Protein kinase C isozyme-specific potentiation of expressed Ca sub(v) 2.3 currents by acetyl- beta -methylcholine and phorbol-12-myristate, 13-acetate

Protein kinase C (PKC) is implicated in the potentiation of Ca sub(v) 2.3 currents by acetyl- beta -methylcholine (MCh), a muscarinic M sub(1) receptor agonist or phorbol-12-myristate, 13-acetate (PMA). The PKC isozymes responsible for the action of MCh and PMA were investigated using translocation as a measure of activation and with isozyme-selective antagonists and siRNA. Ca sub(v) channels were expressed with alpha sub(1) 2.3, beta sub(1)b and alpha sub(2) delta subunits and muscarinic M sub(1) receptors in the Xenopus oocytes and the expressed currents (I sub(B) sub(a)) were studied using Ba super(2) super(+) as the charge carrier. Translocation of PKC isozymes to the membrane studied by Western blot revealed that all eleven known PKC isozymes are present in the Xenopus oocytes. Exposure of the oocytes to MCh led to the translocation of PKC alpha whereas PMA activated PKC beta II and approximately equal to isozymes. The action of MCh was inhibited by Go 6976, an inhibitor of cPKC isozymes or PKC alpha siRNA. PMA-induced potentiation of Ca sub(v) 2.3 currents was inhibited by CG533 53, a PKC beta II antagonist, beta IIV5.3, a peptide translocation inhibitor of PKC beta II or PKC beta II siRNA. Similarly, approximately equal to V1.2, a peptide translocation inhibitor of PKC approximately equal to or PKC approximately equal to siRNA inhibited PMA action. The inhibitors of PKC increased the basal I sub(B) sub(a) slightly. It is possible that some PKC isozymes have negative control over the I sub(B) sub(a). Our results implicate PKC alpha in the potentiation of Ca sub(v) 2.3 currents by MCh and PKC beta II and approximately equal to in the potentiation of Ca sub(v) 2.3 currents by PMA.