Protein kinase C activation inhibits Cav1.3 calcium channel at NH2-terminal serine 81 phosphorylation site.

The Cav1.3 (α1D) variant of L-type Ca2+ channels plays a vital role in the function of neuroendocrine and cardiovascular systems. In this article, we report on the molecular and functional basis of α1D Ca2+ channel modulation by protein kinase C (PKC). Specifically, we show that the serine 81 (S81) phosphorylation site at the NH2-terminal region plays a critical role in α1D Ca2+ channel modulation by PKC. The introduction of a negatively charged residue at position 81, by converting serine to aspartate, mimicked the PKC phosphorylation effect on α1D Ca2+ channel. The modulation of α1D Ca2+ channel by PKC was prevented by dialyzing cells with a 35-amino acid peptide mimicking the α1D NH2-terminal region comprising S81. In addition, the data revealed that only βII- and ePKC isozymes are implicated in this regulation. These novel findings have significant implications in the pathophysiology of α1D Ca2+ channel and in the development of PKC isozyme-targeted therapeutics.