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Patnaik SR, Zhang X, Biswas L, Akhtar S, Zhou X, Kusuluri DK, Reilly J, May-Simera H, Chalmers S, McCarron JG, Shu X. RPGR protein complex regulates proteasome activity and mediates store-operated calcium entry. Oncotarget 2018; 9:23183-23197. [PMID: 29796181 PMCID: PMC5955404 DOI: 10.18632/oncotarget.25259] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Accepted: 04/07/2018] [Indexed: 11/25/2022] Open
Abstract
Ciliopathies are a group of genetically heterogeneous disorders, characterized by defects in cilia genesis or maintenance. Mutations in the RPGR gene and its interacting partners, RPGRIP1 and RPGRIP1L, cause ciliopathies, but the function of their proteins remains unclear. Here we show that knockdown (KD) of RPGR, RPGRIP1 or RPGRIP1L in hTERT-RPE1 cells results in abnormal actin cytoskeleton organization. The actin cytoskeleton rearrangement is regulated by the small GTPase RhoA via the planar cell polarity (PCP) pathway. RhoA activity was upregulated in the absence of RPGR, RPGRIP1 or RPGRIP1L proteins. In RPGR, RPGRIP1 or RPGRIP1L KD cells, we observed increased levels of DVl2 and DVl3 proteins, the core components of the PCP pathway, due to impaired proteasomal activity. RPGR, RPGRIP1 or RPGRIP1L KD cells treated with thapsigargin (TG), an inhibitor of sarcoendoplasmic reticulum Ca2+- ATPases, showed impaired store-operated Ca2+ entry (SOCE), which is mediated by STIM1 and Orai1 proteins. STIM1 was not localized to the ER-PM junction upon ER store depletion in RPGR, RPGRIP1 or RPGRIP1L KD cells. Our results demonstrate that the RPGR protein complex is required for regulating proteasomal activity and for modulating SOCE, which may contribute to the ciliopathy phenotype.
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Affiliation(s)
- Sarita Rani Patnaik
- Department of Life Sciences, Glasgow Caledonian University, Glasgow G4 0BA, Scotland
- Institute of Molecular Physiology, Johannes Gutenberg-Universität Mainz, D-55128 Mainz, Germany
| | - Xun Zhang
- Department of Life Sciences, Glasgow Caledonian University, Glasgow G4 0BA, Scotland
| | - Lincoln Biswas
- Department of Life Sciences, Glasgow Caledonian University, Glasgow G4 0BA, Scotland
| | - Saeed Akhtar
- Cornea Research Chair, Department of Optometry, King Saud University, Riyadh 11433, Kingdom of Saudi Arabia
| | - Xinzhi Zhou
- Department of Life Sciences, Glasgow Caledonian University, Glasgow G4 0BA, Scotland
| | - Deva Krupakar Kusuluri
- Institute of Molecular Physiology, Johannes Gutenberg-Universität Mainz, D-55128 Mainz, Germany
| | - James Reilly
- Department of Life Sciences, Glasgow Caledonian University, Glasgow G4 0BA, Scotland
| | - Helen May-Simera
- Institute of Molecular Physiology, Johannes Gutenberg-Universität Mainz, D-55128 Mainz, Germany
| | - Susan Chalmers
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow G4 0RE, Scotland
| | - John G. McCarron
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow G4 0RE, Scotland
| | - Xinhua Shu
- Department of Life Sciences, Glasgow Caledonian University, Glasgow G4 0BA, Scotland
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Poteser M, Leitinger G, Pritz E, Platzer D, Frischauf I, Romanin C, Groschner K. Live-cell imaging of ER-PM contact architecture by a novel TIRFM approach reveals extension of junctions in response to store-operated Ca 2+-entry. Sci Rep 2016; 6:35656. [PMID: 27759093 PMCID: PMC5069484 DOI: 10.1038/srep35656] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Accepted: 09/29/2016] [Indexed: 01/16/2023] Open
Abstract
Nanometer-spaced appositions between endoplasmic reticulum and plasma membrane (ER-PM junctions) stabilized by membrane-joining protein complexes are critically involved in cellular Ca2+-handling and lipid trafficking. ER-PM junctional architecture and plasticity associated with inter-membrane communication are as yet barely understood. Here, we introduce a method to precisely characterize ER-PM junction morphology and dynamics with high temporal resolution and minimal disturbance of junctional intermembrane communication. We show that expression of soluble cytosolic fluorophores in combination with TIRFM enables to delineate ER and PM distance in the range of 10-150 nm. Live-cell imaging of sub-plasmalemmal structures in RBL-2H3 mast cells by this method, designated as fluorescence density mapping (FDM), revealed profound dynamics of ER-PM contact sites in response to store-depletion. We report the existence of a Ca2+-dependent process that expands the junctional ER to enlarge its contact surface with the PM, thereby promoting and stabilizing STIM1-Orai1 competent ER-PM junctions.
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Affiliation(s)
- Michael Poteser
- Institute of Biophysics, Medical University of Graz, Harrachgasse 21/4, 8010 Graz, Austria
| | - Gerd Leitinger
- Institute of Cell Biology, Histology and Embryology Research Unit “Electron Microscopic Techniques”, Medical University of Graz, Harrachgasse 21/7, 8010 Graz, Austria
| | - Elisabeth Pritz
- Institute of Cell Biology, Histology and Embryology Research Unit “Electron Microscopic Techniques”, Medical University of Graz, Harrachgasse 21/7, 8010 Graz, Austria
| | - Dieter Platzer
- Institute of Biophysics, Medical University of Graz, Harrachgasse 21/4, 8010 Graz, Austria
| | - Irene Frischauf
- Institute of Biophysics, Johannes Kepler University of Linz, Austria, Gruberstrasse 40, 4020 Linz, Austria
| | - Christoph Romanin
- Institute of Biophysics, Johannes Kepler University of Linz, Austria, Gruberstrasse 40, 4020 Linz, Austria
| | - Klaus Groschner
- Institute of Biophysics, Medical University of Graz, Harrachgasse 21/4, 8010 Graz, Austria
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