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Tetenborg S, Liss V, Breitsprecher L, Timonina K, Kotova A, Acevedo Harnecker AJ, Yuan C, Shihabeddin E, Ariakia F, Qin G, Chengzhi C, Dedek K, Zoidl G, Hensel M, O'Brien J. Intralumenal docking of connexin 36 channels in the ER isolates mistrafficked protein. J Biol Chem 2023; 299:105282. [PMID: 37742923 PMCID: PMC10637963 DOI: 10.1016/j.jbc.2023.105282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2023] [Revised: 08/30/2023] [Accepted: 09/05/2023] [Indexed: 09/26/2023] Open
Abstract
The intracellular domains of connexins are essential for the assembly of gap junctions. For connexin 36 (Cx36), the major neuronal connexin, it has been shown that a dysfunctional PDZ-binding motif interferes with electrical synapse formation. However, it is still unknown how this motif coordinates the transport of Cx36. In the present study, we characterize a phenotype of Cx36 mutants that lack a functional PDZ-binding motif using HEK293T cells as an expression system. We provide evidence that an intact PDZ-binding motif is critical for proper endoplasmic reticulum (ER) export of Cx36. Removing the PDZ-binding motif of Cx36 results in ER retention and the formation of multimembrane vesicles containing gap junction-like connexin aggregates. Using a combination of site-directed mutagenesis and electron micrographs, we reveal that these vesicles consist of Cx36 channels that docked prematurely in the ER. Our data suggest a model in which ER-retained Cx36 channels reshape the ER membrane into concentric whorls that are released into the cytoplasm.
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Affiliation(s)
| | - Viktoria Liss
- Department of Biology/Chemistry, iBiOs-Integrated Bioimaging Facility, CellNanOs - Center of Cellular Nanoanalytics, Osnabrück, Germany; Department of Microbiology, University of Osnabrück, Osnabrück, Germany
| | - Leonhard Breitsprecher
- Department of Biology/Chemistry, iBiOs-Integrated Bioimaging Facility, CellNanOs - Center of Cellular Nanoanalytics, Osnabrück, Germany; Department of Microbiology, University of Osnabrück, Osnabrück, Germany
| | - Ksenia Timonina
- Department of Biology, York University, Toronto, Ontario, Canada
| | - Anna Kotova
- Department of Biology, York University, Toronto, Ontario, Canada
| | | | - Chunxu Yuan
- Animal Navigation/Neurosensorics, Institute for Biology and Environmental Sciences, University of Oldenburg, Oldenburg, Germany
| | - Eyad Shihabeddin
- College of Optometry, University of Houston, Houston, Texas, USA; MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, Houston, Texas, USA
| | - Fatemeh Ariakia
- College of Optometry, University of Houston, Houston, Texas, USA
| | - Guoting Qin
- College of Optometry, University of Houston, Houston, Texas, USA
| | - Cai Chengzhi
- Department of Chemistry, University of Houston, Houston, Texas, USA
| | - Karin Dedek
- Animal Navigation/Neurosensorics, Institute for Biology and Environmental Sciences, University of Oldenburg, Oldenburg, Germany; Research Center Neurosensory Science, University of Oldenburg, Oldenburg, Germany
| | - Georg Zoidl
- Department of Microbiology, University of Osnabrück, Osnabrück, Germany
| | - Michael Hensel
- Department of Biology/Chemistry, iBiOs-Integrated Bioimaging Facility, CellNanOs - Center of Cellular Nanoanalytics, Osnabrück, Germany; Department of Microbiology, University of Osnabrück, Osnabrück, Germany
| | - John O'Brien
- College of Optometry, University of Houston, Houston, Texas, USA.
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