy, discuss the regulation of each step by sphingolipid metabolites, and describe the functions of sphingolipid-mediated autophagy in cancer. While our understanding of the signaling and biophysical properties of sphingolipids in autophagy remains in its infancy, the unique cross talk between the two pathways is an exciting area for further development, particularly in the context of cancer therapy.
Collapse
Affiliation(s)
- Megan M Young
- Department of Pediatrics, Pennsylvania State University College of Medicine, Hershey, PA, United States
| | - Hong-Gang Wang
- Department of Pediatrics, Pennsylvania State University College of Medicine, Hershey, PA, United States
| |
Collapse
|
25
|
Bingol B. Autophagy and lysosomal pathways in nervous system disorders. Mol Cell Neurosci 2018; 91:167-208. [PMID: 29729319 DOI: 10.1016/j.mcn.2018.04.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2017] [Revised: 04/26/2018] [Accepted: 04/28/2018] [Indexed: 12/12/2022] Open
Abstract
Autophagy is an evolutionarily conserved pathway for delivering cytoplasmic cargo to lysosomes for degradation. In its classically studied form, autophagy is a stress response induced by starvation to recycle building blocks for essential cellular processes. In addition, autophagy maintains basal cellular homeostasis by degrading endogenous substrates such as cytoplasmic proteins, protein aggregates, damaged organelles, as well as exogenous substrates such as bacteria and viruses. Given their important role in homeostasis, autophagy and lysosomal machinery are genetically linked to multiple human disorders such as chronic inflammatory diseases, cardiomyopathies, cancer, and neurodegenerative diseases. Multiple targets within the autophagy and lysosomal pathways offer therapeutic opportunities to benefit patients with these disorders. Here, I will summarize the mechanisms of autophagy pathways, the evidence supporting a pathogenic role for disturbed autophagy and lysosomal degradation in nervous system disorders, and the therapeutic potential of autophagy modulators in the clinic.
Collapse
Affiliation(s)
- Baris Bingol
- Genentech, Inc., Department of Neuroscience, 1 DNA Way, South San Francisco 94080, United States.
| |
Collapse
|
26
|
Yu L, Chen Y, Tooze SA. Autophagy pathway: Cellular and molecular mechanisms. Autophagy 2017; 14:207-215. [PMID: 28933638 PMCID: PMC5902171 DOI: 10.1080/15548627.2017.1378838] [Citation(s) in RCA: 942] [Impact Index Per Article: 134.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Revised: 08/04/2017] [Accepted: 09/07/2017] [Indexed: 02/06/2023] Open
Abstract
Macroautophagy/autophagy is an essential, conserved self-eating process that cells perform to allow degradation of intracellular components, including soluble proteins, aggregated proteins, organelles, macromolecular complexes, and foreign bodies. The process requires formation of a double-membrane structure containing the sequestered cytoplasmic material, the autophagosome, that ultimately fuses with the lysosome. This review will define this process and the cellular pathways required, from the formation of the double membrane to the fusion with lysosomes in molecular terms, and in particular highlight the recent progress in our understanding of this complex process.
Collapse
Affiliation(s)
- Li Yu
- State Key Laboratory of Membrane Biology, Tsinghua University-Peking University Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China
| | - Yang Chen
- State Key Laboratory of Membrane Biology, Tsinghua University-Peking University Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China
| | - Sharon A. Tooze
- Molecular Cell Biology of Autophagy, The Francis Crick Institute, London, United Kingdom
| |
Collapse
|
27
|
Autophagy in the context of the cellular membrane-trafficking system: the enigma of Atg9 vesicles. Biochem Soc Trans 2017; 45:1323-1331. [PMID: 29150528 PMCID: PMC5730941 DOI: 10.1042/bst20170128] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2017] [Revised: 10/11/2017] [Accepted: 10/16/2017] [Indexed: 12/15/2022]
Abstract
Macroautophagy is an intracellular degradation system that involves the de novo formation of membrane structures called autophagosomes, although the detailed process by which membrane lipids are supplied during autophagosome formation is yet to be elucidated. Macroautophagy is thought to be associated with canonical membrane trafficking, but several mechanistic details are still missing. In this review, the current understanding and potential mechanisms by which membrane trafficking participates in macroautophagy are described, with a focus on the enigma of the membrane protein Atg9, for which the proximal mechanisms determining its movement are disputable, despite its key role in autophagosome formation.
Collapse
|
28
|
PI3K-C2α knockdown decreases autophagy and maturation of endocytic vesicles. PLoS One 2017; 12:e0184909. [PMID: 28910396 PMCID: PMC5599018 DOI: 10.1371/journal.pone.0184909] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Accepted: 09/01/2017] [Indexed: 12/26/2022] Open
Abstract
Phosphoinositide 3-kinase (PI3K) family members are involved in diverse cellular fates including cell growth, proliferation, and survival. While many molecular details are known about the Class I and III PI3Ks, less is known about the Class II PI3Ks. To explore the function of all eight PI3K isoforms in autophagy, we knock down each gene individually and measure autophagy. We find a significant decrease in autophagy following siRNA-mediated PIK3C2A (encoding the Class 2 PI3K, PI3K-C2α) knockdown. This defective autophagy is rescued by exogenous PI3K-C2α, but not kinase-dead PI3K-C2α. Using confocal microscopy, we probe for markers of endocytosis and autophagy, revealing that PI3K-C2α colocalizes with markers of endocytosis. Though endocytic uptake is intact, as demonstrated by transferrin labeling, PIK3C2A knockdown results in vesicle accumulation at the recycling endosome. We isolate distinct membrane sources and observe that PI3K-C2α interacts with markers of endocytosis and autophagy, notably ATG9. Knockdown of either PIK3C2A or ATG9A/B, but not PI3KC3, results in an accumulation of transferrin-positive clathrin coated vesicles and RAB11-positive vesicles at the recycling endosome. Taken together, these results support a role for PI3K-C2α in the proper maturation of endosomes, and suggest that PI3K-C2α may be a critical node connecting the endocytic and autophagic pathways.
Collapse
|
29
|
Kakuta S, Yamaguchi J, Suzuki C, Sasaki M, Kazuno S, Uchiyama Y. Small GTPase Rab1B is associated with ATG9A vesicles and regulates autophagosome formation. FASEB J 2017; 31:3757-3773. [PMID: 28522593 DOI: 10.1096/fj.201601052r] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Accepted: 04/24/2017] [Indexed: 11/11/2022]
Abstract
ATG9 is a membrane protein that is essential for autophagy and is considered to be directly involved in the early steps of autophagosome formation. Yeast Atg9 is mainly localized to small vesicles (Atg9 vesicles), whereas mammalian ATG9A is reportedly localized to the trans-Golgi network, the endosomal compartment, and other unidentified membrane structures. To dissect the ATG9A-containing membranes, we examined the subcellular localization of ATG9A and performed immunoisolation of those membranes. ATG9A-green fluorescent protein in human culture cells was observed as numerous puncta that move rapidly throughout the cytoplasm. We isolated these cytoplasmic membranes and found that they were small vesicles that resemble the yeast Atg9 vesicle. One of the proteins obtained via proteomic analyses of the mammalian ATG9A vesicle was Rab1, a small GTPase that is essential in endoplasmic reticulum-to-Golgi vesicle trafficking. Knockdown studies of Rab1B showed a suppression of autophagy. In these Rab1B-depleted cells, ATG9A accumulated in intermediate membrane structures at autophagosome formation sites. These results indicate that Rab1B is involved in regulating the proper development of autophagosomes.-Kakuta, S., Yamaguchi, J., Suzuki, C., Sasaki, M., Kazuno, S., Uchiyama, Y. Small GTPase Rab1B is associated with ATG9A vesicles and regulates autophagosome formation.
Collapse
Affiliation(s)
- Soichiro Kakuta
- Department of Cellular and Molecular Neuropathology, Juntendo University Graduate School of Medicine, Tokyo, Japan
- Laboratory of Morphology and Image Analysis, Research Support Center, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Junji Yamaguchi
- Department of Cellular and Molecular Neuropathology, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Chigure Suzuki
- Department of Cellular and Molecular Neuropathology, Juntendo University Graduate School of Medicine, Tokyo, Japan
- Department of Cellular and Molecular Pharmacology, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Mitsuho Sasaki
- Laboratory of Animal Models for Human Diseases, National Institute of Biomedical Innovation, Health and Nutrition, Osaka, Japan
| | - Saiko Kazuno
- Laboratory of Proteomics and Biomolecular Science, Research Support Center, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Yasuo Uchiyama
- Department of Cellular and Molecular Neuropathology, Juntendo University Graduate School of Medicine, Tokyo, Japan;
| |
Collapse
|
30
|
Tang Z, Takahashi Y, Chen C, Liu Y, He H, Tsotakos N, Serfass JM, Gebru MT, Chen H, Young MM, Wang HG. Atg2A/B deficiency switches cytoprotective autophagy to non-canonical caspase-8 activation and apoptosis. Cell Death Differ 2017; 24:2127-2138. [PMID: 28800131 DOI: 10.1038/cdd.2017.133] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Revised: 06/30/2017] [Accepted: 07/10/2017] [Indexed: 12/13/2022] Open
Abstract
Autophagosomal membranes are emerging as platforms for various cell survival and death signaling networks beyond autophagy. While autophagy-dependent cell death has been reported in response to a variety of stimuli, the underlying molecular mechanisms remain far from clear. Here, we demonstrate that inhibition of autophagosome completion by Atg2A/B deletion accumulates immature autophagosomal membranes that promote non-canonical caspase-8 activation in response to nutrient starvation via an intracellular death-inducing signaling complex (iDISC). Importantly, iDISC-induced caspase-8 dimerization and activation occurs on accumulated autophagosomal membranes and requires the LC3 conjugation machinery but is independent from the extrinsic pathway of apoptosis. Moreover, we have identified NF-κB signaling and c-FLIP as negative regulators of iDISC-mediated caspase-8 activation and apoptosis. Collectively, these findings reveal autophagosomal membrane completion as a novel target to switch cytoprotective autophagy to apoptosis.
Collapse
Affiliation(s)
- Zhenyuan Tang
- Department of Pediatrics, Penn State University College of Medicine, Hershey, PA, USA
| | - Yoshinori Takahashi
- Department of Pediatrics, Penn State University College of Medicine, Hershey, PA, USA
| | - Chong Chen
- Department of Pediatrics, Penn State University College of Medicine, Hershey, PA, USA
| | - Ying Liu
- Department of Pharmacology, Penn State University College of Medicine, Hershey, PA, USA
| | - Haiyan He
- Department of Pediatrics, Penn State University College of Medicine, Hershey, PA, USA
| | - Nikolaos Tsotakos
- Department of Pediatrics, Penn State University College of Medicine, Hershey, PA, USA
| | - Jacob M Serfass
- Department of Pharmacology, Penn State University College of Medicine, Hershey, PA, USA
| | - Melat T Gebru
- Department of Pediatrics, Penn State University College of Medicine, Hershey, PA, USA
| | - Han Chen
- The Microscopy Imaging Facility, Penn State University College of Medicine, Hershey, PA, USA
| | - Megan M Young
- Department of Pediatrics, Penn State University College of Medicine, Hershey, PA, USA
| | - Hong-Gang Wang
- Department of Pediatrics, Penn State University College of Medicine, Hershey, PA, USA.,Department of Pharmacology, Penn State University College of Medicine, Hershey, PA, USA
| |
Collapse
|
31
|
Davis S, Wang J, Ferro-Novick S. Crosstalk between the Secretory and Autophagy Pathways Regulates Autophagosome Formation. Dev Cell 2017; 41:23-32. [PMID: 28399396 DOI: 10.1016/j.devcel.2017.03.015] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2016] [Revised: 02/26/2017] [Accepted: 03/16/2017] [Indexed: 12/26/2022]
Abstract
The induction of autophagy by nutrient deprivation leads to a rapid increase in the formation of autophagosomes, unique organelles that replenish the cellular pool of nutrients by sequestering cytoplasmic material for degradation. The urgent need for membranes to form autophagosomes during starvation to maintain homeostasis leads to a dramatic rearrangement of intracellular membranes. Here we discuss recent findings that have begun to uncover how different parts of the secretory pathway directly and indirectly contribute to autophagosome formation during starvation.
Collapse
Affiliation(s)
- Saralin Davis
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, CA 92093-0668, USA
| | - Juan Wang
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, CA 92093-0668, USA
| | - Susan Ferro-Novick
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, CA 92093-0668, USA.
| |
Collapse
|
32
|
Li J, Barylko B, Eichorst JP, Mueller JD, Albanesi JP, Chen Y. Association of Endophilin B1 with Cytoplasmic Vesicles. Biophys J 2017; 111:565-576. [PMID: 27508440 DOI: 10.1016/j.bpj.2016.06.017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Revised: 06/14/2016] [Accepted: 06/16/2016] [Indexed: 01/21/2023] Open
Abstract
Endophilins are SH3- and BAR domain-containing proteins implicated in membrane remodeling and vesicle formation. Endophilins A1 and A2 promote the budding of endocytic vesicles from the plasma membrane, whereas endophilin B1 has been implicated in vesicle budding from intracellular organelles, including the trans-Golgi network and late endosomes. We previously reported that endophilins A1 and A2 exist almost exclusively as soluble dimers in the cytosol. Here, we present results of fluorescence fluctuation spectroscopy analyses indicating that, in contrast, the majority of endophilin B1 is present in multiple copies on small, highly mobile cytoplasmic vesicles. Formation of these vesicles was enhanced by overexpression of wild-type dynamin 2, but suppressed by expression of a catalytically inactive dynamin 2 mutant. Using dual-color heterospecies partition analysis, we identified the epidermal growth factor receptor on endophilin B1 vesicles. Moreover, a proportion of endophilin B1 vesicles also contained caveolin, whereas clathrin was almost undetectable on those vesicles. These results raise the possibility that endophilin B1 participates in dynamin 2-dependent formation of a population of transport vesicles distinct from those generated by A-type endophilins.
Collapse
Affiliation(s)
- Jinhui Li
- Department of Physics, University of Minnesota, Minneapolis, Minnesota
| | | | - John P Eichorst
- Department of Physics, University of Minnesota, Minneapolis, Minnesota
| | - Joachim D Mueller
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota
| | | | - Yan Chen
- Department of Physics, University of Minnesota, Minneapolis, Minnesota.
| |
Collapse
|
33
|
Serfass JM, Takahashi Y, Zhou Z, Kawasawa YI, Liu Y, Tsotakos N, Young MM, Tang Z, Yang L, Atkinson JM, Chroneos ZC, Wang HG. Endophilin B2 facilitates endosome maturation in response to growth factor stimulation, autophagy induction, and influenza A virus infection. J Biol Chem 2017; 292:10097-10111. [PMID: 28455444 PMCID: PMC5473216 DOI: 10.1074/jbc.m117.792747] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Revised: 04/27/2017] [Indexed: 12/19/2022] Open
Abstract
Endocytosis, and the subsequent trafficking of endosomes, requires dynamic physical alterations in membrane shape that are mediated in part by endophilin proteins. The endophilin B family of proteins contains an N-terminal Bin/amphiphysin/Rvs (N-BAR) domain that induces membrane curvature to regulate intracellular membrane dynamics. Whereas endophilin B1 (SH3GLB1/Bif-1) is known to be involved in a number of cellular processes, including apoptosis, autophagy, and endocytosis, the cellular function of endophilin B2 (SH3GLB2) is not well understood. In this study, we used genetic approaches that revealed that endophilin B2 is not required for embryonic development in vivo but that endophilin B2 deficiency impairs endosomal trafficking in vitro, as evidenced by suppressed endosome acidification, EGFR degradation, autophagic flux, and influenza A viral RNA nuclear entry and replication. Mechanistically, although the loss of endophilin B2 did not affect endocytic internalization and lysosomal function, endophilin B2 appeared to regulate the trafficking of endocytic vesicles and autophagosomes to late endosomes or lysosomes. Moreover, we also found that despite having an intracellular localization and tissue distribution similar to endophilin B1, endophilin B2 is dispensable for mitochondrial apoptosis. Taken together, our findings suggest that endophilin B2 positively regulates the endocytic pathway in response to growth factor signaling, autophagy induction, and viral entry.
Collapse
Affiliation(s)
| | | | - Zhixiang Zhou
- the Department of Pediatrics
- the College of Life Science and Bioengineering, Beijing University of Technology, Beijing 100124, China
| | - Yuka Imamura Kawasawa
- From the Department of Pharmacology
- the Institute for Personalized Medicine, Department of Biochemistry and Molecular Biology, and
| | - Ying Liu
- From the Department of Pharmacology
| | | | | | | | | | | | - Zissis C Chroneos
- the Department of Pediatrics
- the Department of Microbiology & Immunology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033 and
| | - Hong-Gang Wang
- From the Department of Pharmacology,
- the Department of Pediatrics
| |
Collapse
|
34
|
Schott MB, Rasineni K, Weller SG, Schulze RJ, Sletten AC, Casey CA, McNiven MA. β-Adrenergic induction of lipolysis in hepatocytes is inhibited by ethanol exposure. J Biol Chem 2017; 292:11815-11828. [PMID: 28515323 DOI: 10.1074/jbc.m117.777748] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Revised: 05/05/2017] [Indexed: 12/21/2022] Open
Abstract
In liver steatosis (i.e. fatty liver), hepatocytes accumulate many large neutral lipid storage organelles known as lipid droplets (LDs). LDs are important in the maintenance of energy homeostasis, but the signaling mechanisms that stimulate LD metabolism in hepatocytes are poorly defined. In adipocytes, catecholamines target the β-adrenergic (β-AR)/cAMP pathway to activate cytosolic lipases and induce their recruitment to the LD surface. Therefore, the goal of this study was to determine whether hepatocytes, like adipocytes, also undergo cAMP-mediated lipolysis in response to β-AR stimulation. Using primary rat hepatocytes and human hepatoma cells, we found that treatment with the β-AR agent isoproterenol caused substantial LD loss via activation of cytosolic lipases adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL). β-Adrenergic stimulation rapidly activated PKA, which led to the phosphorylation of ATGL and HSL and their recruitment to the LD surface. To test whether this β-AR-dependent lipolysis pathway was altered in a model of alcoholic fatty liver, primary hepatocytes from rats fed a 6-week EtOH-containing Lieber-DeCarli diet were treated with cAMP agonists. Compared with controls, EtOH-exposed hepatocytes showed a drastic inhibition in β-AR/cAMP-induced LD breakdown and the phosphorylation of PKA substrates, including HSL. This observation was supported in VA-13 cells, an EtOH-metabolizing human hepatoma cell line, which displayed marked defects in both PKA activation and isoproterenol-induced ATGL translocation to the LD periphery. In summary, these findings suggest that β-AR stimulation mobilizes cytosolic lipases for LD breakdown in hepatocytes, and perturbation of this pathway could be a major consequence of chronic EtOH insult leading to fatty liver.
Collapse
Affiliation(s)
- Micah B Schott
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota 55905
| | - Karuna Rasineni
- Department of Internal Medicine, University of Nebraska Medical Center, Omaha, Nebraska 68198
| | - Shaun G Weller
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota 55905
| | - Ryan J Schulze
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota 55905
| | - Arthur C Sletten
- Division of Gastroenterology & Hepatology, Center for Basic Research in Digestive Diseases, Mayo Clinic, Rochester, Minnesota 55905
| | - Carol A Casey
- Department of Internal Medicine, University of Nebraska Medical Center, Omaha, Nebraska 68198; Nebraska Western Iowa Health Care System Research Service, Omaha, Nebraska 68105
| | - Mark A McNiven
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota 55905.
| |
Collapse
|
35
|
Haidar M, Timmerman V. Autophagy as an Emerging Common Pathomechanism in Inherited Peripheral Neuropathies. Front Mol Neurosci 2017; 10:143. [PMID: 28553203 PMCID: PMC5425483 DOI: 10.3389/fnmol.2017.00143] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Accepted: 04/26/2017] [Indexed: 12/16/2022] Open
Abstract
The inherited peripheral neuropathies (IPNs) comprise a growing list of genetically heterogeneous diseases. With mutations in more than 80 genes being reported to cause IPNs, a wide spectrum of functional consequences is expected to follow this genotypic diversity. Hence, the search for a common pathomechanism among the different phenotypes has become the holy grail of functional research into IPNs. During the last decade, studies on several affected genes have shown a direct and/or indirect correlation with autophagy. Autophagy, a cellular homeostatic process, is required for the removal of cell aggregates, long-lived proteins and dead organelles from the cell in double-membraned vesicles destined for the lysosomes. As an evolutionarily highly conserved process, autophagy is essential for the survival and proper functioning of the cell. Recently, neuronal cells have been shown to be particularly vulnerable to disruption of the autophagic pathway. Furthermore, autophagy has been shown to be affected in various common neurodegenerative diseases of both the central and the peripheral nervous system including Alzheimer's, Parkinson's, and Huntington's diseases. In this review we provide an overview of the genes involved in hereditary neuropathies which are linked to autophagy and we propose the disruption of the autophagic flux as an emerging common pathomechanism. We also shed light on the different steps of the autophagy pathway linked to these genes. Finally, we review the concept of autophagy being a therapeutic target in IPNs, and the possibilities and challenges of this pathway-specific targeting.
Collapse
Affiliation(s)
- Mansour Haidar
- Peripheral Neuropathy Research Group, Institute Born Bunge, University of AntwerpAntwerpen, Belgium
| | - Vincent Timmerman
- Peripheral Neuropathy Research Group, Institute Born Bunge, University of AntwerpAntwerpen, Belgium
| |
Collapse
|
36
|
Liu X, Rothe K, Yen R, Fruhstorfer C, Maetzig T, Chen M, Forrest DL, Humphries RK, Jiang X. A novel AHI-1-BCR-ABL-DNM2 complex regulates leukemic properties of primitive CML cells through enhanced cellular endocytosis and ROS-mediated autophagy. Leukemia 2017; 31:2376-2387. [PMID: 28366933 PMCID: PMC5668499 DOI: 10.1038/leu.2017.108] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2016] [Revised: 03/17/2017] [Accepted: 03/22/2017] [Indexed: 02/07/2023]
Abstract
Tyrosine kinase inhibitor (TKI) therapies induce clinical remission with remarkable effects on chronic myeloid leukemia (CML). However, very few TKIs completely eradicate the leukemic clone and persistence of leukemic stem cells (LSCs) remains challenging, warranting new, distinct targets for improved treatments. We demonstrated that the scaffold protein AHI-1 is highly deregulated in LSCs and interacts with multiple proteins, including Dynamin-2 (DNM2), to mediate TKI-resistance of LSCs. We have now demonstrated that the SH3 domain of AHI-1 and the proline rich domain of DNM2 are mainly responsible for this interaction. DNM2 expression was significantly increased in CML stem/progenitor cells; knockdown of DNM2 greatly impaired their survival and sensitized them to TKI treatments. Importantly, a new AHI-1-BCR-ABL-DNM2 protein complex was uncovered, which regulates leukemic properties of these cells through a unique mechanism of cellular endocytosis and ROS-mediated autophagy. Thus, targeting this complex may facilitate eradication of LSCs for curative therapies.
Collapse
Affiliation(s)
- X Liu
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, BC, Canada.,Department of Medicine, University of British Columbia, Vancouver, BC, Canada
| | - K Rothe
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, BC, Canada.,Department of Medical Genetics, University of British Columbia, Vancouver, BC, Canada
| | - R Yen
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, BC, Canada.,Department of Medicine, University of British Columbia, Vancouver, BC, Canada
| | - C Fruhstorfer
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, BC, Canada
| | - T Maetzig
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, BC, Canada
| | - M Chen
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, BC, Canada
| | - D L Forrest
- Department of Medicine, University of British Columbia, Vancouver, BC, Canada.,Leukemia/BMT Program of British Columbia, Vancouver, BC, Canada
| | - R K Humphries
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, BC, Canada.,Department of Medicine, University of British Columbia, Vancouver, BC, Canada
| | - X Jiang
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, BC, Canada.,Department of Medicine, University of British Columbia, Vancouver, BC, Canada.,Department of Medical Genetics, University of British Columbia, Vancouver, BC, Canada
| |
Collapse
|
37
|
Nguyen N, Shteyn V, Melia TJ. Sensing Membrane Curvature in Macroautophagy. J Mol Biol 2017; 429:457-472. [PMID: 28088480 PMCID: PMC5276735 DOI: 10.1016/j.jmb.2017.01.006] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Revised: 01/07/2017] [Accepted: 01/08/2017] [Indexed: 10/20/2022]
Abstract
In response to intracellular stress events ranging from starvation to pathogen invasion, the cell activates one or more forms of macroautophagy. The key event in these related pathways is the de novo formation of a new organelle called the autophagosome, which either surrounds and sequesters random portions of the cytoplasm or selectively targets individual intracellular challenges. Thus, the autophagosome is a flexible membrane platform with dimensions that ultimately depend upon the target cargo. The intermediate membrane, termed the phagophore or isolation membrane, is a cup-like structure with a clear concave face and a highly curved rim. The phagophore is largely devoid of integral membrane proteins; thus, its shape and size are governed by peripherally associated membrane proteins and possibly by the lipid composition of the membrane itself. Growth along the phagophore rim marks the progress of both organelle expansion and ultimately organelle closure around a particular cargo. These two properties, a reliance on peripheral membrane proteins and a structurally distinct membrane architecture, suggest that the ability to target or manipulate membrane curvature might be an essential activity of proteins functioning in this pathway. In this review, we discuss the extent to which membranes are naturally curved at each of the cellular sites believed to engage in autophagosome formation, review basic mechanisms used to sense this curvature, and then summarize the existing literature concerning which autophagy proteins are capable of curvature recognition.
Collapse
Affiliation(s)
- Nathan Nguyen
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520, USA.
| | - Vladimir Shteyn
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520, USA.
| | - Thomas J Melia
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520, USA.
| |
Collapse
|
38
|
Staudt C, Gilis F, Tevel V, Jadot M, Boonen M. A conserved glycine residue in the C-terminal region of human ATG9A is required for its transport from the endoplasmic reticulum to the Golgi apparatus. Biochem Biophys Res Commun 2016; 479:404-409. [PMID: 27663665 DOI: 10.1016/j.bbrc.2016.09.097] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Accepted: 09/19/2016] [Indexed: 10/21/2022]
Abstract
ATG9A is the only polytopic protein of the mammalian autophagy-related protein family whose members regulate autophagosome formation during macroautophagy. At steady state, ATG9A localizes to several intracellular sites, including the Golgi apparatus, endosomes and the plasma membrane, and it redistributes towards autophagosomes upon autophagy induction. Interestingly, the transport of yeast Atg9 to the pre-autophagosomal structure depends on its self-association, which is mediated by a short amino acid motif located in the C-terminal region of the protein. Here, we investigated whether the residues that align with this motif in human ATG9A (V515-C519) are also required for its trafficking in mammalian cells. Interestingly, our findings support that human ATG9A self-interacts as well, and that this process promotes transport of ATG9A molecules through the Golgi apparatus. Furthermore, our data reveal that the transport of ATG9A out of the ER is severely impacted after mutation of the conserved V515-C519 motif. Nevertheless, the mutated ATG9A molecules could still interact with each other, indicating that the molecular mechanism of self-interaction differs in mammalian cells compared to yeast. Using sequential amino acid substitutions of glycine 516 and cysteine 519, we found that the stability of ATG9A relies on both of these residues, but that only the former is required for efficient transport of human ATG9A from the endoplasmic reticulum to the Golgi apparatus.
Collapse
Affiliation(s)
- Catherine Staudt
- URPhyM-Laboratoire de Chimie Physiologique, University of Namur, 61 Rue de Bruxelles, 5000 Namur, Belgium
| | - Florentine Gilis
- URPhyM-Laboratoire de Chimie Physiologique, University of Namur, 61 Rue de Bruxelles, 5000 Namur, Belgium
| | - Virginie Tevel
- URPhyM-Laboratoire de Chimie Physiologique, University of Namur, 61 Rue de Bruxelles, 5000 Namur, Belgium
| | - Michel Jadot
- URPhyM-Laboratoire de Chimie Physiologique, University of Namur, 61 Rue de Bruxelles, 5000 Namur, Belgium
| | - Marielle Boonen
- URPhyM-Laboratoire de Chimie Physiologique, University of Namur, 61 Rue de Bruxelles, 5000 Namur, Belgium.
| |
Collapse
|