Abstract
It is well established that the auxiliary Cavβ subunit regulates calcium channel density in the plasma membrane, but the cellular mechanism by which this occurs has remained unclear. We found that the Cavβ subunit increased membrane expression of Cav1.2 channels by preventing the entry of the channels into the endoplasmic reticulum–associated protein degradation (ERAD) complex. Without Cavβ, Cav1.2 channels underwent robust ubiquitination by the RFP2 ubiquitin ligase and interacted with the ERAD complex proteins derlin-1 and p97, culminating in targeting of the channels to the proteasome for degradation. On treatment with the proteasomal inhibitor MG132, Cavβ-free channels were rescued from degradation and trafficked to the plasma membrane. The coexpression of Cavβ interfered with ubiquitination and targeting of the channel to the ERAD complex, thereby facilitating export from the endoplasmic reticulum and promoting expression on the cell surface. Thus, Cavββ regulates the ubiquitination and stability of the calcium channel complex.
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Acknowledgements
We thank J. Striessnig, S. Ferguson, J. Stutts, B. Schwappach, E. Bourinet and T. Snutch for cDNA constructs, and E. Stanley for help with the ICQ colocalization analysis. This work was supported by operating grants to G.W.Z. from the Heart and Stroke Foundation of Alberta, the Northwest Territories and Nunavut, and the Canadian Institutes for Health Research. G.W.Z. is a Scientist of the Alberta Heritage Foundation for Medical Research (AHFMR) and a Canada Research Chair in Molecular Neurobiology. H.Y. is supported by an AFHMR fellowship and B.S. is supported by an AHFMR studentship.
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C.A., A.G.-C. and G.W.Z. designed the study and wrote the manuscript. G.W.Z. supervised the study. C.A., A.G.-C., B.S., H.Y. and L.C. performed experiments and data analysis. J.W. and H.W.T. contributed to molecular biology.
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Altier, C., Garcia-Caballero, A., Simms, B. et al. The Cavβ subunit prevents RFP2-mediated ubiquitination and proteasomal degradation of L-type channels. Nat Neurosci 14, 173–180 (2011). https://doi.org/10.1038/nn.2712
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DOI: https://doi.org/10.1038/nn.2712
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