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WNK1 phosphorylates synaptotagmin 2 and modulates its membrane binding
Byung-Hoon Lee1, Xiaoshan Min, Charles J Heise
1Department of Pharmacology, The University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA.
Molecular Cell
|September 8, 2004
Summary
WNK1 protein kinase phosphorylates synaptotagmin 2, altering its calcium binding. This discovery reveals a new mechanism for regulating membrane protein insertion and ion balance, potentially impacting hypertension.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- WNK (with no lysine [K]) protein kinases are implicated in familial hypertension.
- The precise mechanisms by which WNK1 and WNK4 mutations cause hypertension remain undefined.
Purpose of the Study:
- To elucidate the molecular mechanism by which WNK kinases may contribute to hypertension.
- To investigate the interaction between WNK1 and its potential substrates.
Main Methods:
- Co-immunoprecipitation assays to detect WNK1 and synaptotagmin 2 interaction.
- Cellular colocalization studies using INS-1 cells.
- In vitro phosphorylation assays to determine the effect of WNK1 on synaptotagmin 2 function.
Main Results:
- WNK1 selectively binds to and phosphorylates synaptotagmin 2 (Syt2) in its calcium-binding C2 domains.
- Endogenous WNK1 and Syt2 were found to co-immunoprecipitate and colocalize on secretory granules.
- WNK1-mediated phosphorylation of Syt2 increases the calcium concentration required for its binding to phospholipid vesicles.
Conclusions:
- WNK1 phosphorylation of Syt2 regulates calcium sensing and subsequent Ca2+-dependent interactions.
- This regulatory pathway provides a biochemical mechanism for controlling protein retention/insertion in the plasma membrane.
- Disruption of this WNK1-Syt2 pathway may affect membrane events critical for maintaining ion balance and could be linked to hypertension.