WNK1 phosphorylates synaptotagmin 2 and modulates its membrane binding.
WNK (with no lysine [K]) protein kinases were named for their unique active site organization. Mutations in WNK1 and WNK4 cause a familial form of hypertension by undefined mechanisms. Here, we report that WNK1 selectively binds to and phosphorylates synaptotagmin 2 ( Syt2) within its calcium binding C2 domains. Endogenous WNK1 and Syt2 coimmunoprecipitate and colocalize on a subset of secretory granules in INS-1 cells. Phosphorylation by WNK1 increases the amount of Ca2+ required for Syt2 binding to phospholipid vesicles; mutation of threonine 202, a WNK1 phosphorylation site, partially prevents this change. These findings suggest that phosphorylation of Syts by WNK1 can regulate Ca2+ sensing and the subsequent Ca2+-dependent interactions mediated by Syt C2 domains. These findings provide a biochemical mechanism that could lead to the retention or insertion of proteins in the plasma membrane. Interruption of this regulatory pathway may disturb membrane events that regulate ion balance.[1]References
- WNK1 phosphorylates synaptotagmin 2 and modulates its membrane binding. Lee, B.H., Min, X., Heise, C.J., Xu, B.E., Chen, S., Shu, H., Luby-Phelps, K., Goldsmith, E.J., Cobb, M.H. Mol. Cell (2004) [Pubmed]
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