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J Gen Physiol. 2018 May 7;150(5):683-696. doi: 10.1085/jgp.201812064. Epub 2018 Apr 25.

Dimerization of the voltage-sensing phosphatase controls its voltage-sensing and catalytic activity.

Author information

1
Department of Cell Biology and Neuroscience, Montana State University, Bozeman, MT.
2
Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Medicale, iBV, Université Côte d'Azur, Valbonne, France.
3
Laboratory of Excellence, Ion Channel Science and Therapeutics, Nice, France.
4
Department of Cell Biology and Neuroscience, Montana State University, Bozeman, MT skohout@montana.edu.

Abstract

Multimerization is a key characteristic of most voltage-sensing proteins. The main exception was thought to be the Ciona intestinalis voltage-sensing phosphatase (Ci-VSP). In this study, we show that multimerization is also critical for Ci-VSP function. Using coimmunoprecipitation and single-molecule pull-down, we find that Ci-VSP stoichiometry is flexible. It exists as both monomers and dimers, with dimers favored at higher concentrations. We show strong dimerization via the voltage-sensing domain (VSD) and weak dimerization via the phosphatase domain. Using voltage-clamp fluorometry, we also find that VSDs cooperate to lower the voltage dependence of activation, thus favoring the activation of Ci-VSP. Finally, using activity assays, we find that dimerization alters Ci-VSP substrate specificity such that only dimeric Ci-VSP is able to dephosphorylate the 3-phosphate from PI(3,4,5)P3 or PI(3,4)P2 Our results indicate that dimerization plays a significant role in Ci-VSP function.

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