Abstract
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 Ca 2+-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.
| Original language | English |
|---|---|
| Pages (from-to) | 741-751 |
| Number of pages | 11 |
| Journal | Molecular Cell |
| Volume | 15 |
| Issue number | 5 |
| DOIs | |
| State | Published - 10 Sep 2004 |
Bibliographical note
Funding Information:We thank Joe Albanesi, Barbara Barylko, Tom Südhof, Jose Rizo-Rey, Elliott Ross, Paul Sternweis, Cai Li, and members of the Cobb laboratory (UT Southwestern) for comments about the data and manuscript, Malavika Raman for suggestions about data presentation, Tom Südhof for cDNAs encoding Syt isoforms, Mark Henkemeyer for the brain cDNA library, Marc Mumby for suggestions about mass spectrometry, Svetlana Earnest and Steve Stippec for technical assistance, and Dionne Ware for administrative assistance. This work was supported by grants from the National Institutes of Health (GM53032 to M.H.C.) and the Welch Foundation (I1243 to M.H.C. and I1128 to E.J.G.). This work partially fulfills the requirements for the Ph.D. degree.