Activation of Calcium Channels by cAMP in STC-1 Cells Is Dependent upon Ca²⁺ Calmodulin-Dependent Protein Kinase II

Author： Basavappa S. Mangel A.W. Scott L. Liddle R.A.

Publisher： Elsevier

ISSN： 0006-291X

Source： Biochemical and Biophysical Research Communications, Vol.254, Iss.3, 1999-01, pp. : 699-702

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Abstract

Activation of L-type calcium channels in the neuroendocrine, cholecytstokinin-secreting cell line, STC-1, is vital for secretion of CCK. In the present study, the regulation of L-type Ca²⁺ channels by cAMP and Ca²⁺ calmodulin dependent protein kinase II (CaM-KII) in STC-1 cells was investigated. Exposure to 3-isobutyl-1-methylxanthine (IBMX) increased intracellular cAMP levels, whole cell Ca²⁺ currents and activated Ca²⁺ channels in cell-attached membrane patches. Furthermore, in Fura-2AM loaded cells, cytosolic Ca²⁺ levels increased upon exposure to IBMX. By contrast, pretreatment of cells with the CaM-KII inhibitor KN-62, prevented IBMX activation of Ca²⁺ channels in cell-attached patches or increases in cytosolic Ca²⁺ levels. Inclusion of the synthetic peptide fragment 290-309 of CaM-KII, a CaM-KII antagonist, in the pipette solution, blocked the activation of whole cell Ca²⁺ currents upon addition of IBMX. These results indicate a unique mechanism of L-type Ca²⁺ channel activation involving two phosphorylation events.