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Su Y, Bu F, Zhu Y, Yang L, Wu Q, Zheng Y, Zhao J, Yu L, Jiang N, Wang Y, Wu J, Xie Y, Zhang X, Gao Y, Lan K, Deng Q. Hepatitis B virus core protein as a Rab-GAP suppressor driving liver disease progression. Sci Bull (Beijing) 2024; 69:2580-2595. [PMID: 38670853 DOI: 10.1016/j.scib.2024.04.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Revised: 02/28/2024] [Accepted: 03/25/2024] [Indexed: 04/28/2024]
Abstract
Chronic hepatitis B virus (HBV) infection can lead to advanced liver pathology. Here, we establish a transgenic murine model expressing a basic core promoter (BCP)-mutated HBV genome. Unlike previous studies on the wild-type virus, the BCP-mutated HBV transgenic mice manifest chronic liver injury that culminates in cirrhosis and tumor development with age. Notably, agonistic anti-Fas treatment induces fulminant hepatitis in these mice even at a negligible dose. As the BCP mutant exhibits a striking increase in HBV core protein (HBc) expression, we posit that HBc is actively involved in hepatocellular injury. Accordingly, HBc interferes with Fis1-stimulated mitochondrial recruitment of Tre-2/Bub2/Cdc16 domain family member 15 (TBC1D15). HBc may also inhibit multiple Rab GTPase-activating proteins, including Rab7-specific TBC1D15 and TBC1D5, by binding to their conserved catalytic domain. In cells under mitochondrial stress, HBc thus perturbs mitochondrial dynamics and prevents the recycling of damaged mitochondria. Moreover, sustained HBc expression causes lysosomal consumption via Rab7 hyperactivation, which further hampers late-stage autophagy and substantially increases apoptotic cell death. Finally, we show that adenovirally expressed HBc in a mouse model is directly cytopathic and causes profound liver injury, independent of antigen-specific immune clearance. These findings reveal an unexpected cytopathic role of HBc, making it a pivotal target for HBV-associated liver disease treatment. The BCP-mutated HBV transgenic mice also provide a valuable model for understanding chronic hepatitis B progression and for the assessment of therapeutic strategies.
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Affiliation(s)
- Yu Su
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), School of Basic Medical Sciences, Shanghai Institute of Infectious Disease and Biosecurity, Fudan University, Shanghai 200032, China; Shanghai Frontiers Science Center of Pathogenic Microorganisms and Infection, Fudan University, Shanghai 200032, China
| | - Fan Bu
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), School of Basic Medical Sciences, Shanghai Institute of Infectious Disease and Biosecurity, Fudan University, Shanghai 200032, China; Shanghai Frontiers Science Center of Pathogenic Microorganisms and Infection, Fudan University, Shanghai 200032, China
| | - Yuanfei Zhu
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), School of Basic Medical Sciences, Shanghai Institute of Infectious Disease and Biosecurity, Fudan University, Shanghai 200032, China; Shanghai Frontiers Science Center of Pathogenic Microorganisms and Infection, Fudan University, Shanghai 200032, China; Laboratory of Cellular Immunity, Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai 201203, China
| | - Le Yang
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), School of Basic Medical Sciences, Shanghai Institute of Infectious Disease and Biosecurity, Fudan University, Shanghai 200032, China; Shanghai Frontiers Science Center of Pathogenic Microorganisms and Infection, Fudan University, Shanghai 200032, China
| | - Qiong Wu
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), School of Basic Medical Sciences, Shanghai Institute of Infectious Disease and Biosecurity, Fudan University, Shanghai 200032, China; Shanghai Frontiers Science Center of Pathogenic Microorganisms and Infection, Fudan University, Shanghai 200032, China
| | - Yuan Zheng
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), School of Basic Medical Sciences, Shanghai Institute of Infectious Disease and Biosecurity, Fudan University, Shanghai 200032, China; Shanghai Frontiers Science Center of Pathogenic Microorganisms and Infection, Fudan University, Shanghai 200032, China
| | - Jianjin Zhao
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), School of Basic Medical Sciences, Shanghai Institute of Infectious Disease and Biosecurity, Fudan University, Shanghai 200032, China; Shanghai Frontiers Science Center of Pathogenic Microorganisms and Infection, Fudan University, Shanghai 200032, China
| | - Lin Yu
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), School of Basic Medical Sciences, Shanghai Institute of Infectious Disease and Biosecurity, Fudan University, Shanghai 200032, China; Shanghai Frontiers Science Center of Pathogenic Microorganisms and Infection, Fudan University, Shanghai 200032, China
| | - Nan Jiang
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), School of Basic Medical Sciences, Shanghai Institute of Infectious Disease and Biosecurity, Fudan University, Shanghai 200032, China; Shanghai Frontiers Science Center of Pathogenic Microorganisms and Infection, Fudan University, Shanghai 200032, China
| | - Yongxiang Wang
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), School of Basic Medical Sciences, Shanghai Institute of Infectious Disease and Biosecurity, Fudan University, Shanghai 200032, China
| | - Jian Wu
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), School of Basic Medical Sciences, Shanghai Institute of Infectious Disease and Biosecurity, Fudan University, Shanghai 200032, China
| | - Youhua Xie
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), School of Basic Medical Sciences, Shanghai Institute of Infectious Disease and Biosecurity, Fudan University, Shanghai 200032, China; Shanghai Frontiers Science Center of Pathogenic Microorganisms and Infection, Fudan University, Shanghai 200032, China
| | - Xinxin Zhang
- Department of Infectious Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Yueqiu Gao
- Laboratory of Cellular Immunity, Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai 201203, China.
| | - Ke Lan
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China.
| | - Qiang Deng
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), School of Basic Medical Sciences, Shanghai Institute of Infectious Disease and Biosecurity, Fudan University, Shanghai 200032, China; Shanghai Frontiers Science Center of Pathogenic Microorganisms and Infection, Fudan University, Shanghai 200032, China.
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2
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Mulligan RJ, Magaj MM, Digilio L, Redemann S, Yap CC, Winckler B. Collapse of late endosomal pH elicits a rapid Rab7 response via the V-ATPase and RILP. J Cell Sci 2024; 137:jcs261765. [PMID: 38578235 PMCID: PMC11166203 DOI: 10.1242/jcs.261765] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Accepted: 03/26/2024] [Indexed: 04/06/2024] Open
Abstract
Endosomal-lysosomal trafficking is accompanied by the acidification of endosomal compartments by the H+-V-ATPase to reach low lysosomal pH. Disruption of the correct pH impairs lysosomal function and the balance of protein synthesis and degradation (proteostasis). Here, we treated mammalian cells with the small dipeptide LLOMe, which is known to permeabilize lysosomal membranes, and find that LLOMe also impacts late endosomes (LEs) by neutralizing their pH without causing membrane permeabilization. We show that LLOMe leads to hyperactivation of Rab7 (herein referring to Rab7a), and disruption of tubulation and mannose-6-phosphate receptor (CI-M6PR; also known as IGF2R) recycling on pH-neutralized LEs. pH neutralization (NH4Cl) and expression of Rab7 hyperactive mutants alone can both phenocopy the alterations in tubulation and CI-M6PR trafficking. Mechanistically, pH neutralization increases the assembly of the V1G1 subunit (encoded by ATP6V1G1) of the V-ATPase on endosomal membranes, which stabilizes GTP-bound Rab7 via RILP, a known interactor of Rab7 and V1G1. We propose a novel pathway by which V-ATPase and RILP modulate LE pH and Rab7 activation in concert. This pathway might broadly contribute to pH control during physiologic endosomal maturation or starvation and during pathologic pH neutralization, which occurs via lysosomotropic compounds and in disease states.
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Affiliation(s)
- Ryan J. Mulligan
- Department of Cell Biology, University of Virginia, Charlottesville, VA 22908, USA
- Cell and Developmental Biology Graduate Program, University of Virginia, Charlottesville, VA 22908, USA
- Medical Scientist Training Program, University of Virginia, Charlottesville, VA 22908, USA
| | - Magdalena M. Magaj
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA
- Cell and Developmental Biology Graduate Program, University of Virginia, Charlottesville, VA 22908, USA
| | - Laura Digilio
- Department of Cell Biology, University of Virginia, Charlottesville, VA 22908, USA
| | - Stefanie Redemann
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA 22908, USA
| | - Chan Choo Yap
- Department of Cell Biology, University of Virginia, Charlottesville, VA 22908, USA
| | - Bettina Winckler
- Department of Cell Biology, University of Virginia, Charlottesville, VA 22908, USA
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3
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Walia K, Sharma A, Paul S, Chouhan P, Kumar G, Ringe R, Sharma M, Tuli A. SARS-CoV-2 virulence factor ORF3a blocks lysosome function by modulating TBC1D5-dependent Rab7 GTPase cycle. Nat Commun 2024; 15:2053. [PMID: 38448435 PMCID: PMC10918171 DOI: 10.1038/s41467-024-46417-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Accepted: 02/26/2024] [Indexed: 03/08/2024] Open
Abstract
SARS-CoV-2, the causative agent of COVID-19, uses the host endolysosomal system for entry, replication, and egress. Previous studies have shown that the SARS-CoV-2 virulence factor ORF3a interacts with the lysosomal tethering factor HOPS complex and blocks HOPS-mediated late endosome and autophagosome fusion with lysosomes. Here, we report that SARS-CoV-2 infection leads to hyperactivation of the late endosomal and lysosomal small GTP-binding protein Rab7, which is dependent on ORF3a expression. We also observed Rab7 hyperactivation in naturally occurring ORF3a variants encoded by distinct SARS-CoV-2 variants. We found that ORF3a, in complex with Vps39, sequesters the Rab7 GAP TBC1D5 and displaces Rab7 from this complex. Thus, ORF3a disrupts the GTP hydrolysis cycle of Rab7, which is beneficial for viral production, whereas the Rab7 GDP-locked mutant strongly reduces viral replication. Hyperactivation of Rab7 in ORF3a-expressing cells impaired CI-M6PR retrieval from late endosomes to the trans-Golgi network, disrupting the biosynthetic transport of newly synthesized hydrolases to lysosomes. Furthermore, the tethering of the Rab7- and Arl8b-positive compartments was strikingly reduced upon ORF3a expression. As SARS-CoV-2 egress requires Arl8b, these findings suggest that ORF3a-mediated hyperactivation of Rab7 serves a multitude of functions, including blocking endolysosome formation, interrupting the transport of lysosomal hydrolases, and promoting viral egress.
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Affiliation(s)
- Kshitiz Walia
- Division of Cell Biology and Immunology, CSIR-Institute of Microbial Technology (IMTECH), Chandigarh, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, Uttar Pradesh, India
| | - Abhishek Sharma
- Division of Cell Biology and Immunology, CSIR-Institute of Microbial Technology (IMTECH), Chandigarh, India
| | - Sankalita Paul
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER), Mohali, Punjab, India
| | - Priya Chouhan
- Division of Cell Biology and Immunology, CSIR-Institute of Microbial Technology (IMTECH), Chandigarh, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, Uttar Pradesh, India
| | - Gaurav Kumar
- Division of Cell Biology and Immunology, CSIR-Institute of Microbial Technology (IMTECH), Chandigarh, India
| | - Rajesh Ringe
- Division of Cell Biology and Immunology, CSIR-Institute of Microbial Technology (IMTECH), Chandigarh, India
| | - Mahak Sharma
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER), Mohali, Punjab, India
| | - Amit Tuli
- Division of Cell Biology and Immunology, CSIR-Institute of Microbial Technology (IMTECH), Chandigarh, India.
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, Uttar Pradesh, India.
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4
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Mulligan R, Magaj M, Digilio L, Redemann S, Yap C, Winckler B. Collapse of late endosomal pH elicits a rapid Rab7 response via V-ATPase and RILP. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.10.24.563658. [PMID: 37961579 PMCID: PMC10634777 DOI: 10.1101/2023.10.24.563658] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
Endosomal-lysosomal trafficking is accompanied by the acidification of endosomal compartments by the H+-V-ATPase to reach low lysosomal pH. Disruption of proper pH impairs lysosomal function and the balance of protein synthesis and degradation (proteostasis). We used the small dipeptide LLOMe, which is known to permeabilize lysosomal membranes, and find that LLOMe also impacts late endosomes (LEs) by neutralizing their pH without causing membrane permeabilization. We show that LLOMe leads to hyper-activation of Rab7 and disruption of tubulation and mannose-6-phosphate receptor (CI-M6PR) recycling on pH-neutralized LEs. Either pH neutralization (NH4Cl) or Rab7 hyper-active mutants alone can phenocopy the alterations in tubulation and CI-M6PR trafficking. Mechanistically, pH neutralization increases the assembly of the V1G1 subunit of the V-ATPase on endosomal membranes, which stabilizes GTP-bound Rab7 via RILP, a known interactor of Rab7 and V1G1. We propose a novel pathway by which V-ATPase and RILP modulate LE pH and Rab7 activation in concert. This pathway might broadly contribute to pH control during physiologic endosomal maturation or starvation and during pathologic pH neutralization, which occurs via lysosomotropic compounds or in disease states.
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Affiliation(s)
- R.J. Mulligan
- Department of Cell Biology, University of Virginia, Charlottesville, VA
- Cell and Developmental Biology Graduate Program, University of Virginia, Charlottesville, VA
- Medical Scientist Training Program, University of Virginia, Charlottesville, VA
| | - M.M. Magaj
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville VA
- Cell and Developmental Biology Graduate Program, University of Virginia, Charlottesville, VA
| | - L. Digilio
- Department of Cell Biology, University of Virginia, Charlottesville, VA
| | - S. Redemann
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville VA
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA
| | - C.C. Yap
- Department of Cell Biology, University of Virginia, Charlottesville, VA
| | - B Winckler
- Department of Cell Biology, University of Virginia, Charlottesville, VA
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5
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Cottarelli A, Shahriar S, Arac A, Glendinning M, Tuohy MC, Prochilo G, Neal JB, Edinger AL, Agalliu D. Rab7a activation promotes degradation of select tight junction proteins at the blood-brain barrier after ischemic stroke. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.29.555373. [PMID: 37693406 PMCID: PMC10491261 DOI: 10.1101/2023.08.29.555373] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/12/2023]
Abstract
The stability of tight junctions (TJs) between endothelial cells (ECs) is essential to maintain blood-brain barrier (BBB) function in the healthy brain. Following ischemic stroke, TJ strand dismantlement due to protein degradation leads to BBB dysfunction, yet the mechanisms driving this process are poorly understood. Here, we show that endothelial-specific ablation of Rab7a, a small GTPase that regulates endolysosomal protein degradation, reduces stroke-induced TJ strand disassembly resulting in decreased paracellular BBB permeability and improved neuronal outcomes. Two pro-inflammatory cytokines, TNFα and IL1β, but not glucose and oxygen deprivation, induce Rab7a activation via Ccz1 in brain ECs in vitro, leading to increased TJ protein degradation and impaired paracellular barrier function. Silencing Rab7a in brain ECs in vitro reduces cytokine-driven endothelial barrier dysfunction by suppressing degradation of a key BBB TJ protein, Claudin-5. Thus, Rab7a activation by inflammatory cytokines promotes degradation of select TJ proteins leading to BBB dysfunction after ischemic stroke.
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Affiliation(s)
- Azzurra Cottarelli
- Departments of Neurology, Columbia University Irving Medical Center, New York, NY, 10032, USA
- Departments of Pathology and Cell Biology, Columbia University Irving Medical Center, New York, NY, 10032, USA
| | - Sanjid Shahriar
- Departments of Pathology and Cell Biology, Columbia University Irving Medical Center, New York, NY, 10032, USA
- Wyss Institute for Biologically Inspired Engineering, Boston, MA 02115, USA
| | - Ahmet Arac
- Department of Neurology, David Geffen School of Medicine, University of California in Los Angeles, Los Angeles, CA, 90095, USA
| | - Michael Glendinning
- Departments of Neurology, Columbia University Irving Medical Center, New York, NY, 10032, USA
| | - Mary Claire Tuohy
- Departments of Neurology, Columbia University Irving Medical Center, New York, NY, 10032, USA
| | - Grace Prochilo
- Departments of Neurology, Columbia University Irving Medical Center, New York, NY, 10032, USA
| | - Jason B. Neal
- Departments of Neurology, Columbia University Irving Medical Center, New York, NY, 10032, USA
- Baylor Scott and White Health, Dallas, TX, 75226, USA
| | - Aimee L. Edinger
- Departments of Developmental and Cell Biology and Pharmaceutical Sciences, University of California, Irvine, CA 92697, USA
| | - Dritan Agalliu
- Departments of Neurology, Columbia University Irving Medical Center, New York, NY, 10032, USA
- Departments of Pathology and Cell Biology, Columbia University Irving Medical Center, New York, NY, 10032, USA
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6
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Peng W, Schröder LF, Song P, Wong YC, Krainc D. Parkin regulates amino acid homeostasis at mitochondria-lysosome (M/L) contact sites in Parkinson's disease. SCIENCE ADVANCES 2023; 9:eadh3347. [PMID: 37467322 PMCID: PMC10355824 DOI: 10.1126/sciadv.adh3347] [Citation(s) in RCA: 14] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Accepted: 06/15/2023] [Indexed: 07/21/2023]
Abstract
Mutations in the E3 ubiquitin ligase parkin are the most common cause of early-onset Parkinson's disease (PD). Although parkin modulates mitochondrial and endolysosomal homeostasis during cellular stress, whether parkin regulates mitochondrial and lysosomal cross-talk under physiologic conditions remains unresolved. Using transcriptomics, metabolomics and super-resolution microscopy, we identify amino acid metabolism as a disrupted pathway in iPSC-derived dopaminergic neurons from patients with parkin PD. Compared to isogenic controls, parkin mutant neurons exhibit decreased mitochondria-lysosome contacts via destabilization of active Rab7. Subcellular metabolomics in parkin mutant neurons reveals amino acid accumulation in lysosomes and their deficiency in mitochondria. Knockdown of the Rab7 GTPase-activating protein TBC1D15 restores mitochondria-lysosome tethering and ameliorates cellular and subcellular amino acid profiles in parkin mutant neurons. Our data thus uncover a function of parkin in promoting mitochondrial and lysosomal amino acid homeostasis through stabilization of mitochondria-lysosome contacts and suggest that modulation of interorganelle contacts may serve as a potential target for ameliorating amino acid dyshomeostasis in disease.
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Affiliation(s)
| | - Leonie F. Schröder
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, USA
| | - Pingping Song
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, USA
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7
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Wong YC, Kim S, Cisneros J, Molakal CG, Song P, Lubbe SJ, Krainc D. Mid51/Fis1 mitochondrial oligomerization complex drives lysosomal untethering and network dynamics. J Cell Biol 2022; 221:213434. [PMID: 36044022 PMCID: PMC9437119 DOI: 10.1083/jcb.202206140] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 07/27/2022] [Accepted: 07/27/2022] [Indexed: 11/22/2022] Open
Abstract
Lysosomes are highly dynamic organelles implicated in multiple diseases. Using live super-resolution microscopy, we found that lysosomal tethering events rarely undergo lysosomal fusion, but rather untether over time to reorganize the lysosomal network. Inter-lysosomal untethering events are driven by a mitochondrial Mid51/Fis1 complex that undergoes coupled oligomerization on the outer mitochondrial membrane. Importantly, Fis1 oligomerization mediates TBC1D15 (Rab7-GAP) mitochondrial recruitment to drive inter-lysosomal untethering via Rab7 GTP hydrolysis. Moreover, inhibiting Fis1 oligomerization by either mutant Fis1 or a Mid51 oligomerization mutant potentially associated with Parkinson’s disease prevents lysosomal untethering events, resulting in misregulated lysosomal network dynamics. In contrast, dominant optic atrophy–linked mutant Mid51, which does not inhibit Mid51/Fis1 coupled oligomerization, does not disrupt downstream lysosomal dynamics. As Fis1 conversely also regulates Mid51 oligomerization, our work further highlights an oligomeric Mid51/Fis1 mitochondrial complex that mechanistically couples together both Drp1 and Rab7 GTP hydrolysis machinery at mitochondria–lysosome contact sites. These findings have significant implications for organelle networks in cellular homeostasis and human disease.
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Affiliation(s)
- Yvette C Wong
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL
| | - Soojin Kim
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL
| | - Jasmine Cisneros
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL
| | - Catherine G Molakal
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL
| | - Pingping Song
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL
| | - Steven J Lubbe
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL.,Simpson Querrey Center for Neurogenetics, Northwestern University Feinberg School of Medicine, Chicago, IL
| | - Dimitri Krainc
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL.,Simpson Querrey Center for Neurogenetics, Northwestern University Feinberg School of Medicine, Chicago, IL
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8
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Kim S, Wong YC, Gao F, Krainc D. Dysregulation of mitochondria-lysosome contacts by GBA1 dysfunction in dopaminergic neuronal models of Parkinson's disease. Nat Commun 2021; 12:1807. [PMID: 33753743 PMCID: PMC7985376 DOI: 10.1038/s41467-021-22113-3] [Citation(s) in RCA: 86] [Impact Index Per Article: 28.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Accepted: 02/16/2021] [Indexed: 12/20/2022] Open
Abstract
Mitochondria-lysosome contacts are recently identified sites for mediating crosstalk between both organelles, but their role in normal and diseased human neurons remains unknown. In this study, we demonstrate that mitochondria-lysosome contacts can dynamically form in the soma, axons, and dendrites of human neurons, allowing for their bidirectional crosstalk. Parkinson's disease patient derived neurons harboring mutant GBA1 exhibited prolonged mitochondria-lysosome contacts due to defective modulation of the untethering protein TBC1D15, which mediates Rab7 GTP hydrolysis for contact untethering. This dysregulation was due to decreased GBA1 (β-glucocerebrosidase (GCase)) lysosomal enzyme activity in patient derived neurons, and could be rescued by increasing enzyme activity with a GCase modulator. These defects resulted in disrupted mitochondrial distribution and function, and could be further rescued by TBC1D15 in Parkinson's patient derived GBA1-linked neurons. Together, our work demonstrates a potential role of mitochondria-lysosome contacts as an upstream regulator of mitochondrial function and dynamics in midbrain dopaminergic neurons in GBA1-linked Parkinson's disease.
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Affiliation(s)
- Soojin Kim
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Yvette C Wong
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Fanding Gao
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Dimitri Krainc
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.
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9
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Tong SJ, Lucas RM, Xiao Z, Luo L, Stow JL. Detecting Endogenous Rab8 Activation. Methods Mol Biol 2021; 2293:45-56. [PMID: 34453709 DOI: 10.1007/978-1-0716-1346-7_4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The family of Rab GTPases switch between GDP- and GTP-bound forms to interact with effectors and accessory proteins for the regulation of trafficking and signaling pathways in cells. The activation and recruitment of a specific Rab by stimulants or physiological changes can be detected and assessed by measuring the relative amount of the Rab in its active, "GTP-bound" state versus the inactive "GDP-bound" state. While GTP loading can be measured in vitro, current methods to detect the activation state of endogenous Rabs within a cellular context are limited. Here, we developed two molecular probes, based on domains of known Rab effectors, which can be used to pull down endogenous GTP-bound Rab8 from cell extracts as a measure of Rab8 activation. As a test system, we use the lipopolysaccharide (LPS) induced activation of Rab8 in mouse macrophages. The molecular probes compared for capture of GTP-bound Rab8 are derived from two Rab8 effectors, OCRL and PI3Kγ, with the former assessed as being more efficient. We describe how the OCRL-RBD probe is used to assess activation of Rab8 in cell extracts with a method that should be applicable to assessing GTP-bound Rab8 in other cell and tissue extracts.
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Affiliation(s)
- Samuel J Tong
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
| | - Richard M Lucas
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
| | - Zhijian Xiao
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
| | - Lin Luo
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia.
| | - Jennifer L Stow
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia.
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10
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Lin J, Zhuo Y, Yin Y, Qiu L, Li X, Lai F. Methylation of RILP in lung cancer promotes tumor cell proliferation and invasion. Mol Cell Biochem 2020; 476:853-861. [PMID: 33128214 DOI: 10.1007/s11010-020-03950-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Accepted: 10/14/2020] [Indexed: 12/19/2022]
Abstract
Rab-interacting lysosomal protein (RILP) has been suggested to perform as a tumor suppressor in breast and prostate cancer cell lines. However, its expression profile and functional role in lung cancer have never been investigated. We applied the well-established cancer genomic database-The Cancer Genome Atlas to compare the RILP expression and methylation between lung cancer tissues and normal tissues. The potential correlation of RILP with clinical characteristics of lung cancer patients (e.g., stages, smoking, TP53, and methylation) was also be explored. Our results showed that the downregulation of RILP and upregulation of RILP methylation were identified in lung cancer tissues compared to normal healthy tissues. Downregulation of RILP was positively associated with lung cancer later stage (N3), smoking history, TP53 mutation, and poor prognosis, as well as inversely correlated with DNA (cytosine-5)-methyltransferase 1 (DNMT1) expression. Demethylation treatment enhanced RILP expression in lung cancer cells, suggesting hypermethylation is responsible for RILP silencing in lung cancer. We further found that RILP depletion promoted lung cancer cell proliferation, migration, and invasion. We concluded that RILP acts as a tumor suppressor in lung cancer cells. Our results provided the theoretical basis for developing RILP-targeting or demethylating agents for lung cancer treatment.
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Affiliation(s)
- Jianbo Lin
- Department of Thoracic Surgery, the First Affiliated Hospital of Fujian Medical University, No. 20 Chazhong Road, Fuzhou, 350005, Fujian, China
| | - Yi Zhuo
- Department of Thoracic Surgery, the First Affiliated Hospital of Fujian Medical University, No. 20 Chazhong Road, Fuzhou, 350005, Fujian, China
| | - Yinhe Yin
- Department of Thoracic Surgery, the First Affiliated Hospital of Fujian Medical University, No. 20 Chazhong Road, Fuzhou, 350005, Fujian, China
| | - Linbin Qiu
- Department of Thoracic Surgery, the First Affiliated Hospital of Fujian Medical University, No. 20 Chazhong Road, Fuzhou, 350005, Fujian, China
| | - Xu Li
- Department of Thoracic Surgery, the First Affiliated Hospital of Fujian Medical University, No. 20 Chazhong Road, Fuzhou, 350005, Fujian, China
| | - Fancai Lai
- Department of Thoracic Surgery, the First Affiliated Hospital of Fujian Medical University, No. 20 Chazhong Road, Fuzhou, 350005, Fujian, China.
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11
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Cellular Prion Protein (PrPc): Putative Interacting Partners and Consequences of the Interaction. Int J Mol Sci 2020; 21:ijms21197058. [PMID: 32992764 PMCID: PMC7583789 DOI: 10.3390/ijms21197058] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 09/20/2020] [Accepted: 09/23/2020] [Indexed: 02/08/2023] Open
Abstract
Cellular prion protein (PrPc) is a small glycosylphosphatidylinositol (GPI) anchored protein most abundantly found in the outer leaflet of the plasma membrane (PM) in the central nervous system (CNS). PrPc misfolding causes neurodegenerative prion diseases in the CNS. PrPc interacts with a wide range of protein partners because of the intrinsically disordered nature of the protein’s N-terminus. Numerous studies have attempted to decipher the physiological role of the prion protein by searching for proteins which interact with PrPc. Biochemical characteristics and biological functions both appear to be affected by interacting protein partners. The key challenge in identifying a potential interacting partner is to demonstrate that binding to a specific ligand is necessary for cellular physiological function or malfunction. In this review, we have summarized the intracellular and extracellular interacting partners of PrPc and potential consequences of their binding. We also briefly describe prion disease-related mutations at the end of this review.
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12
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Modulation of Rab7a-mediated growth factor receptor trafficking inhibits islet beta cell apoptosis and autophagy under conditions of metabolic stress. Sci Rep 2020; 10:15741. [PMID: 32978479 PMCID: PMC7519639 DOI: 10.1038/s41598-020-72939-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Accepted: 09/09/2020] [Indexed: 01/01/2023] Open
Abstract
Regenerative medicine approaches to enhancing beta cell growth and survival represent potential treatments for diabetes. It is known that growth factors such as insulin, IGF-1 and HGF support beta cell growth and survival, but in people with type 2 diabetes the destructive effects of metabolic stress predominate and beta cell death or dysfunction occurs. In this study we explore the novel hypothesis that regulation of growth factor receptor trafficking can be used to promote islet beta cell survival. Growth factor signalling is dependent on the presence of cell surface receptors. Endosomal trafficking and subsequent recycling or degradation of these receptors is controlled by the Rab GTPase family of proteins. We show that Rab7a siRNA inhibition enhances IGF-1 and HGF signalling in beta cells and increases expression of the growth factor receptors IGF-1R and c-Met. Furthermore, Rab7a inhibition promotes beta cell growth and islet survival, and protects against activation of apoptosis and autophagy pathways under conditions of metabolic stress. This study therefore demonstrates that Rab7a-mediated trafficking of growth factor receptors controls beta cell survival. Pharmaceutical Rab7a inhibition may provide a means to promote beta cell survival in the context of metabolic stress and prevent the onset of type 2 diabetes.
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Cai CZ, Yang C, Zhuang XX, Yuan NN, Wu MY, Tan JQ, Song JX, Cheung KH, Su H, Wang YT, Tang BS, Behrends C, Durairajan SSK, Yue Z, Li M, Lu JH. NRBF2 is a RAB7 effector required for autophagosome maturation and mediates the association of APP-CTFs with active form of RAB7 for degradation. Autophagy 2020; 17:1112-1130. [PMID: 32543313 DOI: 10.1080/15548627.2020.1760623] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
NRBF2 is a component of the class III phosphatidylinositol 3-kinase (PtdIns3K) complex. Our previous study has revealed its role in regulating ATG14-associated PtdIns3K activity for autophagosome initiation. In this study, we revealed an unknown mechanism by which NRBF2 modulates autophagosome maturation and APP-C-terminal fragment (CTF) degradation. Our data showed that NRBF2 localized at autolysosomes, and loss of NRBF2 impaired autophagosome maturation. Mechanistically, NRBF2 colocalizes with RAB7 and is required for generation of GTP-bound RAB7 by interacting with RAB7 GEF CCZ1-MON1A and maintaining the GEF activity. Specifically, NRBF2 regulates CCZ1-MON1A interaction with PI3KC3/VPS34 and CCZ1-associated PI3KC3 kinase activity, which are required for CCZ1-MON1A GEF activity. Finally, we showed that NRBF2 is involved in APP-CTF degradation and amyloid beta peptide production by maintaining the interaction between APP and the CCZ1-MON1A-RAB7 module to facilitate the maturation of APP-containing vesicles. Overall, our study revealed a pivotal role of NRBF2 as a new RAB7 effector in modulating autophagosome maturation, providing insight into the molecular mechanism of NRBF2-PtdIns3K in regulating RAB7 activity for macroautophagy/autophagy maturation and Alzheimer disease-associated protein degradation..Abbreviations: 3xTg AD, triple transgenic mouse for Alzheimer disease; Aβ, amyloid beta peptide; Aβ1-40, amyloid beta peptide 1-40; Aβ1-42, amyloid beta peptide 1-42; AD, Alzheimer disease; APP, amyloid beta precursor protein; APP-CTFs, APP C-terminal fragments; ATG, autophagy related; ATG5, autophagy related 5; ATG7, autophagy related 7; ATG14, autophagy related 14; CCD, coiled-coil domain; CCZ1, CCZ1 homolog, vacuolar protein trafficking and biogenesis associated; CHX, cycloheximide; CQ, chloroquine; DAPI, 4',6-diamidino-2-phenylindole; dCCD, delete CCD; dMIT, delete MIT; FYCO1, FYVE and coiled-coil domain autophagy adaptor 1; FYVE, Fab1, YGL023, Vps27, and EEA1; GAP, GTPase-activating protein; GDP, guanine diphosphate; GEF, guanine nucleotide exchange factor; GTP, guanine triphosphate; GTPase, guanosine triphosphatase; HOPS, homotypic fusion and vacuole protein sorting; ILVs, endosomal intralumenal vesicles; KD, knockdown; KO, knockout; LAMP1, lysosomal associated membrane protein 1; MAP1LC3/LC3, microtubule associated protein 1 light chain 3; MLVs, multilamellar vesicles; MON1A, MON1 homolog A, secretory trafficking associated; NRBF2, nuclear receptor binding factor 2; PtdIns3K, class III phosphatidylinositol 3-kinase; PtdIns3P, phosphatidylinositol-3-phosphate; RILP, Rab interacting lysosomal protein; SNARE, soluble N-ethylmaleimide-sensitive factor attachment protein receptor; SQSTM1/p62, sequestosome 1; UVRAG, UV radiation resistance associated; VPS, vacuolar protein sorting; WT, wild type.
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Affiliation(s)
- Cui-Zan Cai
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Macau SAR, China
| | - Chuanbin Yang
- Mr. And Mrs. Ko Chi Ming Centre for Parkinson's Disease Research, School of Chinese Medicine, Hong Kong Baptist University, Hong Kong SAR, China
| | - Xu-Xu Zhuang
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Macau SAR, China
| | - Ning-Ning Yuan
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Macau SAR, China
| | - Ming-Yue Wu
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Macau SAR, China
| | - Jie-Qiong Tan
- Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Ju-Xian Song
- Mr. And Mrs. Ko Chi Ming Centre for Parkinson's Disease Research, School of Chinese Medicine, Hong Kong Baptist University, Hong Kong SAR, China.,Medical College of Acupuncture-Moxibustion and Rehabilitation, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - King-Ho Cheung
- Mr. And Mrs. Ko Chi Ming Centre for Parkinson's Disease Research, School of Chinese Medicine, Hong Kong Baptist University, Hong Kong SAR, China
| | - Huanxing Su
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Macau SAR, China
| | - Yi-Tao Wang
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Macau SAR, China
| | - Bei-Sha Tang
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Christian Behrends
- Munich Cluster for Systems Neurology (Synergy), Ludwig-Maximilians-Universität München, München, Germany
| | - Siva Sundara Kumar Durairajan
- Mr. And Mrs. Ko Chi Ming Centre for Parkinson's Disease Research, School of Chinese Medicine, Hong Kong Baptist University, Hong Kong SAR, China.,Division of Mycobiology and Neurodegenerative Disease Research, Department of Microbiology, School of Life Sciences, Central University of Tamil Nadu, Tiruvarur, India
| | - Zhenyu Yue
- Department of Neurology and Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Min Li
- Mr. And Mrs. Ko Chi Ming Centre for Parkinson's Disease Research, School of Chinese Medicine, Hong Kong Baptist University, Hong Kong SAR, China
| | - Jia-Hong Lu
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Macau SAR, China
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14
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Guerra F, Bucci C. Role of the RAB7 Protein in Tumor Progression and Cisplatin Chemoresistance. Cancers (Basel) 2019; 11:cancers11081096. [PMID: 31374919 PMCID: PMC6721790 DOI: 10.3390/cancers11081096] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Revised: 07/23/2019] [Accepted: 07/30/2019] [Indexed: 12/19/2022] Open
Abstract
RAB7 is a small guanosine triphosphatase (GTPase) extensively studied as regulator of vesicular trafficking. Indeed, its role is fundamental in several steps of the late endocytic pathway, including endosome maturation, transport from early endosomes to late endosomes and lysosomes, clustering and fusion of late endosomes and lysosomes in the perinuclear region and lysosomal biogenesis. Besides endocytosis, RAB7 is important for a number of other cellular processes among which, autophagy, apoptosis, signaling, and cell migration. Given the importance of RAB7 in these cellular processes, the interest to study the role of RAB7 in cancer progression is widely grown. Here, we describe the current understanding of oncogenic and oncosuppressor functions of RAB7 analyzing cellular context and other environmental factors in which it elicits pro and/or antitumorigenic effects. We also discuss the role of RAB7 in cisplatin resistance associated with its ability to regulate the late endosomal pathway, lysosomal biogenesis and extracellular vesicle secretion. Finally, we examined the potential cancer therapeutic strategies targeting the different molecular events in which RAB7 is involved.
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Affiliation(s)
- Flora Guerra
- Department of Biological and Environmental Sciences and Technologies (DiSTeBA), University of Salento, Via Provinciale Lecce-Monteroni 165, 73100 Lecce, Italy.
| | - Cecilia Bucci
- Department of Biological and Environmental Sciences and Technologies (DiSTeBA), University of Salento, Via Provinciale Lecce-Monteroni 165, 73100 Lecce, Italy.
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15
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Wong YC, Peng W, Krainc D. Lysosomal Regulation of Inter-mitochondrial Contact Fate and Motility in Charcot-Marie-Tooth Type 2. Dev Cell 2019; 50:339-354.e4. [PMID: 31231042 DOI: 10.1016/j.devcel.2019.05.033] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Revised: 02/25/2019] [Accepted: 05/16/2019] [Indexed: 10/26/2022]
Abstract
Properly regulated mitochondrial networks are essential for cellular function and implicated in multiple diseases. Mitochondria undergo fission and fusion events, but the dynamics and regulation of a third event of inter-mitochondrial contact formation remain unclear. Using super-resolution imaging, we demonstrate that inter-mitochondrial contacts frequently form and play a fundamental role in mitochondrial networks by restricting mitochondrial motility. Inter-mitochondrial contact untethering events are marked and regulated by mitochondria-lysosome contacts, which are modulated by RAB7 GTP hydrolysis. Moreover, inter-mitochondrial contact formation and untethering are further regulated by Mfn1/2 and Drp1 GTP hydrolysis, respectively. Surprisingly, endoplasmic reticulum tubules are also present at inter-mitochondrial contact untethering events, in addition to mitochondrial fission and fusion events. Importantly, we find that multiple Charcot-Marie-Tooth type 2 disease-linked mutations in Mfn2 (CMT2A), RAB7 (CMT2B), and TRPV4 (CMT2C) converge on prolonged inter-mitochondrial contacts and defective mitochondrial motility, highlighting a role for inter-mitochondrial contacts in mitochondrial network regulation and disease.
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Affiliation(s)
- Yvette C Wong
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Wesley Peng
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Dimitri Krainc
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA.
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16
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Baba T, Toth DJ, Sengupta N, Kim YJ, Balla T. Phosphatidylinositol 4,5-bisphosphate controls Rab7 and PLEKHM1 membrane cycling during autophagosome-lysosome fusion. EMBO J 2019; 38:e100312. [PMID: 31368593 PMCID: PMC6463214 DOI: 10.15252/embj.2018100312] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Revised: 01/02/2019] [Accepted: 01/23/2019] [Indexed: 12/12/2022] Open
Abstract
The small GTPase Rab7 is a key organizer of receptor sorting and lysosomal degradation by recruiting of a variety of effectors depending on its GDP/GTP-bound state. However, molecular mechanisms that trigger Rab7 inactivation remain elusive. Here we find that, among the endosomal pools, Rab7-positive compartments possess the highest level of PI4P, which is primarily produced by PI4K2A kinase. Acute conversion of this endosomal PI4P to PI(4,5)P2 causes Rab7 dissociation from late endosomes and releases a regulator of autophagosome-lysosome fusion, PLEKHM1, from the membrane. Rab7 effectors Vps35 and RILP are not affected by acute PI(4,5)P2 production. Deletion of PI4K2A greatly reduces PIP5Kγ-mediated PI(4,5)P2 production in Rab7-positive endosomes leading to impaired Rab7 inactivation and increased number of LC3-positive structures with defective autophagosome-lysosome fusion. These results reveal a late endosomal PI4P-PI(4,5)P2 -dependent regulatory loop that impacts autophagosome flux by affecting Rab7 cycling and PLEKHM1 association.
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Affiliation(s)
- Takashi Baba
- Section on Molecular Signal TransductionProgram for Developmental NeuroscienceEunice Kennedy Shriver National Institute of Child Health and Human DevelopmentNational Institutes of HealthBethesdaMDUSA
| | - Daniel J Toth
- Section on Molecular Signal TransductionProgram for Developmental NeuroscienceEunice Kennedy Shriver National Institute of Child Health and Human DevelopmentNational Institutes of HealthBethesdaMDUSA
| | - Nivedita Sengupta
- Section on Molecular Signal TransductionProgram for Developmental NeuroscienceEunice Kennedy Shriver National Institute of Child Health and Human DevelopmentNational Institutes of HealthBethesdaMDUSA
| | - Yeun Ju Kim
- Section on Molecular Signal TransductionProgram for Developmental NeuroscienceEunice Kennedy Shriver National Institute of Child Health and Human DevelopmentNational Institutes of HealthBethesdaMDUSA
| | - Tamas Balla
- Section on Molecular Signal TransductionProgram for Developmental NeuroscienceEunice Kennedy Shriver National Institute of Child Health and Human DevelopmentNational Institutes of HealthBethesdaMDUSA
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17
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Proton pumping V-ATPase inhibitor bafilomycin A1 affects Rab7 lysosomal localization and abolishes anterograde trafficking of osteoclast secretory lysosomes. Biochem Biophys Res Commun 2019; 510:421-426. [DOI: 10.1016/j.bbrc.2019.01.118] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Accepted: 01/26/2019] [Indexed: 01/03/2023]
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18
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Mohapatra G, Gaur P, Mujagond P, Singh M, Rana S, Pratap S, Kaur N, Verma S, Krishnan V, Singh N, Srikanth CV. A SUMOylation-dependent switch of RAB7 governs intracellular life and pathogenesis of Salmonella Typhimurium. J Cell Sci 2019; 132:jcs.222612. [PMID: 30510112 DOI: 10.1242/jcs.222612] [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: 07/13/2018] [Accepted: 11/26/2018] [Indexed: 01/06/2023] Open
Abstract
Salmonella Typhimurium is an intracellular pathogen that causes gastroenteritis in humans. Aided by a battery of effector proteins, S. Typhimurium resides intracellularly in a specialized vesicle, called the Salmonella-containing vacuole (SCV) that utilizes the host endocytic vesicular transport pathway (VTP). Here, we probed the possible role of SUMOylation, a post-translation modification pathway, in SCV biology. Proteome analysis by complex mass-spectrometry (MS/MS) revealed a dramatically altered SUMO-proteome (SUMOylome) in S. Typhimurium-infected cells. RAB7, a component of VTP, was key among several crucial proteins identified in our study. Detailed MS/MS assays, in vitro SUMOylation assays and structural docking analysis revealed SUMOylation of RAB7 (RAB7A) specifically at lysine 175. A SUMOylation-deficient RAB7 mutant (RAB7K175R) displayed longer half-life, was beneficial to SCV dynamics and functionally deficient. Collectively, the data revealed that RAB7 SUMOylation blockade by S. Typhimurium ensures availability of long-lived but functionally compromised RAB7, which was beneficial to the pathogen. Overall, this SUMOylation-dependent switch of RAB7 controlled by S. Typhimurium is an unexpected mode of VTP pathway regulation, and unveils a mechanism of broad interest well beyond Salmonella-host crosstalk. This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Gayatree Mohapatra
- Laboratory of Gut Inflammation and Infection Biology, Regional Centre for Biotechnology NCR Biotech Science Cluster 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad - 121 001 Haryana (NCR Delhi), India.,Manipal Acadamy of Higher Education, Manipal, Karnataka 576104, India
| | - Preksha Gaur
- Laboratory of Gut Inflammation and Infection Biology, Regional Centre for Biotechnology NCR Biotech Science Cluster 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad - 121 001 Haryana (NCR Delhi), India
| | - Prabhakar Mujagond
- Laboratory of Gut Inflammation and Infection Biology, Regional Centre for Biotechnology NCR Biotech Science Cluster 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad - 121 001 Haryana (NCR Delhi), India
| | - Mukesh Singh
- Pediatric Biology Centre, Translational Health Science and Technology Institute, NCR Biotech Science Cluster, 3rd Milestone, Faridabad - Gurgaon Expressway, PO box #04, Faridabad - 121001 Haryana, India
| | - Sarika Rana
- Laboratory of Gut Inflammation and Infection Biology, Regional Centre for Biotechnology NCR Biotech Science Cluster 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad - 121 001 Haryana (NCR Delhi), India.,Manipal Acadamy of Higher Education, Manipal, Karnataka 576104, India
| | - Shivendra Pratap
- Laboratory of Gut Inflammation and Infection Biology, Regional Centre for Biotechnology NCR Biotech Science Cluster 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad - 121 001 Haryana (NCR Delhi), India
| | - Navneet Kaur
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Centre, Omaha, NE 68198, USA
| | - Smriti Verma
- Mucosal Immunology and Biology Research Center, Massachusetts General Hospital, Building 114, 16th Street, Charlestown, MA 02129, USA
| | - Vengadesan Krishnan
- Laboratory of Gut Inflammation and Infection Biology, Regional Centre for Biotechnology NCR Biotech Science Cluster 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad - 121 001 Haryana (NCR Delhi), India
| | - Nirpendra Singh
- Laboratory of Gut Inflammation and Infection Biology, Regional Centre for Biotechnology NCR Biotech Science Cluster 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad - 121 001 Haryana (NCR Delhi), India
| | - C V Srikanth
- Laboratory of Gut Inflammation and Infection Biology, Regional Centre for Biotechnology NCR Biotech Science Cluster 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad - 121 001 Haryana (NCR Delhi), India
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19
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Abstract
While cancer cell proliferation depends on access to extracellular nutrients, inadequate tumour perfusion means that glucose, amino acids and lipids are often in short supply. To overcome this obstacle to growth, cancer cells utilize multiple scavenging strategies, obtaining macromolecules from the microenvironment and breaking them down in the lysosome to produce substrates for ATP generation and anabolism. Recent studies have revealed four scavenging pathways that support cancer cell proliferation in low-nutrient environments: scavenging of extracellular matrix proteins via integrins, receptor-mediated albumin uptake and catabolism, macropinocytic consumption of multiple components of the tumour microenvironment and the engulfment and degradation of entire live cells via entosis. New evidence suggests that blocking these pathways alone or in combination could provide substantial benefits to patients with incurable solid tumours. Both US Food and Drug Administration (FDA)-approved drugs and several agents in preclinical or clinical development shut down individual or multiple scavenging pathways. These therapies may increase the extent and durability of tumour growth inhibition and/or prevent the development of resistance when used in combination with existing treatments. This Review summarizes the evidence suggesting that scavenging pathways drive tumour growth, highlights recent advances that define the oncogenic signal transduction pathways that regulate scavenging and considers the benefits and detriments of therapeutic strategies targeting scavenging that are currently under development.
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Affiliation(s)
- Brendan T Finicle
- Department of Developmental and Cell Biology, University of California Irvine, Irvine, CA, USA
| | - Vaishali Jayashankar
- Department of Developmental and Cell Biology, University of California Irvine, Irvine, CA, USA
| | - Aimee L Edinger
- Department of Developmental and Cell Biology, University of California Irvine, Irvine, CA, USA.
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20
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Court H, Ahearn IM, Amoyel M, Bach EA, Philips MR. Regulation of NOTCH signaling by RAB7 and RAB8 requires carboxyl methylation by ICMT. J Cell Biol 2017; 216:4165-4182. [PMID: 29051265 PMCID: PMC5716267 DOI: 10.1083/jcb.201701053] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Revised: 08/04/2017] [Accepted: 09/12/2017] [Indexed: 01/15/2023] Open
Abstract
Isoprenylcysteine carboxyl methyltransferase (ICMT) methylesterifies C-terminal prenylcysteine residues of CaaX proteins and some RAB GTPases. Deficiency of either ICMT or NOTCH1 accelerates pancreatic neoplasia in Pdx1-Cre;LSL-KrasG12D mice, suggesting that ICMT is required for NOTCH signaling. We used Drosophila melanogaster wing vein and scutellar bristle development to screen Rab proteins predicted to be substrates for ICMT (ste14 in flies). We identified Rab7 and Rab8 as ICMT substrates that when silenced phenocopy ste14 deficiency. ICMT, RAB7, and RAB8 were all required for efficient NOTCH1 signaling in mammalian cells. Overexpression of RAB8 rescued NOTCH activation after ICMT knockdown both in U2OS cells expressing NOTCH1 and in fly wing vein development. ICMT deficiency induced mislocalization of GFP-RAB7 and GFP-RAB8 from endomembrane to cytosol, enhanced binding to RABGDI, and decreased GTP loading of RAB7 and RAB8. Deficiency of ICMT, RAB7, or RAB8 led to mislocalization and diminished processing of NOTCH1-GFP. Thus, NOTCH signaling requires ICMT in part because it requires methylated RAB7 and RAB8.
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Affiliation(s)
- Helen Court
- Perlmutter Cancer Center, New York University School of Medicine, New York, NY
| | - Ian M Ahearn
- Perlmutter Cancer Center, New York University School of Medicine, New York, NY
| | - Marc Amoyel
- School of Cellular and Molecular Medicine, University of Bristol, Bristol, England, UK
| | - Erika A Bach
- Perlmutter Cancer Center, New York University School of Medicine, New York, NY
| | - Mark R Philips
- Perlmutter Cancer Center, New York University School of Medicine, New York, NY
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21
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Timely regulated sorting from early to late endosomes is required to maintain cerebellar long-term depression. Nat Commun 2017; 8:401. [PMID: 28864821 PMCID: PMC5581341 DOI: 10.1038/s41467-017-00518-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Accepted: 07/05/2017] [Indexed: 11/16/2022] Open
Abstract
An important feature of long-term synaptic plasticity is the prolonged maintenance of plastic changes in synaptic transmission. The trafficking of AMPA-type glutamate receptors (AMPARs) is involved in the expression of many forms of synaptic plasticity, yet the subsequent events accomplishing the maintenance of plastic changes in synaptic AMPAR numbers are not fully understood. Here, we find that maintenance of cerebellar long-term depression results from a reduction in the number of AMPARs residing within endocytic recycling pathways. We then develop a genetically encoded, photosensitive inhibitor of late endosome sorting and use this to discover that initial maintenance of long-term depression relies on timely regulated late endosome sorting, which exhibits a threshold as well as switch-like behavior. Thus, our results indicate that recycling AMPAR numbers are reduced by a switching machinery of transient late endosome sorting, and that this process enables the transition from basal synaptic transmission to long-term depression maintenance. Long term depression (LTD) of the cerebellum is known to be mediated by postsynaptic trafficking of glutamate receptor AMPAR. Here, Kim and colleagues show that early- to late-endosomal sorting of AMPAR represents the switch from expression to maintenance phase of cerebellar LTD.
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22
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Internalized CD44s splice isoform attenuates EGFR degradation by targeting Rab7A. Proc Natl Acad Sci U S A 2017; 114:8366-8371. [PMID: 28716909 DOI: 10.1073/pnas.1701289114] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
CD44 has been postulated as a cell surface coreceptor for augmenting receptor tyrosine kinase (RTK) signaling. However, how exactly CD44 triggers RTK-dependent signaling remained largely unclear. Here we report an unexpected mechanism by which the CD44s splice isoform is internalized into endosomes to attenuate EGFR degradation. We identify a CD44s-interacting small GTPase, Rab7A, and show that CD44s inhibits Rab7A-mediated EGFR trafficking to lysosomes and subsequent degradation. Importantly, CD44s levels correlate with EGFR signature and predict poor prognosis in glioblastomas. Because Rab7A facilitates trafficking of many RTKs to lysosomes, our findings identify CD44s as a Rab7A regulator to attenuate RTK degradation.
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23
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Tripathy MK, Tiwari BS, Reddy MK, Deswal R, Sopory SK. Ectopic expression of PgRab7 in rice plants (Oryza sativa L.) results in differential tolerance at the vegetative and seed setting stage during salinity and drought stress. PROTOPLASMA 2017; 254:109-124. [PMID: 26666551 DOI: 10.1007/s00709-015-0914-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2015] [Accepted: 11/19/2015] [Indexed: 05/23/2023]
Abstract
In this work, we have overexpressed a vesicle trafficking protein, Rab7, from a stress-tolerant plant, Pennisetum glaucum, in a high-yielding but stress-sensitive rice variety Pusa Basmati-1 (PB-1). The transgenic rice plants were tested for tolerance against salinity and drought stress. The transgenic plants showed considerable tolerance at the vegetative stage against both salinity (200 mM NaCl) and drought stress (up to 12 days after withdrawing water). The protection against salt and drought stress may be by regulating Na+ ion homeostasis, as the transgenic plants showed altered expression of multiple transporter genes, including OsNHX1, OsNHX2, OsSOS1, OsVHA, and OsGLRs. In addition, decreased generation and maintenance of lesser reactive oxygen species (ROS), with maintenance of chloroplast grana and photosynthetic machinery was observed. When evaluated for reproductive growth, 89-96 % of seed setting was maintained in transgenic plants during drought stress; however, under salt stress, a 33-53 % decrease in seed setting was observed. These results indicate that PgRab7 overexpression in rice confers differential tolerance at the seed setting stage during salinity and drought stress and could be a favored target for raising drought-tolerant crops.
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Affiliation(s)
- Manas Kumar Tripathy
- Plant Molecular Biology Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi, 110067, India.
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX, 78712, USA.
| | - Budhi Sagar Tiwari
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, 110067, India
| | - Malireddy K Reddy
- Plant Molecular Biology Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi, 110067, India
| | - Renu Deswal
- Department of Botany, University of Delhi, Delhi, 110007, India
| | - Sudhir K Sopory
- Plant Molecular Biology Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi, 110067, India.
- Jawaharlal Nehru University, New Delhi, 110067, India.
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Margiotta A, Progida C, Bakke O, Bucci C. Rab7a regulates cell migration through Rac1 and vimentin. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2016; 1864:367-381. [PMID: 27888097 DOI: 10.1016/j.bbamcr.2016.11.020] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2016] [Revised: 11/09/2016] [Accepted: 11/19/2016] [Indexed: 01/17/2023]
Abstract
Rab7a, a small GTPase of the Rab family, is localized to late endosomes and controls late endocytic trafficking. The discovery of several Rab7a interacting proteins revealed that Rab7a function is closely connected to cytoskeletal elements. Indeed, Rab7a recruits on vesicles RILP and FYCO that are responsible for the movement of Rab7a-positive vesicles and/or organelles on microtubule tracks, but also directly interacts with Rac1, a fundamental regulator of actin cytoskeleton, and with peripherin and vimentin, two intermediate filament proteins. Considering all these interactions and, in particular, the fact that Rac1 and vimentin are key factors for cellular motility, we investigated a possible role of Rab7a in cell migration. We show here that Rab7a is needed for cell migration as Rab7a depletion causes slower migration of NCI H1299 cells affecting cell velocity and directness. Rab7a depletion negatively affects adhesion and spreading onto fibronectin substrates, altering β1-integrin activation, localization and intracellular trafficking, and myosin X localization. In fact, Rab7a-depleted cells show 40% less filopodia and active integrin accumulates at the leading edge of migrating cells. Furthermore, Rab7a depletion decreases the amount of active Rac1 but not its abundance and reduces the number of cells with vimentin filaments facing the wound, indicating that Rab7a has a role in the orientation of vimentin filaments during migration. In conclusion, our results demonstrate a key role of Rab7a in the regulation of different aspects of cell migration.
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Affiliation(s)
- Azzurra Margiotta
- Department of Biological and Environmental Sciences and Technologies, (DiSTeBA) University of Salento, Via Provinciale Monteroni 165, 73100 Lecce, Italy; Department of Biosciences, Centre for Immune Regulation, University of Oslo, Blindernveien 31, 0371 Oslo, Norway
| | - Cinzia Progida
- Department of Biosciences, Centre for Immune Regulation, University of Oslo, Blindernveien 31, 0371 Oslo, Norway.
| | - Oddmund Bakke
- Department of Biosciences, Centre for Immune Regulation, University of Oslo, Blindernveien 31, 0371 Oslo, Norway.
| | - Cecilia Bucci
- Department of Biological and Environmental Sciences and Technologies, (DiSTeBA) University of Salento, Via Provinciale Monteroni 165, 73100 Lecce, Italy.
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25
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Lam T, Kulp DV, Wang R, Lou Z, Taylor J, Rivera CE, Yan H, Zhang Q, Wang Z, Zan H, Ivanov DN, Zhong G, Casali P, Xu Z. Small Molecule Inhibition of Rab7 Impairs B Cell Class Switching and Plasma Cell Survival To Dampen the Autoantibody Response in Murine Lupus. THE JOURNAL OF IMMUNOLOGY 2016; 197:3792-3805. [PMID: 27742832 DOI: 10.4049/jimmunol.1601427] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2016] [Accepted: 09/09/2016] [Indexed: 02/06/2023]
Abstract
IgG autoantibodies mediate pathology in systemic lupus patients and lupus-prone mice. In this study, we showed that the class-switched IgG autoantibody response in MRL/Faslpr/lpr and C57/Sle1Sle2Sle2 mice was blocked by the CID 1067700 compound, which specifically targeted Ras-related in brain 7 (Rab7), an endosome-localized small GTPase that was upregulated in activated human and mouse lupus B cells, leading to prevention of disease development and extension of lifespan. These were associated with decreased IgG-expressing B cells and plasma cells, but unchanged numbers and functions of myeloid cells and T cells. The Rab7 inhibitor suppressed T cell-dependent and T cell-independent Ab responses, but it did not affect T cell-mediated clearance of Chlamydia infection, consistent with a B cell-specific role of Rab7. Indeed, B cells and plasma cells were inherently sensitive to Rab7 gene knockout or Rab7 activity inhibition in class switching and survival, respectively, whereas proliferation/survival of B cells and generation of plasma cells were not affected. Impairment of NF-κB activation upon Rab7 inhibition, together with the rescue of B cell class switching and plasma cell survival by enforced NF-κB activation, indicated that Rab7 mediates these processes by promoting NF-κB activation, likely through signal transduction on intracellular membrane structures. Thus, a single Rab7-inhibiting small molecule can target two stages of B cell differentiation to dampen the pathogenic autoantibody response in lupus.
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Affiliation(s)
- Tonika Lam
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas School of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229; and
| | - Dennis V Kulp
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas School of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229; and
| | - Rui Wang
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas School of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229; and
| | - Zheng Lou
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas School of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229; and
| | - Julia Taylor
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas School of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229; and
| | - Carlos E Rivera
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas School of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229; and
| | - Hui Yan
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas School of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229; and
| | - Qi Zhang
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas School of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229; and
| | - Zhonghua Wang
- Department of Biochemistry, University of Texas School of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
| | - Hong Zan
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas School of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229; and
| | - Dmitri N Ivanov
- Department of Biochemistry, University of Texas School of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
| | - Guangming Zhong
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas School of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229; and
| | - Paolo Casali
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas School of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229; and
| | - Zhenming Xu
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas School of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229; and
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26
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Multiple Roles of the Small GTPase Rab7. Cells 2016; 5:cells5030034. [PMID: 27548222 PMCID: PMC5040976 DOI: 10.3390/cells5030034] [Citation(s) in RCA: 267] [Impact Index Per Article: 33.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Revised: 08/11/2016] [Accepted: 08/12/2016] [Indexed: 12/16/2022] Open
Abstract
Rab7 is a small GTPase that belongs to the Rab family and controls transport to late endocytic compartments such as late endosomes and lysosomes. The mechanism of action of Rab7 in the late endocytic pathway has been extensively studied. Rab7 is fundamental for lysosomal biogenesis, positioning and functions, and for trafficking and degradation of several signaling receptors, thus also having implications on signal transduction. Several Rab7 interacting proteins have being identified leading to the discovery of a number of different important functions, beside its established role in endocytosis. Furthermore, Rab7 has specific functions in neurons. This review highlights and discusses the role and the importance of Rab7 on different cellular pathways and processes.
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Abstract
Mutations in PARK2 (parkin), which encodes Parkin protein, an E3 ubiquitin ligase, are associated with autosomal recessive early-onset Parkinson's disease (PD). While several studies implicated Parkin in the regulation of mitophagy and proteasomal degradation, the precise mechanism leading to neurodegeneration upon Parkin loss of function remains incompletely understood. In this study, we found that Parkin modulates the endocytic pathway through the regulation of endosomal structure and function. We showed that loss of Parkin function led to decreased endosomal tubulation and membrane association of vesicle protein sorting 35 (VPS35) and sorting nexin 1 (SNX1), as well as decreased mannose 6 phosphate receptor (M6PR), suggesting the impairment of retromer pathway in Parkin-deficient cells. We also found increased formation of intraluminal vesicles coupled with enhanced release of exosomes in the presence of mutant Parkin. To elucidate the molecular mechanism of these alterations in the endocytic pathway in Parkin-deficient cells, we found that Parkin regulates the levels and activity of Rab7 by promoting its ubiquitination on lysine 38 residue. Both endogenous Rab7 in Parkin-deficient cells and overexpressed K38 R-Rab7 mutant displayed decreased effector binding and membrane association. Furthermore, overexpression of K38R-Rab7 in HEK293 cells phenocopied the increased secretion of exosomes observed in Parkin-deficient cells, suggesting that Rab7 deregulation may be at least partially responsible for the endocytic phenotype observed in Parkin-deficient cells. These findings establish a role for Parkin in regulating the endo-lysosomal pathway and retromer function and raise the possibility that alterations in these pathways contribute to the development of pathology in Parkin-linked Parkinson's disease.
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28
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Larkin H, Costantino S, Seaman MNJ, Lavoie C. Calnuc Function in Endosomal Sorting of Lysosomal Receptors. Traffic 2016; 17:416-32. [DOI: 10.1111/tra.12374] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Revised: 01/06/2016] [Accepted: 01/06/2016] [Indexed: 02/04/2023]
Affiliation(s)
- Heidi Larkin
- Department of Pharmacology, Faculty of Medicine and Health Sciences; Université de Sherbrooke; Sherbrooke QC Canada
| | - Santiago Costantino
- Centre de recherche de l'Hôpital Maisonneuve-Rosemont; Université de Montréal; Montréal H1T 2M Canada
| | - Matthew N. J. Seaman
- Cambridge Institute for Medical Research, Department of Clinical Biochemistry, Wellcome Trust/MRC Building, Addenbrookes Hospital; University of Cambridge; Cambridge CB2 0XY UK
| | - Christine Lavoie
- Department of Pharmacology, Faculty of Medicine and Health Sciences; Université de Sherbrooke; Sherbrooke QC Canada
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29
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Pone EJ, Lam T, Lou Z, Wang R, Chen Y, Liu D, Edinger AL, Xu Z, Casali P. B cell Rab7 mediates induction of activation-induced cytidine deaminase expression and class-switching in T-dependent and T-independent antibody responses. THE JOURNAL OF IMMUNOLOGY 2015; 194:3065-78. [PMID: 25740947 DOI: 10.4049/jimmunol.1401896] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Class switch DNA recombination (CSR) is central to the maturation of the Ab response because it diversifies Ab effector functions. Like somatic hypermutation, CSR requires activation-induced cytidine deaminase (AID), whose expression is restricted to B cells, as induced by CD40 engagement or dual TLR-BCR engagement (primary CSR-inducing stimuli). By constructing conditional knockout Igh(+/C)γ(1-cre)Rab7(fl/fl) mice, we identified a B cell-intrinsic role for Rab7, a small GTPase involved in intracellular membrane functions, in mediating AID induction and CSR. Igh(+/C)γ(1-cre)Rab7(fl/fl) mice displayed normal B and T cell development and were deficient in Rab7 only in B cells undergoing Igh(C)γ(1-cre) Iγ1-Sγ1-Cγ1-cre transcription, as induced--like Igh germline Iγ1-Sγ1-Cγ1 and Iε-Sε-Cε transcription--by IL-4 in conjunction with a primary CSR-inducing stimulus. These mice could not mount T-independent or T-dependent class-switched IgG1 or IgE responses while maintaining normal IgM levels. Igh(+/C)γ(1-cre)Rab7(fl/fl) B cells showed, in vivo and in vitro, normal proliferation and survival, normal Blimp-1 expression and plasma cell differentiation, as well as intact activation of the noncanonical NF-κB, p38 kinase, and ERK1/2 kinase pathways. They, however, were defective in AID expression and CSR in vivo and in vitro, as induced by CD40 engagement or dual TLR1/2-, TLR4-, TLR7-, or TLR9-BCR engagement. In Igh(+/C)γ(1-cre)Rab7(fl/fl) B cells, CSR was rescued by enforced AID expression. These findings, together with our demonstration that Rab7-mediated canonical NF-κB activation, as critical to AID induction, outline a novel role of Rab7 in signaling pathways that lead to AID expression and CSR, likely by promoting assembly of signaling complexes along intracellular membranes.
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Affiliation(s)
- Egest J Pone
- Department of Microbiology and Immunology, School of Medicine, University of Texas Health Science Center, San Antonio, TX 78229
| | - Tonika Lam
- Department of Microbiology and Immunology, School of Medicine, University of Texas Health Science Center, San Antonio, TX 78229; Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA 92697
| | - Zheng Lou
- Department of Microbiology and Immunology, School of Medicine, University of Texas Health Science Center, San Antonio, TX 78229
| | - Rui Wang
- Department of Microbiology and Immunology, School of Medicine, University of Texas Health Science Center, San Antonio, TX 78229; Xiangya Medical School, Central South University of China, 410000 Changsha, Hunan Province, China
| | - Yuhui Chen
- Center for Human Immunobiology, Texas Children's Hospital, Baylor College of Medicine, Houston, TX 77030; and
| | - Dongfang Liu
- Center for Human Immunobiology, Texas Children's Hospital, Baylor College of Medicine, Houston, TX 77030; and
| | - Aimee L Edinger
- Department of Developmental and Cell Biology, University of California, Irvine, Irvine, CA 92697
| | - Zhenming Xu
- Department of Microbiology and Immunology, School of Medicine, University of Texas Health Science Center, San Antonio, TX 78229;
| | - Paolo Casali
- Department of Microbiology and Immunology, School of Medicine, University of Texas Health Science Center, San Antonio, TX 78229;
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30
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Agola JO, Sivalingam D, Cimino DF, Simons PC, Buranda T, Sklar LA, Wandinger-Ness A. Quantitative bead-based flow cytometry for assaying Rab7 GTPase interaction with the Rab-interacting lysosomal protein (RILP) effector protein. Methods Mol Biol 2015; 1298:331-54. [PMID: 25800855 PMCID: PMC6033261 DOI: 10.1007/978-1-4939-2569-8_28] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/24/2023]
Abstract
Rab7 facilitates vesicular transport and delivery from early endosomes to late endosomes as well as from late endosomes to lysosomes. The role of Rab7 in vesicular transport is dependent on its interactions with effector proteins, among them Rab-interacting lysosomal protein (RILP), which aids in the recruitment of active Rab7 (GTP-bound) onto dynein-dynactin motor complexes to facilitate late endosomal transport on the cytoskeleton. Here we detail a novel bead-based flow cytometry assay to measure Rab7 interaction with the Rab-interacting lysosomal protein (RILP) effector protein and demonstrate its utility for quantitative assessment and studying drug-target interactions. The specific binding of GTP-bound Rab7 to RILP is readily demonstrated and shown to be dose-dependent and saturable enabling K d and B max determinations. Furthermore, binding is nearly instantaneous and temperature-dependent. In a novel application of the assay method, a competitive small molecule inhibitor of Rab7 nucleotide binding (CID 1067700 or ML282) is shown to inhibit the Rab7-RILP interaction. Thus, the assay is able to distinguish that the small molecule, rather than incurring the active conformation, instead 'locks' the GTPase in the inactive conformation. Together, this work demonstrates the utility of using a flow cytometry assay to quantitatively characterize protein-protein interactions involving small GTPases and which has been adapted to high-throughput screening. Further, the method provides a platform for testing small molecule effects on protein-protein interactions, which can be relevant to drug discovery and development.
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Affiliation(s)
- Jacob O Agola
- Department of Pathology, University of New Mexico School of Medicine, Albuquerque, NM, 87131, USA
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31
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Steffan JJ, Dykes SS, Coleman DT, Adams LK, Rogers D, Carroll JL, Williams BJ, Cardelli JA. Supporting a role for the GTPase Rab7 in prostate cancer progression. PLoS One 2014; 9:e87882. [PMID: 24505328 PMCID: PMC3914878 DOI: 10.1371/journal.pone.0087882] [Citation(s) in RCA: 50] [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: 08/18/2013] [Accepted: 01/05/2014] [Indexed: 02/06/2023] Open
Abstract
Invasion and subsequent metastasis is the major cause of death from most cancers including prostate cancer. Herein we report on the potential tumor suppressive properties of Rab7, a GTPase that regulates trafficking of lysosomes. The movement of lysosomes to the cell surface in response to environmental cues increases the secretion of proteinases and cell invasion. We determined that Troglitazone and other members of the Thiazolidinedione family inhibit cell-surface directed lysosome trafficking and cathepsin B secretion through a Rab7-dependent mechanism. Moreover, Rab7 shRNA expressing cells were found to be more invasive in vitro and in vivo. Increased invasiveness was accompanied by elevated expression of the c-Met receptor and prolonged downstream signaling, thereby supporting a role for Rab7 as a mediator of signaling down-regulation. Taken together, these results suggested that Rab7 acts as a negative regulator of prostate tumor growth and invasion, providing further evidence for its potential as a tumor suppressor.
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Affiliation(s)
- Joshua J. Steffan
- Department of Microbiology and Immunology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
- Feist-Weiller Cancer Center, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
- Department of Natural Science, Dickinson State University, Dickinson, North Dakota, United States of America
| | - Samantha S. Dykes
- Department of Microbiology and Immunology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
- Feist-Weiller Cancer Center, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
| | - David T. Coleman
- Department of Microbiology and Immunology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
- Feist-Weiller Cancer Center, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
| | - Lisa K. Adams
- Feist-Weiller Cancer Center, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
| | - Donna Rogers
- Feist-Weiller Cancer Center, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
| | - Jennifer L. Carroll
- Feist-Weiller Cancer Center, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
| | - B. Jill Williams
- Feist-Weiller Cancer Center, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
- Department of Urology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
| | - James A. Cardelli
- Department of Microbiology and Immunology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
- Feist-Weiller Cancer Center, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
- * E-mail:
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Chukkapalli S, Amessou M, Dekhil H, Dilly AK, Liu Q, Bandyopadhyay S, Thomas RD, Bejna A, Batist G, Kandouz M. Ehd3, a regulator of vesicular trafficking, is silenced in gliomas and functions as a tumor suppressor by controlling cell cycle arrest and apoptosis. Carcinogenesis 2013; 35:877-85. [PMID: 24306026 DOI: 10.1093/carcin/bgt399] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
EHD3 [Eps15 homology (EH) domain-containing protein 3] is a protein that resides in tubular and vesicular membrane structures and participates in endocytic recycling, although all its functions are unknown. Since Ehd3 is most abundantly expressed in brain tissues, we examined its role in brain cancer progression. Using immunohistochemistry, we report loss of EHD3 expression in gliomas, including low-grade astrocytomas, suggesting that this is an early event in gliomagenesis. EHD3 expression is also very low in most of glioma cell lines tested. In two cell lines, a bisulfite sequencing method identifies promoter hypermethylation as a mechanism of Ehd3 silencing, and its expression was restored by the demethylating agent 5-Azacytidine. Doxycycline-inducible restoration of EHD3 expression to glioma cells decreases their growth and invasiveness and induces cell cycle arrest and apoptosis. Furthermore, shRNA-mediated Ehd3 silencing increases cell growth. Using a xenograft model, we demonstrate Ehd3 growth inhibitory functions in glioma cells in vivo. We suggest that Ehd3 functions as a tumor suppressor gene and loss of its expression is a very common event in gliomas. This is the first study to highlight the importance of a member of the C-terminal EHD proteins in cancer and to link their functions to the cell cycle and apoptosis.
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Affiliation(s)
- Sahiti Chukkapalli
- Department of Pathology, Wayne State University School of Medicine, Detroit, MI 48201, USA
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33
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Abstract
Retrograde trophic signaling of nerve growth factor (NGF) supports neuronal survival and differentiation. Dysregulated trophic signaling could lead to various neurological disorders. Charcot-Marie-Tooth type 2B (CMT2B) is one of the most common inherited peripheral neuropathies characterized by severe terminal axonal loss. Genetic analysis of human CMT2B patients has revealed four missense point mutations in Rab7, a small GTPase that regulates late endosomal/lysosomal pathways, but the exact pathological mechanism remains poorly understood. Here, we show that these Rab7 mutants dysregulated axonal transport and diminished the retrograde signaling of NGF and its TrkA receptor. We found that all CMT2B Rab7 mutants were transported significantly faster than Rab7(wt) in the anterograde direction, accompanied with an increased percentile of anterograde Rab7-vesicles within axons of rat E15.5 dorsal root ganglion (DRG) neurons. In PC12M cells, the CMT2B Rab7 mutants drastically reduced the level of surface TrkA and NGF binding, presumably by premature degradation of TrkA. On the other hand, siRNA knock-down of endogenous Rab7 led to the appearance of large TrkA puncta in enlarged Rab5-early endosomes within the cytoplasm, suggesting delayed TrkA degradation. We also show that CMT2B Rab7 mutants markedly impaired NGF-induced Erk1/2 activation and differentiation in PC12M cells. Further analysis revealed that CMT2B Rab7 mutants caused axonal degeneration in rat E15.5 DRG neurons. We propose that Rab7 mutants induce premature degradation of retrograde NGF-TrkA trophic signaling, which may potentially contribute to the CMT2B disease.
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34
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Mousa SA, Shaqura M, Khalefa BI, Zöllner C, Schaad L, Schneider J, Shippenberg TS, Richter JF, Hellweg R, Shakibaei M, Schäfer M. Rab7 silencing prevents μ-opioid receptor lysosomal targeting and rescues opioid responsiveness to strengthen diabetic neuropathic pain therapy. Diabetes 2013; 62:1308-19. [PMID: 23230081 PMCID: PMC3609597 DOI: 10.2337/db12-0590] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Painful diabetic neuropathy is poorly controlled by analgesics and requires high doses of opioids, triggering side effects and reducing patient quality of life. This study investigated whether enhanced Rab7-mediated lysosomal targeting of peripheral sensory neuron μ-opioid receptors (MORs) is responsible for diminished opioid responsiveness in rats with streptozotocin-induced diabetes. In diabetic animals, significantly impaired peripheral opioid analgesia was associated with a loss in sensory neuron MOR and a reduction in functional MOR G-protein-coupling. In control animals, MORs were retained mainly on the neuronal cell membrane. In contrast, in diabetic rats, they were colocalized with upregulated Rab7 in LampI-positive perinuclear lysosome compartments. Silencing endogenous Rab7 with intrathecal Rab7-siRNA or, indirectly, by reversing nerve growth factor deprivation in peripheral sensory neurons not only prevented MOR targeting to lysosomes, restoring their plasma membrane density, but also rescued opioid responsiveness toward better pain relief. These findings elucidate in vivo the mechanisms by which enhanced Rab7 lysosomal targeting of MORs leads to a loss in opioid antinociception in diabetic neuropathic pain. This is in contrast to peripheral sensory neuron MOR upregulation and antinociception in inflammatory pain, and provides intriguing evidence that regulation of opioid responsiveness varies as a function of pain pathogenesis.
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Affiliation(s)
- Shaaban A Mousa
- Department of Anaesthesiology and Intensive Care Medicine, Charité University Berlin, Campus Virchow Klinikum and Campus Charite Mitte, Berlin, Germany.
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35
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Altman BJ, Rathmell JC. Metabolic stress in autophagy and cell death pathways. Cold Spring Harb Perspect Biol 2012; 4:a008763. [PMID: 22952396 DOI: 10.1101/cshperspect.a008763] [Citation(s) in RCA: 138] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Growth factors and oncogenic kinases play important roles in stimulating cell growth during development and transformation. These processes have significant energetic and synthetic requirements and it is apparent that a central function of growth signals is to promote glucose metabolism to support these demands. Because metabolic pathways represent a fundamental aspect of cell proliferation and survival, there is considerable interest in targeting metabolism as a means to eliminate cancer. A challenge, however, is that molecular links between metabolic stress and cell death are poorly understood. Here we review current literature on how cells cope with metabolic stress and how autophagy, apoptosis, and necrosis are tightly linked to cell metabolism. Ultimately, understanding of the interplay between nutrients, autophagy, and cell death will be a key component in development of new treatment strategies to exploit the altered metabolism of cancer cells.
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Affiliation(s)
- Brian J Altman
- Department of Pharmacology and Cancer Biology, Duke University, Durham, North Carolina 27710, USA
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36
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Russell MRG, Shideler T, Nickerson DP, West M, Odorizzi G. Class E compartments form in response to ESCRT dysfunction in yeast due to hyperactivity of the Vps21 Rab GTPase. J Cell Sci 2012; 125:5208-20. [PMID: 22899724 DOI: 10.1242/jcs.111310] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The endosomal sorting complexes required for transport (ESCRTs) mediate the budding of intralumenal vesicles (ILVs) at late endosomes. ESCRT dysfunction causes drastic changes in endosome morphology, which are manifested in Saccharomyces cerevisiae by the formation of aberrant endosomes known as class E compartments. Except for the absence of ILVs, the mechanistic basis for class E compartment biogenesis is unknown. We used electron microscopy to examine endosomal morphology in response to transient ESCRT inactivation and recovery in yeast expressing the temperature-sensitive mutant vps4(ts) allele. Our results show class E compartments accumulate fourfold the amount of membrane normally present at multivesicular bodies and that multivesicular bodies can form directly from class E compartments upon recovery of ESCRT function. We found class E compartment formation requires Vps21, which is orthologous to the Rab5A GTPase in metazoans that promotes fusion of endocytic vesicles with early endosomes and homotypic fusion of early endosomes with one another. We also determined that class E compartments accumulate GTP-bound Vps21 and its effector, the class C core vacuole/endosome tethering (CORVET). Ypt7, the yeast ortholog of Rab7 that in metazoans promotes fusion of late endosomes with lysosomes, also accumulates at class E compartments but without its effector, the homotypic fusion and protein sorting (HOPS), signifying that Ypt7 at class E compartments is dysfunctional. These results suggest that failure to complete Rab5-Rab7 conversion is a consequence of ESCRT dysfunction, which results in Vps21 hyperactivity that drives the class E compartment morphology. Indeed, genetic disruption of Rab conversion without ESCRT dysfunction autonomously drives the class E compartment morphology without blocking ILV budding.
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Affiliation(s)
- Matthew R G Russell
- Department of Molecular, Cellular and Developmental Biology, University of Colorado at Boulder, Campus Box 347, Boulder, CO 80309, USA
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A hypothetical model of cargo-selective rab recruitment during organelle maturation. Cell Biochem Biophys 2012; 63:59-71. [PMID: 22328341 DOI: 10.1007/s12013-012-9341-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Rabs constitute a group of small GTPases that confer directionality to intracellular vesicle transport by promoting on the membrane of transport vesicles in the formation of specific protein complexes allowing for efficient fusion with a selected set of target organelles. The molecular mechanism controlling recruitment of the correct Rab at the right time is not fully understood. We propose a model according to which the residence time of a given Rab on the membrane of an organelle is determined by its transient trapping into a Rab effector complex (REC) composed of cargo receptor, SNAREs and further effectors. The stability of REC is controlled by the conformational state of the receptor which may change due to binding and release of cargo or changes in the luminal ion milieu. We use a conceptual mathematical model to calculate temporal changes in the Rab decoration of an organelle brought about by exchange with a cytosolic pool of Rabs or alternatively by budding and uptake of Rab-carrying vesicles. Considering the time-dependent drop in pH as one crucial factor for the conformational change of endocytic cargo receptors, our model provides a good quantitative description of the switch from Rab5 to Rab7 during the early-to-late endosome transition and correctly explains the arrest of this transition at insufficient luminal acidification. Model simulations suggest that a switch from one Rab to another may be continuous or abrupt. We discuss mechanisms, e.g. specific signalling pathways, which may restore an arrested organelle maturation.
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Endocytic pathway rapidly delivers internalized molecules to lysosomes: an analysis of vesicle trafficking, clustering and mass transfer. J Control Release 2012; 162:76-83. [PMID: 22609352 DOI: 10.1016/j.jconrel.2012.05.022] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2012] [Revised: 04/26/2012] [Accepted: 05/10/2012] [Indexed: 11/22/2022]
Abstract
Lysosomes play a critical role in intracellular drug delivery. For enzyme-based therapies, they represent a potential target site whereas for nucleic acid or many protein drugs, they represent the potential degradation site. Either way, understanding the mechanisms and processes involved in routing of materials to lysosomes after cellular entry is of high interest to the field of drug delivery. Most therapeutic cargoes other than small hydrophobic molecules enter the cells through endocytosis. Endocytosed cargoes are routed to lysosomes via microtubule-based transport and are ultimately shared by various lysosomes via tethering and clustering of endocytic vesicles followed by exchange of their contents. Using a combined experimental and numerical approach, here we studied the rates of mass transfer into and among the endocytic vesicles in a model cell line, 3T3 fibroblasts. In order to understand the relationship of mass transfer with microtubular transport and vesicle clustering, we varied both properties through various pharmacological agents. At the same time, microtubular transport and vesicle clustering were modeled through diffusion-advection equations and the Smoluchowski equations, respectively. Our analysis revealed that the rate of mass transfer is optimally related to microtubular transport and clustering properties of vesicles. Further, the rate of mass transfer is highest in the innate state of the cell. Any perturbation to either microtubular transport or vesicle aggregation led to reduced mass transfer to lysosome. These results suggest that in the absence of an external intervention the endocytic pathway appears to maximize molecular delivery to lysosomes. Strategies are discussed to reduce mass transfer to lysosomes so as to extend the residence time of molecules in endosomes or late endosomes, thus potentially increasing the likelihood of their escape before disposition in the lysosomes.
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Wang T, Zhang M, Ma Z, Guo K, Tergaonkar V, Zeng Q, Hong W. A role of Rab7 in stabilizing EGFR-Her2 and in sustaining Akt survival signal. J Cell Physiol 2012; 227:2788-97. [PMID: 21928319 DOI: 10.1002/jcp.23023] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Rab7 plays an important role in regulating endocytic traffic. In view of an emerging role of membrane traffic in signaling and diseases, we have examined the possible role of Rab7 in oncogenesis. The role of Rab7 was investigated using shRNA-mediated knockdown in A431 and MCF7 cancer cells. To our surprise, Rab7 knockdown effectively suppressed anchorage-independent growth of cancer cells in soft agar. Anoikis (matrix-detachment triggered apoptosis) was enhanced, while the level of phosphorylated (active) Akt (which is a key survival factor) was significantly reduced. Also intriguing was the observation that EGFR and Her2 levels were significantly reduced when Rab7 was knocked-down. More robust reduction of EGFR and Her2 levels was observed when knocked-down cells were treated with HSP90 inhibitor geldanamycin (GA). Low concentration of GA (50-100 nm)-induced apoptosis of the Rab7 knocked-down cells but not control cells, suggesting that Rab7 and HSP90 together contribute to the optimal stability of EGFR and Her2 as well as to protect cancer cells from apoptosis. Rab7 seems to protect EGFR and Her2 from proteosome-mediated degradation. These results suggest that Rab7 is likely involved in protecting EGFR and Her2 from being degraded by the proteosome and in maintaining optimal Akt survival signal (especially during cell detachment or when HSP90 is inhibited). Rab7 is potentially a novel target for combinatory therapy with Hsp90 inhibitors.
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Affiliation(s)
- Tuanlao Wang
- School of Pharmaceutical Sciences, Institute for Biomedical Research, Xiamen University, Fujian, China.
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40
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Naydenov NG, Harris G, Brown B, Schaefer KL, Das SK, Fisher PB, Ivanov AI. Loss of soluble N-ethylmaleimide-sensitive factor attachment protein α (αSNAP) induces epithelial cell apoptosis via down-regulation of Bcl-2 expression and disruption of the Golgi. J Biol Chem 2011; 287:5928-41. [PMID: 22194596 DOI: 10.1074/jbc.m111.278358] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Intracellular trafficking represents a key mechanism that regulates cell fate by participating in either prodeath or prosurvival signaling. Soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein α (αSNAP) is a well known component of vesicle trafficking machinery that mediates intermembrane fusion. αSNAP increases cell resistance to cytotoxic stimuli, although mechanisms of its prosurvival function are poorly understood. In this study, we found that either siRNA-mediated knockdown of αSNAP or expression of its dominant negative mutant induced epithelial cell apoptosis. Apoptosis was not caused by activation of the major prodeath regulators Bax and p53 and was independent of a key αSNAP binding partner, NSF. Instead, death of αSNAP-depleted cells was accompanied by down-regulation of the antiapoptotic Bcl-2 protein; it was mimicked by inhibition and attenuated by overexpression of Bcl-2. Knockdown of αSNAP resulted in impairment of Golgi to endoplasmic reticulum (ER) trafficking and fragmentation of the Golgi. Moreover, pharmacological disruption of ER-Golgi transport by brefeldin A and eeyarestatin 1 or siRNA-mediated depletion of an ER/Golgi-associated p97 ATPase recapitulated the effects of αSNAP inhibition by decreasing Bcl-2 level and triggering apoptosis. These results reveal a novel role for αSNAP in promoting epithelial cell survival by unique mechanisms involving regulation of Bcl-2 expression and Golgi biogenesis.
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Affiliation(s)
- Nayden G Naydenov
- Department of Medicine, University of Rochester, Rochester, New York 14642, USA
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41
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Daniele T, Hackmann Y, Ritter AT, Wenham M, Booth S, Bossi G, Schintler M, Auer-Grumbach M, Griffiths GM. A role for Rab7 in the movement of secretory granules in cytotoxic T lymphocytes. Traffic 2011; 12:902-11. [PMID: 21438969 PMCID: PMC4116565 DOI: 10.1111/j.1600-0854.2011.01194.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Cytotoxic T lymphocytes (CTL) are potent killers of virally infected and tumorigenic cells. Upon recognition of target cells, CTL undergo polarized secretion of secretory lysosomes at the immunological synapse (IS) that forms between CTL and target. However, the molecular machinery involved in the polarization of secretory lysosomes is still largely uncharacterized. In this paper, we investigated the role of Rab7 in the polarization of secretory lysosomes. We show that silencing of Rab7 by RNA interference reduces the ability of CTL to kill targets. GTP-bound Rab7 and Rab interacting lysosomal protein, RILP, interact and both localize to secretory lysosomes in CTL. Over-expression of RILP recruits dynein to the membranes of secretory lysosomes and triggers their movement toward the centrosome. Together, these results suggest that Rab7 may play a role in secretory lysosome movement toward the centrosome by interacting with RILP to recruit the minus-end motor, dynein.
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Affiliation(s)
- Tiziana Daniele
- Cambridge Institute for Medical Research, Hills Road, Cambridge CB2 0XY, UK
- San Raffaele Scientific Institute (DIBIT), via Olgettina 58, 20132 Milano, Italy
| | - Yvonne Hackmann
- Cambridge Institute for Medical Research, Hills Road, Cambridge CB2 0XY, UK
| | - Alex T. Ritter
- Cambridge Institute for Medical Research, Hills Road, Cambridge CB2 0XY, UK
| | - Matt Wenham
- Cambridge Institute for Medical Research, Hills Road, Cambridge CB2 0XY, UK
| | - Sarah Booth
- The Weatherall Institute of Molecular Medicine, Headington, Oxford OX3 9DS, UK
| | | | - Michael Schintler
- Institute of Human Genetics, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria
- University Clinic of Internal Medicine, Division of Endocrinology and Nuclear Medicine, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria
| | - Michaela Auer-Grumbach
- Institute of Human Genetics, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria
- University Clinic of Internal Medicine, Division of Endocrinology and Nuclear Medicine, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria
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42
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Zafar S, von Ahsen N, Oellerich M, Zerr I, Schulz-Schaeffer WJ, Armstrong VW, Asif AR. Proteomics Approach to Identify the Interacting Partners of Cellular Prion Protein and Characterization of Rab7a Interaction in Neuronal Cells. J Proteome Res 2011; 10:3123-35. [DOI: 10.1021/pr2001989] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Saima Zafar
- Department of Clinical Chemistry, ‡Department of Neurobiology, and §Department of Neuropathology, University Medical Center Goettingen (UMG), Robert-Koch-Strasse 40, 37075, Goettingen, Germany
| | - Nicolas von Ahsen
- Department of Clinical Chemistry, ‡Department of Neurobiology, and §Department of Neuropathology, University Medical Center Goettingen (UMG), Robert-Koch-Strasse 40, 37075, Goettingen, Germany
| | - Michael Oellerich
- Department of Clinical Chemistry, ‡Department of Neurobiology, and §Department of Neuropathology, University Medical Center Goettingen (UMG), Robert-Koch-Strasse 40, 37075, Goettingen, Germany
| | - Inga Zerr
- Department of Clinical Chemistry, ‡Department of Neurobiology, and §Department of Neuropathology, University Medical Center Goettingen (UMG), Robert-Koch-Strasse 40, 37075, Goettingen, Germany
| | - Walter J. Schulz-Schaeffer
- Department of Clinical Chemistry, ‡Department of Neurobiology, and §Department of Neuropathology, University Medical Center Goettingen (UMG), Robert-Koch-Strasse 40, 37075, Goettingen, Germany
| | - Victor W. Armstrong
- Department of Clinical Chemistry, ‡Department of Neurobiology, and §Department of Neuropathology, University Medical Center Goettingen (UMG), Robert-Koch-Strasse 40, 37075, Goettingen, Germany
| | - Abdul R. Asif
- Department of Clinical Chemistry, ‡Department of Neurobiology, and §Department of Neuropathology, University Medical Center Goettingen (UMG), Robert-Koch-Strasse 40, 37075, Goettingen, Germany
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Overmeyer JH, Young AM, Bhanot H, Maltese WA. A chalcone-related small molecule that induces methuosis, a novel form of non-apoptotic cell death, in glioblastoma cells. Mol Cancer 2011; 10:69. [PMID: 21639944 PMCID: PMC3118192 DOI: 10.1186/1476-4598-10-69] [Citation(s) in RCA: 122] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2011] [Accepted: 06/06/2011] [Indexed: 01/19/2023] Open
Abstract
Background Methuosis is a unique form of non-apoptotic cell death triggered by alterations in the trafficking of clathrin-independent endosomes, ultimately leading to extreme vacuolization and rupture of the cell. Results Here we describe a novel chalcone-like molecule, 3-(2-methyl-1H- indol-3-yl)-1-(4-pyridinyl)-2-propen-1-one (MIPP) that induces cell death with the hallmarks of methuosis. MIPP causes rapid accumulation of vacuoles derived from macropinosomes, based on time-lapse microscopy and labeling with extracellular fluid phase tracers. Vacuolization can be blocked by the cholesterol-interacting compound, filipin, consistent with the origin of the vacuoles from non-clathrin endocytic compartments. Although the vacuoles rapidly acquire some characteristics of late endosomes (Rab7, LAMP1), they remain distinct from lysosomal and autophagosomal compartments, suggestive of a block at the late endosome/lysosome boundary. MIPP appears to target steps in the endosomal trafficking pathway involving Rab5 and Rab7, as evidenced by changes in the activation states of these GTPases. These effects are specific, as other GTPases (Rac1, Arf6) are unaffected by the compound. Cells treated with MIPP lose viability within 2-3 days, but their nuclei show no evidence of apoptotic changes. Inhibition of caspase activity does not protect the cells, consistent with a non-apoptotic death mechanism. U251 glioblastoma cells selected for temozolomide resistance showed sensitivity to MIPP-induced methuosis that was comparable to the parental cell line. Conclusions MIPP might serve as a prototype for new drugs that could be used to induce non-apoptotic death in cancers that have become refractory to agents that work through DNA damage and apoptotic mechanisms.
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Affiliation(s)
- Jean H Overmeyer
- Department of Biochemistry and Cancer Biology, University of Toledo College of Medicine, Toledo, Ohio, USA
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44
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Bains M, Zaegel V, Mize-Berge J, Heidenreich KA. IGF-I stimulates Rab7-RILP interaction during neuronal autophagy. Neurosci Lett 2011; 488:112-7. [PMID: 20849920 PMCID: PMC3027408 DOI: 10.1016/j.neulet.2010.09.018] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2010] [Revised: 08/12/2010] [Accepted: 09/03/2010] [Indexed: 11/19/2022]
Abstract
Restoration of autophagy represents a potential therapeutic target for neurodegenerative disorders, but factors that regulate autophagic flux are largely unknown. When deprived of trophic factors, cultured Purkinje neurons die by an autophagy associated cell death mechanism. The accumulation of autophagic vesicles and cell death of Purkinje neurons is inhibited by insulin-like growth factor, by a mechanism that enhances autophagic vesicle turnover. In this report, we identify Rab7 as an IGF-I regulated target during neuronal autophagy. Purkinje neurons transfected with EGFP-Rab7-WT and constitutively active EGFP-Rab7-Q67L contained few RFP-LC3 positive autophagosomes and little co-localization with GFP-Rab7 under control conditions. Upon induction of autophagy, RFP-LC3 positive autophagosomes increased and co-localized with GFP-Rab7. Conversely, expression of the dominant negative mutant EGFP-Rab7-T22N increased the accumulation of autophagosomes under control conditions, which accumulated even further during trophic factor withdrawal. There was no vesicular co-localization between Rab7-T22N and RFP-LC3 under control or trophic factor withdrawal conditions. During prolonged trophic factor withdrawal, a condition that leads to the accumulation of autophagic vesicles and cell death, Rab7 activity decreased significantly. IGF-I, added at the time of trophic factor withdrawal, prevented the deactivation of Rab7 and increased the interaction of Rab7 with its interacting protein (RILP), restoring autophagic flux. These results provide a novel mechanism by which IGF-I regulates autophagic flux during neuronal stress.
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Affiliation(s)
- Mona Bains
- Department of Pharmacology, University of Colorado Denver, Aurora, CO, USA
| | - Vincent Zaegel
- Department of Pharmacology, University of Colorado Denver, Aurora, CO, USA
| | - Janna Mize-Berge
- Department of Pharmacology, University of Colorado Denver, Aurora, CO, USA
| | - Kim A. Heidenreich
- Department of Pharmacology, University of Colorado Denver, Aurora, CO, USA
- Denver Veterans Affairs Medical Center, Denver, Colorado, USA
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45
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Mason EF, Zhao Y, Goraksha-Hicks P, Coloff JL, Gannon H, Jones SN, Rathmell JC. Aerobic glycolysis suppresses p53 activity to provide selective protection from apoptosis upon loss of growth signals or inhibition of BCR-Abl. Cancer Res 2010; 70:8066-76. [PMID: 20876800 DOI: 10.1158/0008-5472.can-10-0608] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Unlike the growth factor dependence of normal cells, cancer cells can maintain growth factor-independent glycolysis and survival through expression of oncogenic kinases, such as BCR-Abl. Although targeted kinase inhibition can promote cancer cell death, therapeutic resistance develops frequently, and further mechanistic understanding is needed. Cell metabolism may be central to this cell death pathway, as we have shown that growth factor deprivation leads to decreased glycolysis that promotes apoptosis via p53 activation and induction of the proapoptotic protein Puma. Here, we extend these findings to show that elevated glucose metabolism, characteristic of cancer cells, can suppress protein kinase Cδ (PKCδ)-dependent p53 activation to maintain cell survival after growth factor withdrawal. In contrast, DNA damage-induced p53 activation was PKCδ independent and was not metabolically sensitive. Both stresses required p53 Ser(18) phosphorylation for maximal activity but led to unique patterns of p53 target gene expression, showing distinct activation and response pathways for p53 that were differentially regulated by metabolism. Consistent with oncogenic kinases acting to replace growth factors, treatment of BCR-Abl-expressing cells with the kinase inhibitor imatinib led to reduced metabolism and p53- and Puma-dependent cell death. Accordingly, maintenance of glucose uptake inhibited p53 activation and promoted imatinib resistance. Furthermore, inhibition of glycolysis enhanced imatinib sensitivity in BCR-Abl-expressing cells with wild-type p53 but had little effect on p53-null cells. These data show that distinct pathways regulate p53 after DNA damage and metabolic stress and that inhibiting glucose metabolism may enhance the efficacy of and overcome resistance to targeted molecular cancer therapies.
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Affiliation(s)
- Emily F Mason
- Departments of Pharmacology and Cancer Biology and Immunology and Sarah W. Stedman Center for Nutrition and Metabolism, Duke University Medical Center, Durham, NC 27710, USA
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46
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Kawauchi T, Sekine K, Shikanai M, Chihama K, Tomita K, Kubo KI, Nakajima K, Nabeshima YI, Hoshino M. Rab GTPases-dependent endocytic pathways regulate neuronal migration and maturation through N-cadherin trafficking. Neuron 2010; 67:588-602. [PMID: 20797536 DOI: 10.1016/j.neuron.2010.07.007] [Citation(s) in RCA: 262] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/23/2010] [Indexed: 11/15/2022]
Abstract
Although membrane trafficking pathways are involved in basic cellular functions, the evolutionally expanded number of their related family proteins suggests additional roles for membrane trafficking in higher organisms. Here, we show that several Rab-dependent trafficking pathways differentially participate in neuronal migration, an essential step for the formation of the mammalian-specific six-layered brain structure. In vivo electroporation-mediated suppression of Rab5 or dynamin to block endocytosis caused a severe neuronal migration defect in mouse cerebral cortex. Among many downstream endocytic pathways, suppression of Rab11-dependent recycling pathways exhibited a similar migration disorder, whereas inhibition of Rab7-dependent lysosomal degradation pathways affected only the final phase of neuronal migration and dendrite morphology. Inhibition of Rab5 or Rab11 perturbed the trafficking of N-cadherin, whose suppression also disturbed neuronal migration. Taken together, our findings reveal physiological roles of endocytic pathways, each of which has specific functions in distinct steps of neuronal migration and maturation during mammalian brain formation.
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Affiliation(s)
- Takeshi Kawauchi
- Department of Anatomy, Keio University School of Medicine, Tokyo 160-8582, Japan.
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Peralta ER, Martin BC, Edinger AL. Differential effects of TBC1D15 and mammalian Vps39 on Rab7 activation state, lysosomal morphology, and growth factor dependence. J Biol Chem 2010; 285:16814-21. [PMID: 20363736 DOI: 10.1074/jbc.m110.111633] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The small GTPase Rab7 promotes fusion events between late endosomes and lysosomes. Rab7 activity is regulated by extrinsic signals, most likely via effects on its guanine nucleotide exchange factor (GEF) or GTPase-activating protein (GAP). Based on their homology to the yeast proteins that regulate the Ypt7 GTP binding state, TBC1D15, and mammalian Vps39 (mVps39) have been suggested to function as the Rab7 GAP and GEF, respectively. We developed an effector pull-down assay to test this model. TBC1D15 functioned as a Rab7 GAP in cells, reducing Rab7 binding to its effector protein RILP, fragmenting the lysosome, and conferring resistance to growth factor withdrawal-induced cell death. In a cellular context, TBC1D15 GAP activity was selective for Rab7. TBC1D15 overexpression did not inhibit transferrin internalization or recycling, Rab7-independent processes that require Rab4, Rab5, and Rab11 activation. TBC1D15 was thus renamed Rab7-GAP. Contrary to expectations for a Rab7 GEF, mVps39 induced lysosomal clustering without increasing Rab7 GTP binding. Moreover, a dominant-negative mVps39 mutant fragmented the lysosome and promoted growth factor independence without decreasing Rab7-GTP levels. These findings suggest that a protein other than mVps39 serves as the Rab7 GEF. In summary, although only TBC1D15/Rab7-GAP altered Rab7-GTP levels, both Rab7-GAP and mVps39 regulate lysosomal morphology and play a role in maintaining growth factor dependence.
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Affiliation(s)
- Eigen R Peralta
- Department of Developmental and Cell Biology, University of California, Irvine, California 92697-2300, USA
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48
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Establishment of extracellular signal-regulated kinase 1/2 bistability and sustained activation through Sprouty 2 and its relevance for epithelial function. Mol Cell Biol 2010; 30:1783-99. [PMID: 20123980 DOI: 10.1128/mcb.01003-09] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Our objective was to establish an experimental model of a self-sustained and bistable extracellular signal-regulated kinase 1/2 (ERK1/2) signaling process. A single stimulation of cells with cytokines causes rapid ERK1/2 activation, which returns to baseline in 4 h. Repeated stimulation leads to sustained activation of ERK1/2 but not Jun N-terminal protein kinase (JNK), p38, or STAT6. The ERK1/2 activation lasts for 3 to 7 days and depends upon a positive-feedback mechanism involving Sprouty 2. Overexpression of Sprouty 2 induces, and its genetic deletion abrogates, ERK1/2 bistability. Sprouty 2 directly activates Fyn kinase, which then induces ERK1/2 activation. A genome-wide microarray analysis shows that the bistable phospho-ERK1/2 (pERK1/2) does not induce a high level of gene transcription. This is due to its nuclear exclusion and compartmentalization to Rab5+ endosomes. Cells with sustained endosomal pERK1/2 manifest resistance against growth factor withdrawal-induced cell death. They are primed for heightened cytokine production. Epithelial cells from cases of human asthma and from a mouse model of chronic asthma manifest increased pERK1/2, which is associated with Rab5+ endosomes. The increase in pERK1/2 was associated with a simultaneous increase in Sprouty 2 expression in these tissues. Thus, we have developed a cellular model of sustained ERK1/2 activation, which may provide a mechanistic understanding of self-sustained biological processes in chronic illnesses such as asthma.
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McCray BA, Skordalakes E, Taylor JP. Disease mutations in Rab7 result in unregulated nucleotide exchange and inappropriate activation. Hum Mol Genet 2009; 19:1033-47. [PMID: 20028791 PMCID: PMC2830827 DOI: 10.1093/hmg/ddp567] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Rab GTPases are molecular switches that orchestrate vesicular trafficking, maturation and fusion by cycling between an active, GTP-bound form, and an inactive, GDP-bound form. The activity cycle is coupled to GTP hydrolysis and is tightly controlled by regulatory proteins. Missense mutations of the GTPase Rab7 cause a dominantly inherited axonal degeneration known as Charcot-Marie-Tooth type 2B through an unknown mechanism. We present the 2.8 Å crystal structure of GTP-bound L129F mutant Rab7 which reveals normal conformations of the effector binding regions and catalytic site, but an alteration to the nucleotide binding pocket that is predicted to alter GTP binding. Through extensive biochemical analysis, we demonstrate that disease-associated mutations in Rab7 do not lead to an intrinsic GTPase defect, but permit unregulated nucleotide exchange leading to both excessive activation and hydrolysis-independent inactivation. Consistent with augmented activity, mutant Rab7 shows significantly enhanced interaction with a subset of effector proteins. In addition, dynamic imaging demonstrates that mutant Rab7 is abnormally retained on target membranes. However, we show that the increased activation of mutant Rab7 is counterbalanced by unregulated, GTP hydrolysis-independent membrane cycling. Notably, disease mutations are able to rescue the membrane cycling of a GTPase-deficient mutant. Thus, we demonstrate that disease mutations uncouple Rab7 from the spatial and temporal control normally imposed by regulatory proteins and cause disease not by a gain of novel toxic function, but by misregulation of native Rab7 activity.
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Affiliation(s)
- Brett A McCray
- Department of Developmental Neurobiology, St Jude Children's Research Hospital, Memphis, TN 38105-3678, USA
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50
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Rab GTPases as coordinators of vesicle traffic. Nat Rev Mol Cell Biol 2009. [DOI: 10.1038/nrm2728 and 5410=5410-- pmza] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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