protein kinase A
cAMP response element
Springer Online Journal Archives 1860-2000
Chemistry and Pharmacology
Abstract Expression of the RIα regulatory subunit of protein kinase A type I is increased in human cancer cell lines, in primary tumors, in cells after transformation, and in cells upon stimulation of growth. Ala99 (the pseudophosphorylation site) of human RIα was replaced with Ser (RIα-p) for the structure-function analysis of RIα. MCF-7 hormone- dependent breast cancer cells were transfected with an expression vector for the wild-type RIα or mutant RIα-p. Overexpression of RIα-P resulted in suppression of protein kinase A type II, the isozyme of type I kinase, production of kinase exhibiting reduced cAMP activation, and inhibition of cell growth showing an increase in G0/G1 phase of the cell cycle and apoptosis. The wild-type RIα overexpression had no effect on protein kinase A isozyme distribution or cell growth. Overexpression of protein kinase A type II regulatory subunit, RIIβ, suppressed RIα and protein kinase A type I and inhibited cell growth. These results show that the growth of hormone-dependent breast cancer cells is dependent on the functional protein kinase A type I.
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