Site-Specific Phosphorylatio of Synapsin I by Ca~2+/Calmodulin-Dependent Protein Kinase II in Pancreatic Βtc3 Cells: Synapsin Iis Not Associated With Insulin Secretory Granules

摘要

Increasing evidence supports a physiological role of Ca~2+/calmodulin-dependent protein kinase II (CaM Kinase II) in the secretio of insulin from the pancreatic β-cell, but the precise sites of actio are not known. A role of this enzyme in neuroexocytosis is implicated by its phosphorylation of a vesicle-associated protein, synapsin I. Because of emerging similarities to the neu- ron with respect to exocytotic mechanisms, the expres- sion and phosphorylation of synapsin I in the ?-cell have been studied. Synapsin I expression in clonal mouse β-cells (βTC3) and primary rat islet β-cells was initially confirmed by immunoblot analysis.