Regulation of Ca-sensitive inactivation of a 1-type Ca2+ channel by specific domains of beta subunits

Ca2+ channel auxiliary beta subunits have been shown to modulate voltage-de pendent inactivation of various types of Ca2+ channels. The beta(1) and bet a(2) subunits, that are differentially expressed with the L-type alpha(1) C a2+ channel subunit in heart, muscle and brain, can specifically modulate t he Ca2+-dependent inactivation kinetics. Their expression in Xenopus oocyte s with the alpha(1C) subunit leads, in both cases, to biphasic Ca2+ current decays, the second phase being markedly slowed by expression of the beta(2 ) subunit, Using a series of beta subunit deletion mutants and chimeric con structs of beta(1) and beta(2) subunits, we show that the inhibitory site l ocated on the amino-terminal region of the beta(2a), subunit is the major e lement of this regulation. These results thus suggest that different splice variants of the beta(2) subunit can modulate, in a specific way, the Ca2entry through L-type Ca2+ channels in different brain or heart regions. (C) 1999 Federation of European Biochemical Societies.