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Yoshida T, Takenaka KI, Sakamoto H, Kojima Y, Sakano T, Shibayama K, Nakamura K, Hanawa-Suetsugu K, Mori Y, Hirabayashi Y, Hirose K, Takamori S. Compartmentalization of soluble endocytic proteins in synaptic vesicle clusters by phase separation. iScience 2023; 26:106826. [PMID: 37250768 PMCID: PMC10209458 DOI: 10.1016/j.isci.2023.106826] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 04/10/2023] [Accepted: 05/02/2023] [Indexed: 05/31/2023] Open
Abstract
Synaptic vesicle (SV) clusters, which reportedly result from synapsin's capacity to undergo liquid-liquid phase separation (LLPS), constitute the structural basis for neurotransmission. Although these clusters contain various endocytic accessory proteins, how endocytic proteins accumulate in SV clusters remains unknown. Here, we report that endophilin A1 (EndoA1), the endocytic scaffold protein, undergoes LLPS under physiologically relevant concentrations at presynaptic terminals. On heterologous expression, EndoA1 facilitates the formation of synapsin condensates and accumulates in SV-like vesicle clusters via synapsin. Moreover, EndoA1 condensates recruit endocytic proteins such as dynamin 1, amphiphysin, and intersectin 1, none of which are recruited in vesicle clusters by synapsin. In cultured neurons, like synapsin, EndoA1 is compartmentalized in SV clusters through LLPS, exhibiting activity-dependent dispersion/reassembly cycles. Thus, beyond its essential function in SV endocytosis, EndoA1 serves an additional structural function by undergoing LLPS, thereby accumulating various endocytic proteins in dynamic SV clusters in concert with synapsin.
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Affiliation(s)
- Tomofumi Yoshida
- Laboratory of Neural Membrane Biology, Graduate School of Brain Science, Doshisha University, Kyoto 610-0394, Japan
| | - Koh-ichiro Takenaka
- Laboratory of Neural Membrane Biology, Graduate School of Brain Science, Doshisha University, Kyoto 610-0394, Japan
| | - Hirokazu Sakamoto
- Department of Pharmacology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Yusuke Kojima
- Department of Pharmacology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Takumi Sakano
- Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, Tokyo 113-0033, Japan
| | - Koyo Shibayama
- Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, Tokyo 113-0033, Japan
| | - Koki Nakamura
- Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, Tokyo 113-0033, Japan
| | - Kyoko Hanawa-Suetsugu
- Laboratory of Neural Membrane Biology, Graduate School of Brain Science, Doshisha University, Kyoto 610-0394, Japan
| | - Yasunori Mori
- Laboratory of Neural Membrane Biology, Graduate School of Brain Science, Doshisha University, Kyoto 610-0394, Japan
| | - Yusuke Hirabayashi
- Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, Tokyo 113-0033, Japan
| | - Kenzo Hirose
- Department of Pharmacology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
- International Research Center for Neurointelligence (WPI-IRCN), The University of Tokyo, Tokyo 113-0033, Japan
| | - Shigeo Takamori
- Laboratory of Neural Membrane Biology, Graduate School of Brain Science, Doshisha University, Kyoto 610-0394, Japan
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Hou P, Guo Y, Jin H, Sun J, Bai Y, Li W, Li L, Cao Z, Wu F, Zhang H, Li Y, Yang S, Xia X, Huang P, Wang H. Bif-1c Attenuates Viral Proliferation by Regulating Autophagic Flux Blockade Induced by the Rabies Virus CVS-11 Strain in N2a Cells. Microbiol Spectr 2023; 11:e0307922. [PMID: 37014208 PMCID: PMC10269655 DOI: 10.1128/spectrum.03079-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2022] [Accepted: 03/09/2023] [Indexed: 04/05/2023] Open
Abstract
Bax-interacting factor-1 (Bif-1) is a multifunctional protein involved in apoptosis, autophagy, and mitochondrial morphology. However, the associations between Bif-1 and viruses are poorly understood. As discrete Bif-1 isoforms are selectively expressed and exert corresponding effects, we evaluated the effects of neuron-specific/ubiquitous Bif-1 isoforms on rabies virus (RABV) proliferation. First, infection with the RABV CVS-11 strain significantly altered Bif-1 expression in mouse neuroblastoma (N2a) cells, and Bif-1 knockdown in turn promoted RABV replication. Overexpression of neuron-specific Bif-1 isoforms (Bif-1b/c/e) suppressed RABV replication. Moreover, our study showed that Bif-1c colocalized with LC3 and partially alleviated the incomplete autophagic flux induced by RABV. Taken together, our data reveal that neuron-specific Bif-1 isoforms impair the RABV replication process by abolishing autophagosome accumulation and blocking autophagic flux induced by the RABV CVS-11 strain in N2a cells. IMPORTANCE Autophagy can be triggered by viral infection and replication. Autophagosomes are generated and affect RABV replication, which differs by viral strain and infected cell type. Bax-interacting factor-1 (Bif-1) mainly has a proapoptotic function but is also involved in autophagosome formation. However, the association between Bif-1-involved autophagy and RABV infection remains unclear. In this study, our data reveal that a neuron-specific Bif-1 isoform, Bif-1c, impaired viral replication by unchoking autophagosome accumulation induced by RABV in N2a cells to a certain extent. Our study reveals for the first time that Bif-1 is involved in modulating autophagic flux and plays a crucial role in RABV replication, establishing Bif-1 as a potential therapeutic target for rabies.
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Affiliation(s)
- Pengfei Hou
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Jilin University, Changchun, China
- Changchun Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Changchun, China
| | - Yidi Guo
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Jilin University, Changchun, China
| | - Hongli Jin
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Jilin University, Changchun, China
- Changchun Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Changchun, China
| | - Jingxuan Sun
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Jilin University, Changchun, China
| | - Yujie Bai
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Jilin University, Changchun, China
| | - Wujian Li
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Jilin University, Changchun, China
- Changchun Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Changchun, China
| | - Ling Li
- National Research Center for Exotic Animal Diseases, China Animal Health and Epidemiology Center, Qingdao, China
| | - Zengguo Cao
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Jilin University, Changchun, China
- Changchun Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Changchun, China
| | - Fangfang Wu
- Changchun Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Changchun, China
| | - Haili Zhang
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Jilin University, Changchun, China
| | - Yuanyuan Li
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Jilin University, Changchun, China
| | - Songtao Yang
- Changchun Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Changchun, China
| | - Xianzhu Xia
- Changchun Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Changchun, China
| | - Pei Huang
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Jilin University, Changchun, China
| | - Hualei Wang
- Key Laboratory of Zoonosis Research, Ministry of Education, College of Veterinary Medicine, Jilin University, Changchun, China
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3
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Gharaibeh A, Maiti P, Culver R, Heileman S, Srinageshwar B, Story D, Spelde K, Paladugu L, Munro N, Muhn N, Kolli N, Rossignol J, Dunbar GL. Solid Lipid Curcumin Particles Protect Medium Spiny Neuronal Morphology, and Reduce Learning and Memory Deficits in the YAC128 Mouse Model of Huntington's Disease. Int J Mol Sci 2020; 21:E9542. [PMID: 33333883 PMCID: PMC7765279 DOI: 10.3390/ijms21249542] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Revised: 12/09/2020] [Accepted: 12/11/2020] [Indexed: 12/13/2022] Open
Abstract
Huntington's disease (HD) is a genetic neurodegenerative disorder characterized by motor, cognitive, and psychiatric symptoms, accompanied by massive neuronal degeneration in the striatum. In this study, we utilized solid lipid curcumin particles (SLCPs) and solid lipid particles (SLPs) to test their efficacy in reducing deficits in YAC128 HD mice. Eleven-month-old YAC128 male and female mice were treated orally with SLCPs (100 mg/kg) or equivalent volumes of SLPs or vehicle (phosphate-buffered saline) every other day for eight weeks. Learning and memory performance was assessed using an active-avoidance task on week eight. The mice were euthanized, and their brains were processed using Golgi-Cox staining to study the morphology of medium spiny neurons (MSNs) and Western blots to quantify amounts of DARPP-32, brain-derived neurotrophic factor (BDNF), TrkB, synaptophysin, and PSD-95. We found that both SLCPs and SLPs improved learning and memory in HD mice, as measured by the active avoidance task. We also found that SLCP and SLP treatments preserved MSNs arborization and spinal density and modulated synaptic proteins. Our study shows that SLCPs, as well as the lipid particles, can have therapeutic effects in old YAC128 HD mice in terms of recovering from HD brain pathology and cognitive deficits.
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Affiliation(s)
- Abeer Gharaibeh
- Field Neurosciences Institute Laboratory for Restorative Neurology, Central Michigan University, Mt. Pleasant, MI 48859, USA; (P.M.); (R.C.); (S.H.); (B.S.); (D.S.); (K.S.); (L.P.); (N.M.); (N.M.); (N.K.); (J.R.)
- Program in Neuroscience, Central Michigan University, Mt. Pleasant, MI 48859, USA
- Insight Research Center, Insight Institute of Neurosurgery & Neuroscience, Flint, MI 48507, USA
| | - Panchanan Maiti
- Field Neurosciences Institute Laboratory for Restorative Neurology, Central Michigan University, Mt. Pleasant, MI 48859, USA; (P.M.); (R.C.); (S.H.); (B.S.); (D.S.); (K.S.); (L.P.); (N.M.); (N.M.); (N.K.); (J.R.)
- Program in Neuroscience, Central Michigan University, Mt. Pleasant, MI 48859, USA
- Department of Psychology, Central Michigan University, Mt. Pleasant, MI 48859, USA
- Field Neurosciences Institute, Ascension St. Mary’s, Saginaw, MI 48604, USA
- College of Health and Human Services, Saginaw Valley State University, Saginaw, MI 48710, USA
| | - Rebecca Culver
- Field Neurosciences Institute Laboratory for Restorative Neurology, Central Michigan University, Mt. Pleasant, MI 48859, USA; (P.M.); (R.C.); (S.H.); (B.S.); (D.S.); (K.S.); (L.P.); (N.M.); (N.M.); (N.K.); (J.R.)
- Program in Neuroscience, Central Michigan University, Mt. Pleasant, MI 48859, USA
| | - Shiela Heileman
- Field Neurosciences Institute Laboratory for Restorative Neurology, Central Michigan University, Mt. Pleasant, MI 48859, USA; (P.M.); (R.C.); (S.H.); (B.S.); (D.S.); (K.S.); (L.P.); (N.M.); (N.M.); (N.K.); (J.R.)
- Program in Neuroscience, Central Michigan University, Mt. Pleasant, MI 48859, USA
| | - Bhairavi Srinageshwar
- Field Neurosciences Institute Laboratory for Restorative Neurology, Central Michigan University, Mt. Pleasant, MI 48859, USA; (P.M.); (R.C.); (S.H.); (B.S.); (D.S.); (K.S.); (L.P.); (N.M.); (N.M.); (N.K.); (J.R.)
- Program in Neuroscience, Central Michigan University, Mt. Pleasant, MI 48859, USA
| | - Darren Story
- Field Neurosciences Institute Laboratory for Restorative Neurology, Central Michigan University, Mt. Pleasant, MI 48859, USA; (P.M.); (R.C.); (S.H.); (B.S.); (D.S.); (K.S.); (L.P.); (N.M.); (N.M.); (N.K.); (J.R.)
- Department of Psychology, Central Michigan University, Mt. Pleasant, MI 48859, USA
| | - Kristin Spelde
- Field Neurosciences Institute Laboratory for Restorative Neurology, Central Michigan University, Mt. Pleasant, MI 48859, USA; (P.M.); (R.C.); (S.H.); (B.S.); (D.S.); (K.S.); (L.P.); (N.M.); (N.M.); (N.K.); (J.R.)
- Program in Neuroscience, Central Michigan University, Mt. Pleasant, MI 48859, USA
| | - Leela Paladugu
- Field Neurosciences Institute Laboratory for Restorative Neurology, Central Michigan University, Mt. Pleasant, MI 48859, USA; (P.M.); (R.C.); (S.H.); (B.S.); (D.S.); (K.S.); (L.P.); (N.M.); (N.M.); (N.K.); (J.R.)
- Program in Neuroscience, Central Michigan University, Mt. Pleasant, MI 48859, USA
| | - Nikolas Munro
- Field Neurosciences Institute Laboratory for Restorative Neurology, Central Michigan University, Mt. Pleasant, MI 48859, USA; (P.M.); (R.C.); (S.H.); (B.S.); (D.S.); (K.S.); (L.P.); (N.M.); (N.M.); (N.K.); (J.R.)
- Program in Neuroscience, Central Michigan University, Mt. Pleasant, MI 48859, USA
| | - Nathan Muhn
- Field Neurosciences Institute Laboratory for Restorative Neurology, Central Michigan University, Mt. Pleasant, MI 48859, USA; (P.M.); (R.C.); (S.H.); (B.S.); (D.S.); (K.S.); (L.P.); (N.M.); (N.M.); (N.K.); (J.R.)
- Program in Neuroscience, Central Michigan University, Mt. Pleasant, MI 48859, USA
| | - Nivya Kolli
- Field Neurosciences Institute Laboratory for Restorative Neurology, Central Michigan University, Mt. Pleasant, MI 48859, USA; (P.M.); (R.C.); (S.H.); (B.S.); (D.S.); (K.S.); (L.P.); (N.M.); (N.M.); (N.K.); (J.R.)
- Program in Neuroscience, Central Michigan University, Mt. Pleasant, MI 48859, USA
| | - Julien Rossignol
- Field Neurosciences Institute Laboratory for Restorative Neurology, Central Michigan University, Mt. Pleasant, MI 48859, USA; (P.M.); (R.C.); (S.H.); (B.S.); (D.S.); (K.S.); (L.P.); (N.M.); (N.M.); (N.K.); (J.R.)
- Program in Neuroscience, Central Michigan University, Mt. Pleasant, MI 48859, USA
- College of Medicine, Central Michigan University, Mount Pleasant, MI 48859, USA
| | - Gary L. Dunbar
- Field Neurosciences Institute Laboratory for Restorative Neurology, Central Michigan University, Mt. Pleasant, MI 48859, USA; (P.M.); (R.C.); (S.H.); (B.S.); (D.S.); (K.S.); (L.P.); (N.M.); (N.M.); (N.K.); (J.R.)
- Program in Neuroscience, Central Michigan University, Mt. Pleasant, MI 48859, USA
- Department of Psychology, Central Michigan University, Mt. Pleasant, MI 48859, USA
- Field Neurosciences Institute, Ascension St. Mary’s, Saginaw, MI 48604, USA
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4
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Gowrisankaran S, Houy S, Del Castillo JGP, Steubler V, Gelker M, Kroll J, Pinheiro PS, Schwitters D, Halbsgut N, Pechstein A, van Weering JRT, Maritzen T, Haucke V, Raimundo N, Sørensen JB, Milosevic I. Endophilin-A coordinates priming and fusion of neurosecretory vesicles via intersectin. Nat Commun 2020; 11:1266. [PMID: 32152276 PMCID: PMC7062783 DOI: 10.1038/s41467-020-14993-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Accepted: 02/12/2020] [Indexed: 12/17/2022] Open
Abstract
Endophilins-A are conserved endocytic adaptors with membrane curvature-sensing and -inducing properties. We show here that, independently of their role in endocytosis, endophilin-A1 and endophilin-A2 regulate exocytosis of neurosecretory vesicles. The number and distribution of neurosecretory vesicles were not changed in chromaffin cells lacking endophilin-A, yet fast capacitance and amperometry measurements revealed reduced exocytosis, smaller vesicle pools and altered fusion kinetics. The levels and distributions of the main exocytic and endocytic factors were unchanged, and slow compensatory endocytosis was not robustly affected. Endophilin-A’s role in exocytosis is mediated through its SH3-domain, specifically via a direct interaction with intersectin-1, a coordinator of exocytic and endocytic traffic. Endophilin-A not able to bind intersectin-1, and intersectin-1 not able to bind endophilin-A, resulted in similar exocytic defects in chromaffin cells. Altogether, we report that two endocytic proteins, endophilin-A and intersectin-1, are enriched on neurosecretory vesicles and regulate exocytosis by coordinating neurosecretory vesicle priming and fusion. Endophilins-A are conserved membrane-associated proteins required for endocytosis. Here, the authors report that endophilins-A also promote exocytosis of neurosecretory vesicles by coordinating priming and fusion through intersectin-1, independently of their roles in different types of endocytosis.
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Affiliation(s)
- Sindhuja Gowrisankaran
- European Neuroscience Institute-A Joint Initiative of the University Medical Center Göttingen and the Max Planck Society Göttingen, Göttingen, Germany
| | - Sébastien Houy
- University of Copenhagen, Department for Neuroscience, Faculty of Health and Medical Sciences, Copenhagen, Denmark
| | - Johanna G Peña Del Castillo
- European Neuroscience Institute-A Joint Initiative of the University Medical Center Göttingen and the Max Planck Society Göttingen, Göttingen, Germany
| | - Vicky Steubler
- European Neuroscience Institute-A Joint Initiative of the University Medical Center Göttingen and the Max Planck Society Göttingen, Göttingen, Germany
| | - Monika Gelker
- European Neuroscience Institute-A Joint Initiative of the University Medical Center Göttingen and the Max Planck Society Göttingen, Göttingen, Germany
| | - Jana Kroll
- European Neuroscience Institute-A Joint Initiative of the University Medical Center Göttingen and the Max Planck Society Göttingen, Göttingen, Germany
| | - Paulo S Pinheiro
- University of Copenhagen, Department for Neuroscience, Faculty of Health and Medical Sciences, Copenhagen, Denmark.,Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal
| | - Dirk Schwitters
- European Neuroscience Institute-A Joint Initiative of the University Medical Center Göttingen and the Max Planck Society Göttingen, Göttingen, Germany
| | - Nils Halbsgut
- European Neuroscience Institute-A Joint Initiative of the University Medical Center Göttingen and the Max Planck Society Göttingen, Göttingen, Germany
| | - Arndt Pechstein
- Leibniz Research Institute for Molecular Pharmacology, Molecular Physiology and Cell Biology Section, Berlin, Germany
| | - Jan R T van Weering
- Department of Clinical Genetics, Center for Neurogenomics and Cognitive Research, Amsterdam UMC, Amsterdam, The Netherlands
| | - Tanja Maritzen
- Leibniz Research Institute for Molecular Pharmacology, Molecular Physiology and Cell Biology Section, Berlin, Germany
| | - Volker Haucke
- Leibniz Research Institute for Molecular Pharmacology, Molecular Physiology and Cell Biology Section, Berlin, Germany
| | - Nuno Raimundo
- Institute for Cellular Biochemistry, University Medical Center Göttingen (UMG), Göttingen, Germany
| | - Jakob B Sørensen
- University of Copenhagen, Department for Neuroscience, Faculty of Health and Medical Sciences, Copenhagen, Denmark.
| | - Ira Milosevic
- European Neuroscience Institute-A Joint Initiative of the University Medical Center Göttingen and the Max Planck Society Göttingen, Göttingen, Germany.
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5
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Mitochondrial Dynamics in Stem Cells and Differentiation. Int J Mol Sci 2018; 19:ijms19123893. [PMID: 30563106 PMCID: PMC6321186 DOI: 10.3390/ijms19123893] [Citation(s) in RCA: 107] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 12/03/2018] [Accepted: 12/04/2018] [Indexed: 01/09/2023] Open
Abstract
Mitochondria are highly dynamic organelles that continuously change their shape. Their main function is adenosine triphosphate (ATP) production; however, they are additionally involved in a variety of cellular phenomena, such as apoptosis, cell cycle, proliferation, differentiation, reprogramming, and aging. The change in mitochondrial morphology is closely related to the functionality of mitochondria. Normal mitochondrial dynamics are critical for cellular function, embryonic development, and tissue formation. Thus, defects in proteins involved in mitochondrial dynamics that control mitochondrial fusion and fission can affect cellular differentiation, proliferation, cellular reprogramming, and aging. Here, we review the processes and proteins involved in mitochondrial dynamics and their various associated cellular phenomena.
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6
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Yu SC, Jánosi B, Liewald JF, Wabnig S, Gottschalk A. Endophilin A and B Join Forces With Clathrin to Mediate Synaptic Vesicle Recycling in Caenorhabditis elegans. Front Mol Neurosci 2018; 11:196. [PMID: 29962934 PMCID: PMC6010539 DOI: 10.3389/fnmol.2018.00196] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Accepted: 05/17/2018] [Indexed: 01/24/2023] Open
Abstract
Synaptic vesicle (SV) recycling enables ongoing transmitter release, even during prolonged activity. SV membrane and proteins are retrieved by ultrafast endocytosis and new SVs are formed from synaptic endosomes (large vesicles—LVs). Many proteins contribute to SV recycling, e.g., endophilin, synaptojanin, dynamin and clathrin, while the site of action of these proteins (at the plasma membrane (PM) vs. at the endosomal membrane) is only partially understood. Here, we investigated the roles of endophilin A (UNC-57), endophilin-related protein (ERP-1, homologous to human endophilin B1) and of clathrin, in SV recycling at the cholinergic neuromuscular junction (NMJ) of C. elegans. erp-1 mutants exhibited reduced transmission and a progressive reduction in optogenetically evoked muscle contraction, indicative of impaired SV recycling. This was confirmed by electrophysiology, where particularly endophilin A (UNC-57), but also endophilin B (ERP-1) mutants exhibited reduced transmission. By optogenetic and electrophysiological analysis, phenotypes in the unc-57; erp-1 double mutant are largely dominated by the unc-57 mutation, arguing for partially redundant functions of endophilins A and B, but also hinting at a back-up mechanism for neuronal endocytosis. By electron microscopy (EM), we observed that unc-57 and erp-1; unc-57 double mutants showed increased numbers of synaptic endosomes of large size, assigning a role for both proteins at the endosome, because endosomal disintegration into new SVs, but not formation of endosomes were hampered. Accordingly, only low amounts of SVs were present. Also erp-1 mutants show reduced SV numbers (but no increase in LVs), thus ERP-1 contributes to SV formation. We analyzed temperature-sensitive mutants of clathrin heavy chain (chc-1), as well as erp-1; chc-1 and unc-57; chc-1 double mutants. SV recycling phenotypes were obvious from optogenetic stimulation experiments. By EM, chc-1 mutants showed formation of numerous and large endosomes, arguing that clathrin, as shown for mammalian synapses, acts at the endosome in formation of new SVs. Without endophilins, clathrin formed endosomes at the PM, while endophilins A and B compensated for the loss of clathrin at the PM, under conditions of high SV turnover.
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Affiliation(s)
- Szi-Chieh Yu
- Buchmann Institute of Molecular Life Sciences (BMLS), Goethe University, Frankfurt, Germany.,Institute of Biophysical Chemistry, Department of Biochemistry, Chemistry and Pharmacy, Goethe University, Frankfurt, Germany
| | - Barbara Jánosi
- Buchmann Institute of Molecular Life Sciences (BMLS), Goethe University, Frankfurt, Germany.,Institute of Biophysical Chemistry, Department of Biochemistry, Chemistry and Pharmacy, Goethe University, Frankfurt, Germany
| | - Jana F Liewald
- Buchmann Institute of Molecular Life Sciences (BMLS), Goethe University, Frankfurt, Germany.,Institute of Biophysical Chemistry, Department of Biochemistry, Chemistry and Pharmacy, Goethe University, Frankfurt, Germany
| | - Sebastian Wabnig
- Buchmann Institute of Molecular Life Sciences (BMLS), Goethe University, Frankfurt, Germany.,Institute of Biophysical Chemistry, Department of Biochemistry, Chemistry and Pharmacy, Goethe University, Frankfurt, Germany
| | - Alexander Gottschalk
- Buchmann Institute of Molecular Life Sciences (BMLS), Goethe University, Frankfurt, Germany.,Institute of Biophysical Chemistry, Department of Biochemistry, Chemistry and Pharmacy, Goethe University, Frankfurt, Germany.,Cluster of Excellence Frankfurt, Macromolecular Complexes (CEF-MC), Goethe University, Frankfurt, Germany
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7
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Gan Y, Li Y, Long Z, Lee AR, Xie N, Lovnicki JM, Tang Y, Chen X, Huang J, Dong X. Roles of Alternative RNA Splicing of the Bif-1 Gene by SRRM4 During the Development of Treatment-induced Neuroendocrine Prostate Cancer. EBioMedicine 2018; 31:267-275. [PMID: 29759485 PMCID: PMC6013970 DOI: 10.1016/j.ebiom.2018.05.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Revised: 04/12/2018] [Accepted: 05/01/2018] [Indexed: 02/02/2023] Open
Abstract
Treatment-induced neuroendocrine prostate cancer (t-NEPC) is an aggressive subtype of prostate cancer (PCa) that becomes more prevalent when hormonal therapy, chemotherapy, or radiation therapy is applied to patients with metastatic prostate adenocarcinoma (AdPC). How AdPC cells survive these anti-cancer therapies and progress into t-NEPC remains unclear. By comparing the whole transcriptomes between AdPC and t-NEPC, we identified Bif-1, an apoptosis-associated gene, which undergoes alternative RNA splicing in t-NEPC. We found that while Bif-1a is the predominant variant of the Bif-1 gene in AdPC, two neural-specific variants, Bif-1b and Bif-1c, are highly expressed in t-NEPC patients, patient derived xenografts, and cell models. The neural-specific RNA splicing factor, SRRM4, promotes Bif-1b and Bif-1c splicing, and the expression of SRRM4 in tumors is strongly associated with Bif-1b/-1c levels. Furthermore, we showed that Bif-1a is pro-apoptotic, while Bif-1b and Bif-1c are anti-apoptotic in PCa cells under camptothecin and UV light irritation treatments. Taken together, our data indicate that SRRM4 regulates alternative RNA splicing of the Bif-1 gene that enables PCa cells resistant to apoptotic stimuli under anti-cancer therapies, and may contribute to AdPC progression into t-NEPC. Alternative RNA splicing of the apoptosis-related gene, Bif-1, is associated with the development of t-NEPC. SRRM4 regulates alternative RNA splicing of the Bif-1 gene. Bif-1a in AdPC cells is pro-apoptotic, while neural Bif-1 variants, Bif-1b/-1c, enable tumor cells resistant to apoptosis.
Treatment-induced neuroendocrine prostate cancer (t-NEPC) is an aggressive subtype of castration-resistant prostate cancer. It becomes more prevalent when more potent androgen receptor inhibitors are applied to patients. However, mechanisms by which t-NEPC develops remain unclear. Here we report alternative RNA splicing of the apoptosis-related gene, Bif-1, may contribute to t-NEPC establishment. We show that the expression of neural Bif-1 variants is upregulated in t-NEPC, and confers tumor cells resistance to apoptotic stimuli. We propose that tumor cells have to first develop mechanisms to counteract therapy-induced cell death before they can undergo neuroendocrine differentiation for t-NEPC.
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Affiliation(s)
- Yu Gan
- Vancouver Prostate Centre, Department of Urologic Sciences, University of British Columbia, Canada; Department of Urology, Xiangya Hospital, Central South University, Changsha, China; Department of Urology, Third Xiangya Hospital, Central South University, Changsha, China.
| | - Yinan Li
- Vancouver Prostate Centre, Department of Urologic Sciences, University of British Columbia, Canada.
| | - Zhi Long
- Vancouver Prostate Centre, Department of Urologic Sciences, University of British Columbia, Canada; Department of Urology, Third Xiangya Hospital, Central South University, Changsha, China.
| | - Ahn R Lee
- Vancouver Prostate Centre, Department of Urologic Sciences, University of British Columbia, Canada.
| | - Ning Xie
- Vancouver Prostate Centre, Department of Urologic Sciences, University of British Columbia, Canada.
| | - Jessica M Lovnicki
- Vancouver Prostate Centre, Department of Urologic Sciences, University of British Columbia, Canada.
| | - Yuxin Tang
- Department of Urology, Third Xiangya Hospital, Central South University, Changsha, China.
| | - Xiang Chen
- Department of Urology, Xiangya Hospital, Central South University, Changsha, China.
| | - Jiaoti Huang
- Department of Pathology, Duke University School of Medicine, Durham, NC, USA.
| | - Xuesen Dong
- Vancouver Prostate Centre, Department of Urologic Sciences, University of British Columbia, Canada.
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8
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Lee AR, Che N, Lovnicki JM, Dong X. Development of Neuroendocrine Prostate Cancers by the Ser/Arg Repetitive Matrix 4-Mediated RNA Splicing Network. Front Oncol 2018; 8:93. [PMID: 29666783 PMCID: PMC5891588 DOI: 10.3389/fonc.2018.00093] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Accepted: 03/16/2018] [Indexed: 12/19/2022] Open
Abstract
While the use of next-generation androgen receptor pathway inhibition (ARPI) therapy has significantly increased the survival of patients with metastatic prostate adenocarcinoma (AdPC), several groups have reported a treatment-resistant mechanism, whereby cancer cells can become androgen receptor (AR) indifferent and gain a neuroendocrine (NE)-like phenotype. This subtype of castration-resistant prostate cancer has been termed "treatment-induced castration-resistant neuroendocrine prostate cancer" (CRPC-NE). Recent reports indicate that the overall genomic landscapes of castration-resistant tumors with AdPC phenotypes and CRPC-NE are not significantly altered. However, CRPC-NE tumors have been found to contain a NE-specific pattern throughout their epigenome and splicing transcriptome, which are significantly modified. The molecular mechanisms by which CRPC-NE develops remain unclear, but several factors have been implicated in the progression of the disease. Recently, Ser/Arg repetitive matrix 4 (SRRM4), a neuronal-specific RNA splicing factor that is upregulated in CRPC-NE tumors, has been shown to establish a CRPC-NE-unique splicing transcriptome, to induce a NE-like morphology in AdPC cells, and, most importantly, to transform AdPC cells into CRPC-NE xenografts under ARPI. Moreover, the SRRM4-targeted splicing genes are highly enriched in various neuronal processes, suggesting their roles in facilitating a CRPC-NE program. This article will address the importance of SRRM4-mediated alternative RNA splicing in reprogramming translated proteins to facilitate NE differentiation, survival, and proliferation of cells to establish CRPC-NE tumors. In addition, we will discuss the potential roles of SRRM4 in conjunction with other known pathways and factors important for CRPC-NE development, such as the AR pathway, TP53 and RB1 genes, the FOXA family of proteins, and environmental factors. This study aims to explore the multifaceted functions of SRRM4 and SRRM4-mediated splicing in driving a CRPC-NE program as a coping mechanism for therapy resistance, as well as define future SRRM4-targeted therapeutic approaches for treating CRPC-NE or mitigating its development.
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Affiliation(s)
- Ahn R Lee
- Vancouver Prostate Centre, Department of Urologic Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Nicole Che
- Vancouver Prostate Centre, Department of Urologic Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Jessica M Lovnicki
- Vancouver Prostate Centre, Department of Urologic Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Xuesen Dong
- Vancouver Prostate Centre, Department of Urologic Sciences, University of British Columbia, Vancouver, BC, Canada
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9
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Li J, Barylko B, Eichorst JP, Mueller JD, Albanesi JP, Chen Y. Association of Endophilin B1 with Cytoplasmic Vesicles. Biophys J 2017; 111:565-576. [PMID: 27508440 DOI: 10.1016/j.bpj.2016.06.017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Revised: 06/14/2016] [Accepted: 06/16/2016] [Indexed: 01/21/2023] Open
Abstract
Endophilins are SH3- and BAR domain-containing proteins implicated in membrane remodeling and vesicle formation. Endophilins A1 and A2 promote the budding of endocytic vesicles from the plasma membrane, whereas endophilin B1 has been implicated in vesicle budding from intracellular organelles, including the trans-Golgi network and late endosomes. We previously reported that endophilins A1 and A2 exist almost exclusively as soluble dimers in the cytosol. Here, we present results of fluorescence fluctuation spectroscopy analyses indicating that, in contrast, the majority of endophilin B1 is present in multiple copies on small, highly mobile cytoplasmic vesicles. Formation of these vesicles was enhanced by overexpression of wild-type dynamin 2, but suppressed by expression of a catalytically inactive dynamin 2 mutant. Using dual-color heterospecies partition analysis, we identified the epidermal growth factor receptor on endophilin B1 vesicles. Moreover, a proportion of endophilin B1 vesicles also contained caveolin, whereas clathrin was almost undetectable on those vesicles. These results raise the possibility that endophilin B1 participates in dynamin 2-dependent formation of a population of transport vesicles distinct from those generated by A-type endophilins.
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Affiliation(s)
- Jinhui Li
- Department of Physics, University of Minnesota, Minneapolis, Minnesota
| | | | - John P Eichorst
- Department of Physics, University of Minnesota, Minneapolis, Minnesota
| | - Joachim D Mueller
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota
| | | | - Yan Chen
- Department of Physics, University of Minnesota, Minneapolis, Minnesota.
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10
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11
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Winther ÅME, Vorontsova O, Rees KA, Näreoja T, Sopova E, Jiao W, Shupliakov O. An Endocytic Scaffolding Protein together with Synapsin Regulates Synaptic Vesicle Clustering in the Drosophila Neuromuscular Junction. J Neurosci 2015; 35:14756-70. [PMID: 26538647 PMCID: PMC6605226 DOI: 10.1523/jneurosci.1675-15.2015] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Revised: 09/16/2015] [Accepted: 09/25/2015] [Indexed: 11/21/2022] Open
Abstract
Many endocytic proteins accumulate in the reserve pool of synaptic vesicles (SVs) in synapses and relocalize to the endocytic periactive zone during neurotransmitter release. Currently little is known about their functions outside the periactive zone. Here we show that in the Drosophila neuromuscular junction (NMJ), the endocytic scaffolding protein Dap160 colocalizes during the SV cycle and forms a functional complex with the SV-associated phosphoprotein synapsin, previously implicated in SV clustering. This direct interaction is strongly enhanced under phosphorylation-promoting conditions and is essential for proper localization of synapsin at NMJs. In a dap160 rescue mutant lacking the interaction between Dap160 and synapsin, perturbed reclustering of SVs during synaptic activity is observed. Our data indicate that in addition to the function in endocytosis, Dap160 is a component of a network of protein-protein interactions that serves for clustering of SVs in conjunction with synapsin. During the SV cycle, Dap160 interacts with synapsin dispersed from SVs and helps direct synapsin back to vesicles. The proteins function in synergy to achieve efficient clustering of SVs in the reserve pool. SIGNIFICANCE STATEMENT We provide the first evidence for the function of the SH3 domain interaction in synaptic vesicle (SV) organization at the synaptic active zone. Using Drosophila neuromuscular junction as a model synapse, we describe the molecular mechanism that enables the protein implicated in SV clustering, synapsin, to return to the pool of vesicles during neurotransmitter release. We also identify the endocytic scaffolding complex that includes Dap160 as a regulator of the events linking exocytosis and endocytosis in synapses.
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Affiliation(s)
- Åsa M E Winther
- Department of Neuroscience, Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Olga Vorontsova
- Department of Neuroscience, Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Kathryn A Rees
- Department of Neuroscience, Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Tuomas Näreoja
- Department of Neuroscience, Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Elena Sopova
- Department of Neuroscience, Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Wei Jiao
- Department of Neuroscience, Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Oleg Shupliakov
- Department of Neuroscience, Karolinska Institutet, 171 77 Stockholm, Sweden
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12
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Boubaker G, Hemphill A, Huber CO, Spiliotis M, Babba H, Gottstein B. Prevention and Immunotherapy of Secondary Murine Alveolar Echinococcosis Employing Recombinant EmP29 Antigen. PLoS Negl Trop Dis 2015; 9:e0003795. [PMID: 26053794 PMCID: PMC4460070 DOI: 10.1371/journal.pntd.0003795] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Accepted: 04/28/2015] [Indexed: 12/13/2022] Open
Abstract
Alveolar echinococcosis (AE) is caused by infection with the larval stage of the tapeworm Echinococcus multilocularis. An increasing understanding of immunological events that account for the metacestode survival in human and murine AE infection prompted us to undertake explorative experiments tackling the potential of novel preventive and/or immunotherapeutic measures. In this study, the immunoprotective and immunotherapeutic ability of recombinant EmP29 antigen (rEmP29) was assessed in mice that were intraperitoneally infected with E. multilocularis metacestodes. For vaccination, three intraperitoneal injections with 20μg rEmP29 emulsified in saponin adjuvants were applied over 6 weeks. 2 weeks after the last boost, mice were infected, and at 90 days post-infection, rEmP29-vaccinated mice exhibited a median parasite weight that was reduced by 75% and 59% when compared to NaCl- or saponin–treated control mice, respectively. For immunotherapeutical application, the rEmP29 (20μg) vaccine was administered to experimentally infected mice, starting at 1 month post-infection, three times with 2 weeks intervals. Mice undergoing rEmP29 immunotherapy exhibited a median parasite load that was reduced by 53% and 49% when compared to NaCl- and saponin–treated control mice, respectively. Upon analysis of spleen cells, both, vaccination and treatment with rEmP29, resulted in low ratios of Th2/Th1 (IL-4/IFN-γ) cytokine mRNA and low levels of mRNA coding for IL-10 and IL-2. These results suggest that reduction of the immunosuppressive environment takes place in vaccinated as well as immunotreated mice, and a shift towards a Th1 type of immune response may be responsible for the observed increased restriction of parasite growth. The present study provides the first evidence that active immunotherapy may present a sustainable route for the control of AE. Current medical management of AE that relies on surgery and continuous benzimidazole administration is of limited effectiveness. Therefore, alternative preventive and therapeutic tools need to be explored. Here, we demonstrate that vaccination with recombinant antigen EmP29 (rEmP29), prior or after secondary infection of BALB/c mice, resulted in a significant reduction of the median parasite weight when compared to different control groups. We then characterized the transcription level of splenic IL-4 and IFN-γ cytokines as hallmarks for AE-anti-protective humoral immune reaction (Th2) and for AE-effective (restrictive) cellular response (Th1), respectively. Results revealed that vaccinated mice in pre- or post-infection situation exhibited the lowest IL-4/IFN-γ mRNA ratios. In addition, those groups showed also significantly low levels of IL-10-encoding mRNA coding (immunosuppressive cytokine), as well as IL-2. These findings suggest that reduction of parasite load in rEmP29-vaccinated mice (in pre- or post-infection status) might be triggered by a decline of the immunosuppressive environment and a change of the host immune reaction towards a Th1-re-oriented cell-mediated immune defense. A similar non-specific effect appears also to be yielded by the immunostimulating adjuvants. This study provides the first insight into the potential benefits of antigen-specific immunotherapy as new treatment option of AE.
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Affiliation(s)
- Ghalia Boubaker
- Institute of Parasitology, University of Bern, Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
- Faculty of Pharmacy, Department of Clinical Biology B, Laboratory of Medical and Molecular Parasitology–Mycology (LR12ES08), University of Monastir, Monastir, Tunisia
| | - Andrew Hemphill
- Institute of Parasitology, University of Bern, Bern, Switzerland
| | | | - Markus Spiliotis
- Institute of Parasitology, University of Bern, Bern, Switzerland
| | - Hamouda Babba
- Faculty of Pharmacy, Department of Clinical Biology B, Laboratory of Medical and Molecular Parasitology–Mycology (LR12ES08), University of Monastir, Monastir, Tunisia
| | - Bruno Gottstein
- Institute of Parasitology, University of Bern, Bern, Switzerland
- * E-mail:
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13
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Wang DB, Kinoshita Y, Kinoshita C, Uo T, Sopher BL, Cudaback E, Keene CD, Bilousova T, Gylys K, Case A, Jayadev S, Wang HG, Garden GA, Morrison RS. Loss of endophilin-B1 exacerbates Alzheimer's disease pathology. Brain 2015; 138:2005-19. [PMID: 25981964 DOI: 10.1093/brain/awv128] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Accepted: 03/15/2015] [Indexed: 12/31/2022] Open
Abstract
Endophilin-B1, also known as Bax-interacting factor 1 (Bif-1, and encoded by SH3GLB1), is a multifunctional protein involved in apoptosis, autophagy and mitochondrial function. We recently described a unique neuroprotective role for neuron-specific alternatively spliced isoforms of endophilin-B1. To examine whether endophilin-B1-mediated neuroprotection could be a novel therapeutic target for Alzheimer's disease we used a double mutant amyloid precursor protein and presenilin 1 (APPswe/PSEN1dE9) mouse model of Alzheimer's disease and observed that expression of neuron-specific endophilin-B1 isoforms declined with disease progression. To determine if this reduction in endophilin-B1 has a functional role in Alzheimer's disease pathogenesis, we crossed endophilin-B1(-/-) mice with APPswe/PSEN1dE9 mice. Deletion of endophilin-B1 accelerated disease onset and progression in 6-month-old APPswe/PSEN1dE9/endophilin-B1(-/-) mice, which showed more plaques, astrogliosis, synaptic degeneration, cognitive impairment and mortality than APPswe/PSEN1dE9 mice. In mouse primary cortical neuron cultures, overexpression of neuron-specific endophilin-B1 isoforms protected against amyloid-β-induced apoptosis and mitochondrial dysfunction. Additionally, protein and mRNA levels of neuron-specific endophilin-B1 isoforms were also selectively decreased in the cerebral cortex and in the synaptic compartment of patients with Alzheimer's disease. Flow sorting of synaptosomes from patients with Alzheimer's disease demonstrated a negative correlation between amyloid-β and endophilin-B1 levels. The importance of endophilin-B1 in neuronal function was further underscored by the development of synaptic degeneration and cognitive and motor impairment in endophilin-B1(-/-) mice by 12 months. Our findings suggest that endophilin-B1 is a key mediator of a feed-forward mechanism of Alzheimer's disease pathogenesis where amyloid-β reduces neuron-specific endophilin-B1, which in turn enhances amyloid-β accumulation and neuronal vulnerability to stress.
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Affiliation(s)
- David B Wang
- 1 Department of Neurological Surgery, University of Washington School of Medicine, Seattle, WA 98195-6470, USA
| | - Yoshito Kinoshita
- 1 Department of Neurological Surgery, University of Washington School of Medicine, Seattle, WA 98195-6470, USA
| | - Chizuru Kinoshita
- 1 Department of Neurological Surgery, University of Washington School of Medicine, Seattle, WA 98195-6470, USA
| | - Takuma Uo
- 1 Department of Neurological Surgery, University of Washington School of Medicine, Seattle, WA 98195-6470, USA
| | - Bryce L Sopher
- 2 Department of Neurology, University of Washington School of Medicine, Seattle, WA 98195-6470, USA
| | - Eiron Cudaback
- 3 Department of Pathology, University of Washington School of Medicine, Seattle, WA 98195-6470, USA
| | - C Dirk Keene
- 3 Department of Pathology, University of Washington School of Medicine, Seattle, WA 98195-6470, USA
| | - Tina Bilousova
- 4 School of Nursing, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Karen Gylys
- 4 School of Nursing, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Amanda Case
- 2 Department of Neurology, University of Washington School of Medicine, Seattle, WA 98195-6470, USA
| | - Suman Jayadev
- 2 Department of Neurology, University of Washington School of Medicine, Seattle, WA 98195-6470, USA
| | - Hong-Gang Wang
- 5 Department of Pediatrics, The Pennsylvania State University College of Medicine, Hershey, PA 1703, USA
| | - Gwenn A Garden
- 2 Department of Neurology, University of Washington School of Medicine, Seattle, WA 98195-6470, USA 3 Department of Pathology, University of Washington School of Medicine, Seattle, WA 98195-6470, USA
| | - Richard S Morrison
- 1 Department of Neurological Surgery, University of Washington School of Medicine, Seattle, WA 98195-6470, USA
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14
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McMahon D, Dinh A, Kurz D, Shah D, Han GS, Carman GM, Brasaemle DL. Comparative gene identification 58/α/β hydrolase domain 5 lacks lysophosphatidic acid acyltransferase activity. J Lipid Res 2014; 55:1750-61. [PMID: 24879803 DOI: 10.1194/jlr.m051151] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2014] [Indexed: 01/07/2023] Open
Abstract
Mutations in the gene encoding comparative gene identification 58 (CGI-58)/α/β hydrolase domain 5 (ABHD5) cause Chanarin-Dorfman syndrome, characterized by excessive triacylglycerol storage in cells and tissues. CGI-58 has been identified as a coactivator of adipose TG lipase (ATGL) and a lysophosphatidic acid acyltransferase (LPAAT). We developed a molecular model of CGI-58 structure and then mutated predicted active site residues and performed LPAAT activity assays of recombinant WT and mutated CGI-58. When mutations of predicted catalytic residues failed to reduce LPAAT activity, we determined that LPAAT activity was due to a bacterial contaminant of affinity purification procedures, plsC, the sole LPAAT in Escherichia coli Purification protocols were optimized to reduce plsC contamination, in turn reducing LPAAT activity. When CGI-58 was expressed in SM2-1(DE3) cells that lack plsC, lysates lacked LPAAT activity. Additionally, mouse CGI-58 expressed in bacteria as a glutathione-S-transferase fusion protein and human CGI-58 expressed in yeast lacked LPAAT activity. Previously reported lipid binding activity of CGI-58 was revisited using protein-lipid overlays. Recombinant CGI-58 failed to bind lysophosphatidic acid, but interestingly, bound phosphatidylinositol 3-phosphate [PI(3)P] and phosphatidylinositol 5-phosphate [PI(5)P]. Prebinding CGI-58 with PI(3)P or PI(5)P did not alter its coactivation of ATGL in vitro. In summary, purified recombinant CGI-58 that is functional as an ATGL coactivator lacks LPAAT activity.
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Affiliation(s)
- Derek McMahon
- Rutgers Center for Lipid Research and Department of Nutritional Sciences and Rutgers Center for Lipid Research and Department of Food Science
| | - Anna Dinh
- Rutgers Center for Lipid Research and Department of Nutritional Sciences and Rutgers Center for Lipid Research and Department of Food Science
| | - Daniel Kurz
- Rutgers Center for Lipid Research and Department of Nutritional Sciences and Rutgers Center for Lipid Research and Department of Food Science
| | - Dharika Shah
- Rutgers Center for Lipid Research and Department of Nutritional Sciences and Rutgers Center for Lipid Research and Department of Food Science
| | - Gil-Soo Han
- Rutgers, The State University of New Jersey, New Brunswick, NJ 08901
| | - George M Carman
- Rutgers, The State University of New Jersey, New Brunswick, NJ 08901
| | - Dawn L Brasaemle
- Rutgers Center for Lipid Research and Department of Nutritional Sciences and Rutgers Center for Lipid Research and Department of Food Science
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15
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Abstract
Bax-interacting factor 1 (Bif-1, also known as endophilin B1) is a multifunctional protein involved in the regulation of apoptosis, mitochondrial morphology, and autophagy. Previous studies in non-neuronal cells have shown that Bif-1 is proapoptotic and promotes mitochondrial fragmentation. However, the role of Bif-1 in postmitotic neurons has not been investigated. In contrast to non-neuronal cells, we now report that in neurons Bif-1 promotes viability and mitochondrial elongation. In mouse primary cortical neurons, Bif-1 knockdown exacerbated apoptosis induced by the DNA-damaging agent camptothecin. Neurons from Bif-1-deficient mice contained fragmented mitochondria and Bif-1 knockdown in wild-type neurons also resulted in fragmented mitochondria which were more depolarized, suggesting mitochondrial dysfunction. During ischemic stroke, Bif-1 expression was downregulated in the penumbra of wild-type mice. Consistent with Bif-1 being required for neuronal viability, Bif-1-deficient mice developed larger infarcts and an exaggerated astrogliosis response following ischemic stroke. Together, these data suggest that, in contrast to non-neuronal cells, Bif-1 is essential for the maintenance of mitochondrial morphology and function in neurons, and that loss of Bif-1 renders neurons more susceptible to apoptotic stress. These unique actions may relate to the presence of longer, neuron-specific Bif-1 isoforms, because only these forms of Bif-1 were able to rescue deficiencies caused by Bif-1 suppression. This finding not only demonstrates an unexpected role for Bif-1 in the nervous system but this work also establishes Bif-1 as a potential therapeutic target for the treatment of neurological diseases, especially degenerative disorders characterized by alterations in mitochondrial dynamics.
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16
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Regulation of the Golgi complex by phospholipid remodeling enzymes. Biochim Biophys Acta Mol Cell Biol Lipids 2012; 1821:1078-88. [PMID: 22562055 DOI: 10.1016/j.bbalip.2012.04.004] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2011] [Revised: 03/15/2012] [Accepted: 04/13/2012] [Indexed: 11/23/2022]
Abstract
The mammalian Golgi complex is a highly dynamic organelle consisting of stacks of flattened cisternae with associated coated vesicles and membrane tubules that contribute to cargo import and export, intra-cisternal trafficking, and overall Golgi architecture. At the morphological level, all of these structures are continuously remodeled to carry out these trafficking functions. Recent advances have shown that continual phospholipid remodeling by phospholipase A (PLA) and lysophospholipid acyltransferase (LPAT) enzymes, which deacylate and reacylate Golgi phospholipids, respectively, contributes to this morphological remodeling. Here we review the identification and characterization of four cytoplasmic PLA enzymes and one integral membrane LPAT that participate in the dynamic functional organization of the Golgi complex, and how some of these enzymes are integrated to determine the relative abundance of COPI vesicle and membrane tubule formation. This article is part of a Special Issue entitled Lipids and Vesicular Transport.
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17
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Orenbuch A, Ayelet O, Shulman Y, Yoav S, Lipstein N, Noa L, Bechar A, Amit B, Lavy Y, Yotam L, Brumer E, Eliaz B, Vasileva M, Mariya V, Kahn J, Joy K, Barki-Harrington L, Liza BH, Kuner T, Thomas K, Gitler D, Daniel G. Inhibition of exocytosis or endocytosis blocks activity-dependent redistribution of synapsin. J Neurochem 2011; 120:248-58. [PMID: 22066784 DOI: 10.1111/j.1471-4159.2011.07579.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The synaptic vesicle cycle encompasses the pre-synaptic events that drive neurotransmission. Influx of calcium leads to the fusion of synaptic vesicles with the plasma membrane and the release of neurotransmitter, closely followed by endocytosis. Vacated release sites are repopulated with vesicles which are then primed for release. When activity is intense, reserve vesicles may be mobilized to counteract an eventual decline in transmission. Recently, interplay between endocytosis and repopulation of the readily releasable pool of vesicles has been identified. In this study, we show that exo-endocytosis is necessary to enable detachment of synapsin from reserve pool vesicles during synaptic activity. We report that blockage of exocytosis in cultured mouse hippocampal neurons, either by tetanus toxin or by the deletion of munc13, inhibits the activity-dependent redistribution of synapsin from the pre-synaptic terminal into the axon. Likewise, perturbation of endocytosis with dynasore or by a dynamin dominant-negative mutant fully prevents synapsin redistribution. Such inhibition of synapsin redistribution occurred despite the efficient phosphorylation of synapsin at its protein kinase A/CaMKI site, indicating that disengagement of synapsin from the vesicles requires exocytosis and endocytosis in addition to phosphorylation. Our results therefore reveal hitherto unidentified feedback within the synaptic vesicle cycle involving the synapsin-managed reserve pool.
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Affiliation(s)
- Ayelet Orenbuch
- Department of Physiology and Neurobiology, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
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18
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Cheung ZH, Ip NY. Endophilin B1: Guarding the gate to destruction. Commun Integr Biol 2011; 2:130-2. [PMID: 19704909 DOI: 10.4161/cib.7745] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2008] [Accepted: 01/02/2009] [Indexed: 11/19/2022] Open
Abstract
Endophilin B1 is a member of the endophilin family that is localized predominantly to intracellular membranes. Also known as Bax-interacting factor-1 (Bif-1), this protein has been observed to regulate the membrane dynamics of various intracellular compartments, such as the control of mitochondrial morphology and autophagosome formation in fibroblast. Endophilin B1 is expressed in the brain, but its functions in neurons had remained unknown. Recently, we have observed a novel role of endophilin B1 in neurons where it controls the trafficking of TrkA, cognate receptor for the prototypic neurotrophin nerve growth factor (NGF). Knock-down of endophilin B1 expression induces precocious targeting of NGF/TrkA to late endosomes and lysosomes, thereby leading to reduced TrkA levels. This is accompanied by marked attenuation of NGF-induced gene transcription and neurite outgrowth. Our observations suggest that endophilin B1 regulates TrkA level and downstream functions by controlling the movement of TrkA to late endosomes/lysosomes, possibly acting at the level of early endosomes.
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Affiliation(s)
- Zelda H Cheung
- Department of Biochemistry; Molecular Neuroscience Center and Biotechnology Research Institute; Hong Kong University of Science and Technology; Hong Kong, China
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19
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Cdk5-mediated phosphorylation of endophilin B1 is required for induced autophagy in models of Parkinson's disease. Nat Cell Biol 2011; 13:568-79. [PMID: 21499257 DOI: 10.1038/ncb2217] [Citation(s) in RCA: 123] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2010] [Accepted: 01/27/2011] [Indexed: 02/07/2023]
Abstract
Cyclin-dependent kinase 5 (Cdk5) is a serine/threonine kinase that is increasingly implicated in various neurodegenerative diseases. Deregulated Cdk5 activity has been associated with neuronal death, but the underlying mechanisms are not well understood. Here we report an unexpected role for Cdk5 in the regulation of induced autophagy in neurons. We have identified endophilin B1 (EndoB1) as a Cdk5 substrate, and show that Cdk5-mediated phosphorylation of EndoB1 is required for autophagy induction in starved neurons. Furthermore, phosphorylation of EndoB1 facilitates EndoB1 dimerization and recruitment of UVRAG (UV radiation resistance-associated gene). More importantly, Cdk5-mediated phosphorylation of EndoB1 is essential for autophagy induction and neuronal loss in models of Parkinson's disease. Our findings not only establish Cdk5 as a critical regulator of autophagy induction, but also reveal a role for Cdk5 and EndoB1 in the pathophysiology of Parkinson's disease through modulating autophagy.
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20
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Abstract
It has been more than 17 years since the causative mutation for Huntington's disease was discovered as the expansion of the triplet repeat in the N-terminal portion of the Huntingtin (HTT) gene. In the intervening time, researchers have discovered a great deal about Huntingtin's involvement in a number of cellular processes. However, the role of Huntingtin in the key pathogenic mechanism leading to neurodegeneration in the disease process has yet to be discovered. Here, we review the body of knowledge that has been uncovered since gene discovery and include discussions of the HTT gene, CAG triplet repeat expansion, HTT expression, protein features, posttranslational modifications, and many of its known protein functions and interactions. We also highlight potential pathogenic mechanisms that have come to light in recent years.
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Affiliation(s)
- Karen N McFarland
- Department of Neurology, University of Florida, Gainesville, FL 32610-0236, USA.
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21
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22
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Takahashi Y, Meyerkord CL, Wang HG. Bif-1/endophilin B1: a candidate for crescent driving force in autophagy. Cell Death Differ 2009; 16:947-55. [PMID: 19265852 DOI: 10.1038/cdd.2009.19] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Autophagy is an intracellular bulk degradation system that plays a vital role in maintaining cellular homeostasis. This degradation process involves dynamic membrane rearrangements resulting in the formation of double-membraned autophagosomes. However, the driving force for generating curvature and deformation of isolation membranes remains a mystery. Bax-interacting factor 1 (Bif-1), also known as SH3GLB1 or Endophilin B1, was originally discovered as a Bax-binding protein. Bif-1 contains an amino-terminal N-BAR (Bin-Amphiphysin-Rvs) domain and a carboxy-terminal SH3 (Src-homology 3) domain and shows membrane binding and bending activities. It has been shown that Beclin1 is involved in the nucleation of autophagosomal membranes through an unknown mechanism. It is interesting that, Bif-1 forms a complex with Beclin1 through ultraviolet irradiation resistant-associated gene (UVRAG) and promotes the activation of the class III PI3 kinase, Vps34, in mammalian cells. In response to nutrient starvation, Bif-1 accumulates in punctate foci where it co-localizes with LC3, Atg5, and Atg9. Furthermore, Bif-1-positive, crescent-shaped small vesicles expand by recruiting and fusing with Atg9-positive small membranes to complete autophagosome formation. This review highlights the role of Bif-1 in the regulation of autophagy and discusses the potential involvement of Bif-1 in the biogenesis of membranes for the formation of autophagosomes.
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Affiliation(s)
- Y Takahashi
- Department of Pharmacology and Penn State Hershey Cancer Institute, The Pennsylvania State University College of Medicine, Hershey, PA 17033-0850, USA
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23
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Etxebarria A, Terrones O, Yamaguchi H, Landajuela A, Landeta O, Antonsson B, Wang HG, Basañez G. Endophilin B1/Bif-1 stimulates BAX activation independently from its capacity to produce large scale membrane morphological rearrangements. J Biol Chem 2008; 284:4200-12. [PMID: 19074440 DOI: 10.1074/jbc.m808050200] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Endophilin B1/BAX-interacting factor 1 (Bif-1) is a protein that cooperates with dynamin-like protein 1 (DLP1/Drp1) to maintain normal mitochondrial outer membrane (MOM) dynamics in healthy cells and also contributes to BAX-driven MOM permeabilization (MOMP), the irreversible commitment point to cell death for the majority of apoptotic stimuli. However, despite its importance, exactly how Bif-1 fulfils its proapoptotic role is unknown. Here, we demonstrate that the stimulatory effect of Bif-1 on BAX-driven MOMP and on BAX conformational activation observed in intact cells during apoptosis can be recapitulated in a simplified system consisting of purified proteins and MOM-like liposomes. In this reconstituted model system the N-BAR domain of Bif-1 reproduced the stimulatory effect of Bif-1 on functional BAX activation. This process was dependent on physical interaction between Bif-1 N-BAR and BAX as well as on the presence of the mitochondrion-specific lipid cardiolipin. Despite that Bif-1 N-BAR produced large scale morphological rearrangements in MOM-like liposomes, this phenomenon could be separated from functional BAX activation. Furthermore, DLP1 also caused global morphological changes in MOM-like liposomes, but DLP1 did not stimulate BAX-permeabilizing function in the absence or presence of Bif-1. Taken together, our findings not only provide direct evidence for a functional interplay between Bif-1, BAX, and cardiolipin during MOMP but also add significantly to the growing body of evidence indicating that components of the mitochondrial morphogenesis machinery possess proapoptotic functions that are independent from their recognized roles in normal mitochondrial dynamics.
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Affiliation(s)
- Aitor Etxebarria
- Unidad de Biofísica, Centro Mixto Consejo Superior de Investigaciones Cientificas, Universidad del Pais Vasco/Euskal Herriko Unibertsitatea, 48080 Bilbao, Spain
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24
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Endophilin B1 as a novel regulator of nerve growth factor/ TrkA trafficking and neurite outgrowth. J Neurosci 2008; 28:9002-12. [PMID: 18768694 DOI: 10.1523/jneurosci.0767-08.2008] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Neurotrophins and their cognate receptors Trks are important regulators of neuronal survival and differentiation. Recent studies reveal that internalization and trafficking of Trks play a critical role in neurotrophin-mediated signaling. At present, little is known of the molecular events that mediate this process. In the current study, we show that endophilin B1 is a novel regulator of nerve growth factor (NGF) trafficking. We found that endophilin B1 interacts with both TrkA and early endosome marker EEA1. Interestingly, knockdown of endophilin B1 results in enlarged EEA1-positive vesicles in NGF-treated PC12 cells. This is accompanied by increased lysosomal targeting of NGF/TrkA and TrkA degradation, and reduced total TrkA levels. In addition, knockdown of endophilin B1 attenuates Erk1/2 activation in the endosomal fraction after NGF treatment. This is accompanied by a marked inhibition of NGF-induced gene transcription and neurite outgrowth in endophilin B1-knocked down cells. Our observations implicate endophilin B1 as a novel regulator of NGF trafficking, thereby affecting TrkA levels and downstream signaling on endosomes to mediate biological functions of NGF.
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25
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Prendergast GC, Muller AJ, Ramalingam A, Chang MY. BAR the door: cancer suppression by amphiphysin-like genes. Biochim Biophys Acta Rev Cancer 2008; 1795:25-36. [PMID: 18930786 DOI: 10.1016/j.bbcan.2008.09.001] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2008] [Revised: 08/26/2008] [Accepted: 09/03/2008] [Indexed: 11/17/2022]
Abstract
The evolutionarily conserved amphiphysin-like genes Bin1 and Bin3 function in membrane and actin dynamics, cell polarity, and stress signaling. Recent genetic studies in mice discriminate non-essential roles in endocytic processes commonly ascribed to amphiphysins from essential roles in cancer suppression. Bin1 acts in default pathways of apoptosis and senescence that are triggered by the Myc and Raf oncogenes in primary cells, and Bin1 gene products display a 'moonlighting function' in the nucleus where a variety of other 'endocytic' proteins are also found. Together, genetic investigations in yeast, flies, and mice suggest that amphiphysin-like adapter proteins may suppress cancer by helping integrate cell polarity signals generated by actin and vesicle dynamics with central regulators of cell cycle arrest, apoptosis, and immune surveillance.
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Le HY, Zhang Y, Liu H, Ma LH, Jin Y, Huang QH, Chen Y, Deng M, Chen Z, Chen SJ, Liu TX. eena Promotes Myeloid Proliferation through Stimulating ERK1/2 Phosphorylation in Zebrafish. J Biol Chem 2008; 283:17652-61. [DOI: 10.1074/jbc.m710517200] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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27
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Hrabchak C, Henderson H, Varmuza S. A Testis Specific Isoform of Endophilin B1, Endophilin B1t, Interacts Specifically with Protein Phosphatase-1cγ2 in Mouse Testis and Is Abnormally Expressed in PP1cγ Null Mice. Biochemistry 2007; 46:4635-44. [PMID: 17381077 DOI: 10.1021/bi6025837] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Male mice homozygous for a null mutation in the protein phosphatase-1c gamma (PP1c gamma) gene are infertile, displaying a severe impairment in spermatogenesis that is not compensated by the presence of PP1c alpha and PP1c beta in mutant testes. A lack of the PP1c gamma2 splice variant seems the most likely cause of the mutant phenotype, as it is the most heavily expressed PP1c gamma isoform in wild type testes. Yeast two-hybrid screening using PP1c gamma2 has identified several new binding partners, including endophilin B1t, a testis enriched isoform of endophilin B1a which differs from the somatic form by virtue of a carboxy terminal deletion spanning the last 10 amino acids. The testis isoform did not show an interaction with PP1c alpha, or with a truncated PP1c gamma2 mutant lacking the unique carboxy terminus. In contrast, somatic endophilin B1a did not interact with any of the PP1c isoforms. Sedimentation and co-immunoprecipitation experiments using native testis proteins verified binding of endophilin B1t to PP1c gamma2. Immunohistochemistry on wild type testis sections revealed a stage specific expression pattern for endophilin that appeared concentrated at discrete puncta throughout the seminiferous epithelium. Punctate endophilin expression in cells adjacent to the lumen was absent in PP1c gamma null mice. Phosphatase assays indicate that chimeric endophilin B1t is able to inhibit recombinant PP1c gamma2 activity toward phosphorylase a while having little effect on the activity of PP1c alpha. A potential role for endophilin B1t in mammalian spermatogenesis is discussed within the context of the PP1c gamma knockout testis phenotype.
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Affiliation(s)
- Christopher Hrabchak
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
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28
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McNiven MA, Thompson HM. Vesicle formation at the plasma membrane and trans-Golgi network: the same but different. Science 2006; 313:1591-4. [PMID: 16973870 DOI: 10.1126/science.1118133] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
An elaborate vesicle transport system supports the active exchange of membranes and protein cargo between the plasma membrane and the trans-Golgi network. Many observations suggest that highly conserved mechanisms are used in vesicle formation and scission. Such similarity is found both at the level of the receptor-ligand sequestration process that uses clathrin and associated polymeric and monomeric adaptor proteins, and in the machinery used to deform and vesiculate lipid membranes.
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Affiliation(s)
- Mark A McNiven
- Department of Biochemistry and Molecular Biology and the Miles and Shirley Fiterman Center for Digestive Diseases, Mayo Clinic College of Medicine, Rochester, MN 55905, USA.
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29
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Abstract
Mitochondria are key players in several cellular functions including growth, division, energy metabolism, and apoptosis. The mitochondrial network undergoes constant remodelling and these morphological changes are of direct relevance for the role of this organelle in cell physiology. Mitochondrial dysfunction contributes to a number of human disorders and may aid cancer progression. Here, we summarize the recent contributions made in the field of mitochondrial dynamics and discuss their impact on our understanding of cell function and tumorigenesis.
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Affiliation(s)
- E Alirol
- Department of Cell Biology, University of Geneva, Genève, Switzerland
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30
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Masuda M, Takeda S, Sone M, Ohki T, Mori H, Kamioka Y, Mochizuki N. Endophilin BAR domain drives membrane curvature by two newly identified structure-based mechanisms. EMBO J 2006; 25:2889-97. [PMID: 16763557 PMCID: PMC1500852 DOI: 10.1038/sj.emboj.7601176] [Citation(s) in RCA: 215] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2005] [Accepted: 05/08/2006] [Indexed: 11/09/2022] Open
Abstract
The crescent-shaped BAR (Bin/Amphiphysin/Rvs-homology) domain dimer is a versatile protein module that senses and generates positive membrane curvature. The BAR domain dimer of human endophilin-A1, solved at 3.1 A, has a unique structure consisting of a pair of helix-loop appendages sprouting out from the crescent. The appendage's short helices form a hydrophobic ridge, which runs across the concave surface at its center. Examining liposome binding and tubulation in vitro using purified BAR domain and its mutants indicated that the ridge penetrates into the membrane bilayer and enhances liposome tubulation. BAR domain-expressing cells exhibited marked plasma membrane tubulation in vivo. Furthermore, a swinging-arm mutant lost liposome tubulation activity yet retaining liposome binding. These data suggested that the rigid crescent dimer shape is crucial for the tubulation. We here propose that the BAR domain drives membrane curvature by coordinate action of the crescent's scaffold mechanism and the ridge's membrane insertion in addition to membrane binding via amino-terminal amphipathic helix.
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Affiliation(s)
- Michitaka Masuda
- Department of Structural Analysis, National Cardiovascular Center Research Institute, Suita, Osaka, Japan
| | - Soichi Takeda
- Department of Cardiac Physiology, National Cardiovascular Center Research Institute, Suita, Osaka, Japan
- Laboratory of structural biochemistry, RIKEN Harima Institute at SPring-8, Mikazuki-cho, Sayo, Hyogo, Japan
| | - Manami Sone
- Department of Structural Analysis, National Cardiovascular Center Research Institute, Suita, Osaka, Japan
| | - Takashi Ohki
- Department of Structural Analysis, National Cardiovascular Center Research Institute, Suita, Osaka, Japan
| | - Hidezo Mori
- Department of Cardiac Physiology, National Cardiovascular Center Research Institute, Suita, Osaka, Japan
| | - Yuji Kamioka
- Department of Structural Analysis, National Cardiovascular Center Research Institute, Suita, Osaka, Japan
| | - Naoki Mochizuki
- Department of Structural Analysis, National Cardiovascular Center Research Institute, Suita, Osaka, Japan
- Department of Structural Analysis, National Cardiovascular Center Research Institute, 5-7-1 Fujishiro-dai, Suita, Osaka 565-8565, Japan. Tel.: +81 6 6833 5012; Fax: +81 6 6835 5461; E-mail:
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31
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Parone PA, Martinou JC. Mitochondrial fission and apoptosis: an ongoing trial. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2006; 1763:522-30. [PMID: 16762428 DOI: 10.1016/j.bbamcr.2006.04.005] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2006] [Revised: 04/11/2006] [Accepted: 04/13/2006] [Indexed: 12/26/2022]
Abstract
Apoptosis is a form of programmed cell death that is essential for the development and tissue homeostasis in all metazoan animals. Mitochondria play a critical role during apoptosis, since the release of pro-apoptogenic proteins from the organelle is a pivotal event in cell death triggered by many cytotoxic stimuli. A striking morphological change occurring during apoptosis is the disintegration of the semi-reticular mitochondrial network into small punctiform organelles. It is only recently that this event has been shown to require the activity of proteins involved in the physiological processes of mitochondrial fission and fusion. Here, we discuss how this mitochondrial morphological transition occurs during cell death and the role that it may have in apoptosis.
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Affiliation(s)
- Philippe A Parone
- Department of Cell Biology, University of Geneva, Quai Ernest-Ansermet 30, 1211 Geneva 4, Switzerland
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32
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Ren G, Vajjhala P, Lee JS, Winsor B, Munn AL. The BAR domain proteins: molding membranes in fission, fusion, and phagy. Microbiol Mol Biol Rev 2006; 70:37-120. [PMID: 16524918 PMCID: PMC1393252 DOI: 10.1128/mmbr.70.1.37-120.2006] [Citation(s) in RCA: 147] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The Bin1/amphiphysin/Rvs167 (BAR) domain proteins are a ubiquitous protein family. Genes encoding members of this family have not yet been found in the genomes of prokaryotes, but within eukaryotes, BAR domain proteins are found universally from unicellular eukaryotes such as yeast through to plants, insects, and vertebrates. BAR domain proteins share an N-terminal BAR domain with a high propensity to adopt alpha-helical structure and engage in coiled-coil interactions with other proteins. BAR domain proteins are implicated in processes as fundamental and diverse as fission of synaptic vesicles, cell polarity, endocytosis, regulation of the actin cytoskeleton, transcriptional repression, cell-cell fusion, signal transduction, apoptosis, secretory vesicle fusion, excitation-contraction coupling, learning and memory, tissue differentiation, ion flux across membranes, and tumor suppression. What has been lacking is a molecular understanding of the role of the BAR domain protein in each process. The three-dimensional structure of the BAR domain has now been determined and valuable insight has been gained in understanding the interactions of BAR domains with membranes. The cellular roles of BAR domain proteins, characterized over the past decade in cells as distinct as yeasts, neurons, and myocytes, can now be understood in terms of a fundamental molecular function of all BAR domain proteins: to sense membrane curvature, to bind GTPases, and to mold a diversity of cellular membranes.
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Affiliation(s)
- Gang Ren
- Institute for Molecular Bioscience, University of Queensland, St. Lucia, Queensland 4072, Australia
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33
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Gallop JL, Butler PJG, McMahon HT. Endophilin and CtBP/BARS are not acyl transferases in endocytosis or Golgi fission. Nature 2005; 438:675-8. [PMID: 16319893 DOI: 10.1038/nature04136] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2005] [Accepted: 08/15/2005] [Indexed: 11/08/2022]
Abstract
Endophilins have been proposed to have an enzymatic activity (a lysophosphatidic acid acyl transferase or LPAAT activity) that can make phosphatidic acid in membranes. This activity is thought to change the bilayer asymmetry in such a way that negative membrane curvature at the neck of a budding vesicle will be stabilized. An LPAAT activity has also been proposed for CtBP/BARS (carboxy-terminal binding protein/brefeldin A-ribosylated substrate), a transcription co-repressor that is implicated in dynamin-independent endocytosis and fission of the Golgi in mitosis. Here we show that the LPAAT activity associated with endophilin is a contaminant of the purification procedure and can be also found associated with the pleckstrin homology domain of dynamin. Likewise, the LPAAT activity associated with CtBP/BARS is also a co-purification artefact. The proposed locus of activity in endophilins includes the BAR domain, which has no catalytic site but instead senses positive membrane curvature. These data will prompt a re-evaluation of the molecular details of membrane budding.
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Affiliation(s)
- Jennifer L Gallop
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK
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34
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Takahashi Y, Karbowski M, Yamaguchi H, Kazi A, Wu J, Sebti SM, Youle RJ, Wang HG. Loss of Bif-1 suppresses Bax/Bak conformational change and mitochondrial apoptosis. Mol Cell Biol 2005; 25:9369-82. [PMID: 16227588 PMCID: PMC1265816 DOI: 10.1128/mcb.25.21.9369-9382.2005] [Citation(s) in RCA: 144] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2005] [Revised: 06/07/2005] [Accepted: 08/02/2005] [Indexed: 11/20/2022] Open
Abstract
Bif-1, a member of the endophilin B protein family, interacts with Bax and promotes interleukin-3 withdrawal-induced Bax conformational change and apoptosis when overexpressed in FL5.12 cells. Here, we provide evidence that Bif-1 plays a regulatory role in apoptotic activation of not only Bax but also Bak and appears to be involved in suppression of tumorigenesis. Inhibition of endogenous Bif-1 expression in HeLa cells by RNA interference abrogated the conformational change of Bax and Bak, cytochrome c release, and caspase 3 activation induced by various intrinsic death signals. Similar results were obtained in Bif-1 knockout mouse embryonic fibroblasts. While Bif-1 did not directly interact with Bak, it heterodimerized with Bax on mitochondria in intact cells, and this interaction was enhanced by apoptosis induction and preceded the Bax conformational change. Moreover, suppression of Bif-1 expression was associated with an enhanced ability of HeLa cells to form colonies in soft agar and tumors in nude mice. Taken together, these findings support the notion that Bif-1 is an important component of the mitochondrial pathway for apoptosis as a novel Bax/Bak activator, and loss of this proapoptotic molecule may contribute to tumorigenesis.
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Affiliation(s)
- Yoshinori Takahashi
- Drug Discovery Program, H. Lee Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, FL 33612, USA
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35
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Lucken-Ardjomande S, Martinou JC. Regulation of Bcl-2 proteins and of the permeability of the outer mitochondrial membrane. C R Biol 2005; 328:616-31. [PMID: 15992745 DOI: 10.1016/j.crvi.2005.05.002] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2005] [Accepted: 05/03/2005] [Indexed: 12/12/2022]
Abstract
In many apoptotic responses, pro-apoptotic members of the Bcl-2 family trigger the permeabilization of the outer mitochondrial membrane, thereby allowing the release of mitochondrial apoptogenic factors that contribute to caspase activation in the cytosol. The mechanisms that lead to the activation of pro-apoptotic Bcl-2 family members and to the permeabilization of the outer mitochondrial membrane are not yet completely understood. Here, we attempt to summarize our current view of the mechanisms that lead to these events, regarding both additional proteins that were recently suggested to be involved, and the roles of lipids.
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Affiliation(s)
- Safa Lucken-Ardjomande
- Department of Cell Biology, University of Geneva, 30, quai Ernest-Ansermet, 1211 Genève 4, Switzerland
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36
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Lucken-Ardjomande S, Martinou JC. Newcomers in the process of mitochondrial permeabilization. J Cell Sci 2005; 118:473-83. [PMID: 15673686 DOI: 10.1242/jcs.01654] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Under stress conditions, apoptogenic factors normally sequestered in the mitochondrial intermembrane space are released into the cytosol, caspases are activated and cells die by apoptosis. Although the precise mechanism that leads to the permeabilization of mitochondria is still unclear, the activation of multidomain pro-apoptotic proteins of the Bcl-2 family, such as Bax and Bak, is evidently crucial. Regulation of Bax and Bak by other members of the family has been known for a long time, but recent evidence suggests that additional unrelated proteins participate in the process, both as inhibitors and activators. The important rearrangements mitochondrial lipids undergo during apoptosis play a role in the permeabilization process and this role is probably more central than first envisioned.
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Affiliation(s)
- Safa Lucken-Ardjomande
- Department of Cell Biology, University of Geneva, 30 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
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37
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Ralser M, Nonhoff U, Albrecht M, Lengauer T, Wanker EE, Lehrach H, Krobitsch S. Ataxin-2 and huntingtin interact with endophilin-A complexes to function in plastin-associated pathways. Hum Mol Genet 2005; 14:2893-909. [PMID: 16115810 DOI: 10.1093/hmg/ddi321] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Spinocerebellar ataxia type 2 is an inherited neurodegenerative disorder that is caused by an expanded trinucleotide repeat in the SCA2 gene, encoding a polyglutamine stretch in the gene product ataxin-2. Although evidence has been provided that ataxin-2 is involved in RNA metabolism, the physiological function of ataxin-2 remains unclear. Here, we demonstrate that ataxin-2 interacts with two members of the endophilin family, endophilin-A1 and endophilin-A3. To elucidate the physiological implications of these interactions, we exploited yeast as a model system and discovered that expression of ataxin-2 as well as both endophilin proteins is toxic for yeast lacking the SAC6 gene product fimbrin, a protein involved in actin filament organization and endocytotic processes. Intriguingly, expression of huntingtin, another polyglutamine protein interacting with endophilin-A3, was also toxic in Deltasac6 yeast. These effects can be suppressed by simultaneous expression of one of the two human fimbrin orthologs, L- or T-plastin. Moreover, we have discovered that ataxin-2 associates with L- and T-plastin and that overexpression of ataxin-2 leads to accumulation of T-plastin in mammalian cells. Thus, our findings suggest an interplay between ataxin-2, endophilin proteins and huntingtin in plastin-associated cellular pathways.
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Affiliation(s)
- Markus Ralser
- Max Planck Institute for Molecular Genetics, Ihnestrasse 73, 14195 Berlin, Germany
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38
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Lua BL, Low BC. Activation of EGF receptor endocytosis and ERK1/2 signaling by BPGAP1 requires direct interaction with EEN/endophilin II and a functional RhoGAP domain. J Cell Sci 2005; 118:2707-21. [PMID: 15944398 DOI: 10.1242/jcs.02383] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Rho GTPases are important regulators for cell dynamics. They are activated by guanine nucleotide exchange factors and inactivated by GTPase-activating proteins (GAPs). We recently identified a novel RhoGAP, BPGAP1, that uses the BNIP-2 and Cdc42GAP homology (BCH) domain, RhoGAP domain and proline-rich region to regulate cell morphology and migration. To further explore its roles in intracellular signaling, we employed protein precipitations and matrix-assisted laser desorption/ionization mass-spectrometry and identified EEN/endophilin II as a novel partner of BPGAP1. EEN is a member of the endocytic endophilin family but its function in regulating endocytosis remains unclear. Pull-down and co-immunoprecipitation studies with deletion mutants confirmed that EEN interacted directly with BPGAP1 via its Src homology 3 (SH3) domain binding to the proline-rich region 182-PPPRPPLP-189 of BPGAP1, with prolines 184 and 186 being indispensable for this interaction. Overexpression of EEN or BPGAP1 alone induced EGF-stimulated receptor endocytosis and ERK1/2 phosphorylation. These processes were further enhanced when EEN was present together with the wildtype but not with the non-interactive proline mutant of BPGAP1. However, EEN lacking the SH3 domain served as a dominant negative mutant that completely inhibited these effects. Furthermore, BPGAP1 with a catalytically inactive GAP domain also blocked the effect of EEN and/or BPGAP1 in EGF receptor endocytosis and concomitantly reduced their level of augmentation for ERK1/2 phosphorylation. Our findings reveal a concomitant activation of endocytosis and ERK signaling by BPGAP1 via the coupling of its proline-rich region, which targets EEN and its functional GAP domain. BPGAP1 could therefore provide an important link between cytoskeletal network, endocytic trafficking and Ras/MAPK signaling.
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Affiliation(s)
- Bee Leng Lua
- Cell Signaling and Developmental Biology Laboratory, Department of Biological Sciences, The National University of Singapore
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Yao J, Ren X, Ireland JJ, Coussens PM, Smith TPL, Smith GW. Generation of a bovine oocyte cDNA library and microarray: resources for identification of genes important for follicular development and early embryogenesis. Physiol Genomics 2005; 19:84-92. [PMID: 15375196 DOI: 10.1152/physiolgenomics.00123.2004] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The oocyte is a key regulator of ovarian folliculogenesis and early embryonic development. However, the composition of the oocyte transcriptome and identities and functions of key oocyte-specific genes involved in the above processes are relatively unknown. Using a PCR-based cDNA amplification method (SMART technology), we constructed a bovine oocyte cDNA library. Analysis of 230 expressed sequence tags (ESTs) from this library identified 102 unique sequences. Although some correspond to housekeeping genes (e.g., ribosomal protein L15) and some represent genes previously known to be expressed in oocytes and other tissues, most encode for genes whose expression in mammalian oocytes has not been reported previously (e.g., cocaine- and amphetamine-regulated transcript) or genes of unknown function. Sixteen did not show significant sequence similarity to any entries in the GenBank database and were classified as novel. Using over 2,000 unsequenced, randomly selected cDNA clones from the library, we constructed an oocyte microarray and performed experiments to identify genes preferentially expressed in fetal ovary (an enriched source of oocytes) relative to somatic tissues. Eleven clones were identified by microarray analysis with consistently higher expression in fetal ovaries (collected from animals at days 210-260 of gestation) compared with spleen and liver. DNA sequence analysis of these clones revealed that two correspond to JY-1, a novel bovine oocyte-specific gene. The remaining nine clones represent five identified genes and one additional completely novel gene. Increased abundance of mRNA in fetal ovary for five of the six genes identified was confirmed by real-time PCR. Results demonstrate the potential utility of these unique resources for identification of oocyte-expressed genes potentially important for reproductive function.
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Affiliation(s)
- Jianbo Yao
- Division of Animal and Veterinary Sciences, West Virginia University, Morgantown, West Virginia 26506-6108, USA.
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Abstract
Membrane vesicle cycling is orchestrated through the combined actions of proteins and lipids. At neuronal synapses, this orchestration must meet the stringent demands of speed, fidelity and sustainability of the synaptic vesicle cycle that mediates neurotransmission. Historically, the lion's share of the attention has been focused on the proteins that are involved in this cycle; but, in recent years, it has become clear that the previously unheralded plasma membrane and vesicle lipids are also key regulators of this cycle. This article reviews recent insights into the roles of lipid-modifying enzymes and lipids in the acute modulation of neurotransmission.
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Affiliation(s)
- Jeffrey Rohrbough
- Department of Biological Sciences, Vanderbilt Kennedy Center for Research on Human Development, Vanderbilt University, Nashville, Tennessee 37235-1634, USA
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41
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Abstract
Lipids were long considered to be passive passengers of carrier vesicles with the single role of sealing the transport container. We now know that specific phospholipids are required for efficient fusion, while others facilitate budding and fission. Moreover, the various polyphosphoinositides assist in the recruitment from the cytosol of proteins of the transport machinery. Finally, the segregation of membrane lipids into different fluid phases appears to serve as a 'lipid raft' mechanism for protein sorting at various stages of the secretory and endocytic pathways. The current challenge is to understand how proteins control the metabolism and subcellular localization, and thereby the activity, of the various lipids.
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Affiliation(s)
- Gerrit van Meer
- Department of Membrane Enzymology, Centre for Biomembranes and Lipid Enzymology, Institute of Biomembranes, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
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42
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Hughes AC, Errington R, Fricker-Gates R, Jones L. Endophilin A3 forms filamentous structures that colocalise with microtubules but not with actin filaments. ACTA ACUST UNITED AC 2004; 128:182-92. [PMID: 15363893 DOI: 10.1016/j.molbrainres.2004.06.016] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/14/2004] [Indexed: 11/20/2022]
Abstract
Endophilin A3 is a member of the endophilin family of proteins, thought to play a role in the formation of clathrin-coated vesicles from the plasma membrane in the process of clathrin-mediated endocytosis. We investigated the localisation of both endogenous and overexpressed endophilin A3 within mammalian cells. Endophilin A3 demonstrated a complex cellular distribution with bright punctate structures and filamentous strands superimposed on a diffuse cytoplasmic background. The endophilin A3 structures did not colocalise with mitochondria, endoplasmic reticulum or lysosomes. Direct immunolocalisation and cytoskeletal perturbation studies showed that the filamentous structures were more likely to be colocalised with microtubules than actin filaments. We therefore propose that endophilin A3 has a role in transport along or as part of the structure of microtubules, in addition to its suggested role in endocytosis.
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Affiliation(s)
- Alis C Hughes
- Institute of Medical Genetics, University of Wales College of Medicine, Heath Park, Cardiff CF14 4XN, UK
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43
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Richnau N, Fransson A, Farsad K, Aspenström P. RICH-1 has a BIN/Amphiphysin/Rvsp domain responsible for binding to membrane lipids and tubulation of liposomes. Biochem Biophys Res Commun 2004; 320:1034-42. [PMID: 15240152 DOI: 10.1016/j.bbrc.2004.05.221] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2004] [Indexed: 11/27/2022]
Abstract
RhoGAP interacting with CIP4 homologs-1 (RICH-1) was previously found in a yeast two-hybrid screen for proteins interacting with the SH3 domain of the Cdc42-interacting protein 4 (CIP4). RICH-1 was shown to be a RhoGAP for Cdc42 and Rac. In this study, we show that the BIN/Amphiphysin/Rvsp (BAR) domain in RICH-1 confers binding to membrane lipids, and has the potential to deform spherical liposomes into tubes. In accordance with previous findings for the BAR domains in endophilin and amphiphysin, RICH-1-induced tubes appeared striated. We propose that these striated structures are formed by oligomerization of RICH-1 through a putative coiled-coil region within the BAR domain. In support of this notion, we show that RICH-1 forms oligomers in the presence of the chemical cross-linker BS3. These results point to an involvement of RICH-1 in membrane deformation events.
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Affiliation(s)
- Ninna Richnau
- Ludwig Institute for Cancer Research, Box 595, Biomedical Center, 751 24 Uppsala, Sweden
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44
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Sugiura H, Iwata K, Matsuoka M, Hayashi H, Takemiya T, Yasuda S, Ichikawa M, Yamauchi T, Mehlen P, Haga T, Yamagata K. Inhibitory Role of Endophilin 3 in Receptor-mediated Endocytosis. J Biol Chem 2004; 279:23343-8. [PMID: 15066995 DOI: 10.1074/jbc.m312607200] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Endophilin 1 (Endo1) participates in synaptic vesicle biogenesis through interactions of its Src homology 3 domain with the polyphosphoinositide phosphatase Synaptojanin and the GTPase Dynamin. Endo1 has also been reported to affect endocytosis by converting membrane curvature via its lysophosphatidic acid acyltransferase activity. Here we report that a closely related isoform of Endo1, Endo3, inhibits clathrin-mediated endocytosis. Mutational analyses showed that the variable region of Endo3 is important in regulating transferrin endocytosis. In the brain, Endo3 is co-localized with dopamine D2 receptor in olfactory nerve terminals and inhibits its clathrin-mediated endocytosis in COS-7 cells. Furthermore, overexpression of Endo3 in an olfactory epithelium-derived cell line suppressed dopamine D2 receptor-mediated endocytosis and therefore accelerated its dopamine-induced differentiation. These results indicate that Endo3 may act as a negative regulator of clathrin-mediated endocytosis in brain neurons.
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Affiliation(s)
- Hiroko Sugiura
- Department of Neuropharmacology, Tokyo Metropolitan Institute for Neuroscience, Fuchu, Tokyo 183-8526, Japan
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45
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Affiliation(s)
- Gabor Tigyi
- Department of Physiology, The University of Tennessee Health Science Center, Memphis, TN 38163, USA.
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46
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Sarret P, Esdaile MJ, McPherson PS, Schonbrunn A, Kreienkamp HJ, Beaudet A. Role of Amphiphysin II in Somatostatin Receptor Trafficking in Neuroendocrine Cells. J Biol Chem 2004; 279:8029-37. [PMID: 14660576 DOI: 10.1074/jbc.m310792200] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Amphiphysins are SH3 domain-containing proteins thought to function in clathrin-mediated endocytosis. To investigate the potential role of amphiphysin II in cellular trafficking of G protein-coupled somatostatin (SRIF) receptors, we generated an AtT-20 cell line stably overexpressing amphiphysin IIb, a splice variant that does not bind clathrin. Endocytosis of (125)I-[d-Trp(8)]SRIF was not affected by amphiphysin IIb overexpression. However, the maximal binding capacity (B(max)) of the ligand on intact cells was significantly lower in amphiphysin IIb overexpressing than in non-transfected cells. This difference was no longer apparent when the experiments were performed on crude cell homogenates, suggesting that amphiphysin IIb overexpression interferes with SRIF receptor targeting to the cell surface and not with receptor synthesis. Accordingly, immunofluorescence experiments demonstrated that, in amphiphysin overexpressing cells, sst(2A) and sst(5) receptors were segregated in a juxtanuclear compartment identified as the trans-Golgi network. Amphiphysin IIb overexpression had no effect on corticotrophin-releasing factor 41-stimulated adrenocorticotropic hormone secretion, suggesting that it is not involved in the regulated secretory pathway. Taken together, these results suggest that amphiphysin II is not necessary for SRIF receptor endocytosis but is critical for its constitutive targeting to the plasma membrane. Therefore, amphiphysin IIb may be an important component of the constitutive secretory pathway.
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Affiliation(s)
- Philippe Sarret
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec H3A 2B4, Canada
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47
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Schuske KR, Richmond JE, Matthies DS, Davis WS, Runz S, Rube DA, van der Bliek AM, Jorgensen EM. Endophilin is required for synaptic vesicle endocytosis by localizing synaptojanin. Neuron 2004; 40:749-62. [PMID: 14622579 DOI: 10.1016/s0896-6273(03)00667-6] [Citation(s) in RCA: 202] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Endophilin is a membrane-associated protein required for endocytosis of synaptic vesicles. Two models have been proposed for endophilin: that it alters lipid composition in order to shape membranes during endocytosis, or that it binds the polyphosphoinositide phosphatase synaptojanin and recruits this phosphatase to membranes. In this study, we demonstrate that the unc-57 gene encodes the Caenorhabditis elegans ortholog of endophilin A. We demonstrate that endophilin is required in C. elegans for synaptic vesicle recycling. Furthermore, the defects observed in endophilin mutants closely resemble those observed in synaptojanin mutants. The electrophysiological phenotype of endophilin and synaptojanin double mutants are virtually identical to the single mutants, demonstrating that endophilin and synaptojanin function in the same pathway. Finally, endophilin is required to stabilize expression of synaptojanin at the synapse. These data suggest that endophilin is an adaptor protein required to localize and stabilize synaptojanin at membranes during synaptic vesicle recycling.
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Affiliation(s)
- Kimberly R Schuske
- Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, UT 84112, USA
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48
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Peter BJ, Kent HM, Mills IG, Vallis Y, Butler PJG, Evans PR, McMahon HT. BAR domains as sensors of membrane curvature: the amphiphysin BAR structure. Science 2003; 303:495-9. [PMID: 14645856 DOI: 10.1126/science.1092586] [Citation(s) in RCA: 1308] [Impact Index Per Article: 62.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The BAR (Bin/amphiphysin/Rvs) domain is the most conserved feature in amphiphysins from yeast to human and is also found in endophilins and nadrins. We solved the structure of the Drosophila amphiphysin BAR domain. It is a crescent-shaped dimer that binds preferentially to highly curved negatively charged membranes. With its N-terminal amphipathic helix and BAR domain (N-BAR), amphiphysin can drive membrane curvature in vitro and in vivo. The structure is similar to that of arfaptin2, which we find also binds and tubulates membranes. From this, we predict that BAR domains are in many protein families, including sorting nexins, centaurins, and oligophrenins. The universal and minimal BAR domain is a dimerization, membrane-binding, and curvature-sensing module.
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Affiliation(s)
- Brian J Peter
- Medical Research Council (MRC) Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK
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49
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Abstract
Huntington's disease (HD) is caused by a polyglutamine expansion in the protein huntingtin. In its terminal stage, HD is characterized by widespread neuronal death in the neocortex and the striatum. Classically, this neuronal death has been thought to underlie most of the symptoms of the disease. Accumulating evidence suggests, however, that cellular dysfunction is important in the pathogenesis of HD. We propose that specific impairment of the exocytosis and endocytosis machinery contributes to the development of HD. We also suggest that abnormal synaptic transmission underlies the early symptoms of HD and can contribute to the triggering of cell death in later stages of the disease.
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Affiliation(s)
- Jia-Yi Li
- Section for Neuronal Survival, Wallenberg Neuroscience Center, Lund University, BMC A10, 221 84, Lund, Sweden
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50
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Abstract
Membrane traffic requires the generation of high-curvature lipid-bound transport carriers represented by tubules and vesicles. The mechanisms through which membranes are deformed has gained much recent attention. A major advance has been the demonstration that direct interactions between cytosolic proteins and lipid bilayers are important in the acquisition of membrane curvature. Rather than being driven only by the formation of membrane-associated structural scaffolds, membrane deformation requires physical perturbation of the lipid bilayer. A variety of proteins have been identified that directly bind and deform membranes. An emerging theme in this process is the importance of amphipathic peptides that partially penetrate the lipid bilayer.
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Affiliation(s)
- Khashayar Farsad
- Department of Cell Biology, Howard Hughes Medical Institute, Boyer Center for Molecular Medicine, Yale University School of Medicine, 295 Congress Avenue, New Haven, CT 06510, USA
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