Regulation of Ca‐sensitive inactivation of a l‐type Ca2+ channel by specific domains of β subunits

Abstract
Ca2+ channel auxiliary β subunits have been shown to modulate voltage‐dependent inactivation of various types of Ca2+ channels. The β1 and β2 subunits, that are differentially expressed with the L‐type α1 Ca2+ channel subunit in heart, muscle and brain, can specifically modulate the Ca2+‐dependent inactivation kinetics. Their expression in Xenopus oocytes with the α1C subunit leads, in both cases, to biphasic Ca2+ current decays, the second phase being markedly slowed by expression of the β2 subunit. Using a series of β subunit deletion mutants and chimeric constructs of β1 and β2 subunits, we show that the inhibitory site located on the amino‐terminal region of the β2a subunit is the major element of this regulation. These results thus suggest that different splice variants of the β2 subunit can modulate, in a specific way, the Ca2+ entry through L‐type Ca2+ channels in different brain or heart regions.