PKA-DEPENDENT REGULATION OF MKV1.1, A MOUSE SHAKER-LIKE POTASSIUM CHANNEL GENE, WHEN STABLY EXPRESSED IN CHO CELLS

Potassium (K) channels are important regulators of cellular physiology and can themselves be modulated by phosphorylation. We have investiga ted the potential protein kinase A (PKA) regulation of mKv 1. 1, a mou se Shaker-like K channel gene, when it is expressed in stably transfec ted Chinese hamster ovary (CHO) cell lines. Whole-cell patch-clamp rec ords show that expression of mKv1.1 gives rise to a rapidly activating , sustained K+ current, referred to classically as a delayed rectifier -type current. In order to study the effects of PKA, we compared cell lines transfected with mKv1.1 alone with lines cotransfected with both mKv1. 1 and a plasmid encoding a dominant negative mutation in the re gulatory subunit of PKA. These mutant regulatory subunits bind to endo genous catalytic subunits of PKA but do not respond to cAMP, thereby c ausing a chronic reduction in the basal PKA activity in these cells. W e found that mKv1.1 current kinetics are unaltered but current density is 3.4-fold higher in the cell lines expressing mutant regulatory sub unit than in lines expressing only mKv1. 1. RNase protection assays in dicate that levels of the specific RNA for mKv1. 1 are increased almos t twofold in the lines expressing mutant regulatory subunit over the l ines expressing mKv1. 1 only. Further, the levels of mKv1. 1 protein, assayed using an mKv1. 1 channel-specific antibody, are increased by a lmost a factor of 3 between the two types of cell lines. These results suggest that PKA can regulate mKv1.l channel expression by changing s teady-state levels of RNA and by other posttranscriptional mechanisms.