Single-channel activity of L-type Ca2+ channels reconstituted with the β2c subunit cloned from the rat heart

Abstract We recently cloned the β 2c subunit of the L-type Ca 2+ channel as a functional type of β subunit from the rat heart. In order to clarify the contribution of the β 2c subunit to native Ca 2+ channel function, we investigated the single-channel properties of Ca 2+ channels reconstituted with β 2a or β 2c subunits and compared them with the properties of native channels. In contrast to the Ca 2+ channel with β 2a subunit, long-lasting closings were dominant in the Ca 2+ channel with β 2c subunit and the native channel. The ensemble-averaged current of the cells with β 2c subunits was comparable to that of the native cardiomyocytes. Many high P o sweeps (mode 2) were observed in the cells with β 2a subunits, while only a few high P o sweeps were observed in the cells with β 2c subunits and the native cells. These findings suggest that the β 2c subunit is one of the functional β subunits in the rat heart.