Lm. Matovcik et al., CELLULAR-LOCALIZATION OF CALMODULIN-DEPENDENT PROTEIN-KINASE-I AND PROTEIN-KINASE-II TO A-CELLS AND D-CELLS OF THE ENDOCRINE PANCREAS, The Journal of histochemistry and cytochemistry, 46(4), 1998, pp. 519-526
Ca2+/calmodulin-dependent protein kinases I and II, initially identifi
ed in brain on the basis of their ability to phosphorylate synapsin I,
have been implicated in the regulation of Ca2+-dependent synaptic neu
rosecretion. Specific recombinant and synthetic peptide antibodies wer
e used to examine the distribution of CaM kinases I and II in the rat
pancreas and other tissues. The CaM kinase I antibodies detected a dou
blet of cytosolic proteins of similar to 38 and similar to 42 kD by im
munoblot. CaM kinase I was observed in glucagon-containing A-cells at
the periphery of the islet of Langerhans but had little or no overlap
with pancreatic polypeptide or somatostatin cells. In contrast, CaM ki
nase II was localized to somatostatin-containing D-cells. CaM kinase I
co-localized with glucagon secretory granules. CaM kinase II was not
associated with the somatostatin granule but rather was enriched in ar
eas of the cells that contained relatively little somatostatin. Becaus
e glucagon secretion is Ca2+-dependent, it is attractive to speculate
that CaM kinase I may play a regulatory role in glucagon secretion. Gl
ucagon and somatostatin cells both utilize intracellular Ca2+ for sign
aling. Therefore, specific CaM kinases may act as effecters of Ca2+ in
these different cell types.