Protein Kinase CK2 Controls Ca(V)2.1-Dependent Calcium Currents and Insulin Release in Pancreatic β-cells

The regulation of insulin biosynthesis and secretion in pancreatic β-cells is essential for glucose homeostasis in humans. Previous findings point to the highly conserved, ubiquitously expressed serine/threonine kinase CK2 as having a negative regulatory impact on this regulation. In the cell culture model of rat pancreatic β-cells INS-1, insulin secretion is enhanced after CK2 inhibition. This enhancement is preceded by a rise in the cytosolic Ca(2+) concentration. Here, we identified the serine residues S(2362) and S(2364) of the voltage-dependent calcium channel Ca(V)2.1 as targets of CK2 phosphorylation. Furthermore, co-immunoprecipitation experiments revealed that Ca(V)2.1 binds to CK2 in vitro and in vivo. Ca(V)2.1 knockdown experiments showed that the increase in the intracellular Ca(2+) concentration, followed by an enhanced insulin secretion upon CK2 inhibition, is due to a Ca(2+) influx through Ca(V)2.1 channels. In summary, our results point to a modulating role of CK2 in the Ca(V)2.1-mediated exocytosis of insulin.