The β1‐subunit is essential for modulation by protein kinase C of an human and a non‐human L‐type Ca2+ channel

We have investigated in Xenopus oocytes the effects of phorbol ester-induced protein kinase C (PKC) stimulation on dihydropyridine (DHP)-insensitive and -sensitive Ca2+ channels. DHP-insensitive Ba2+ currents (IBa) were recorded from endogenous channels in non-injected oocytes and in oocytes injected with cRNAs encoding the auxiliary rabbit alpha 2/delta and beta 1 Ca2+ channel subunits. A human alpha 1C cRNA, injected alone or in combination with cRNAs of the auxiliary subunits, was used for studying DHP-sensitive IBa. We found that DHP-insensitive IBa was increased by 4 beta-phorbol 12-myristate 13-acetate (PMA), while DHP-sensitive IBa was decreased. In both cases, the effects depended only on the co-expression of the beta 1 subunit.