Tyrosine kinases act directly on the α1 subunit to modulate Cav2.2 calcium channels

Voltage-operated calcium channels are modulated by tyrosine kinases in different cell types. In this study, I(Ba) was measured by the whole cell voltage-clamp technique in single COS-7 cells overexpressing the Ca(v)2.2 calcium channels encoding N-type currents. Bath application of genistein, a nonselective PTK inhibitor (50-300 muM), concentration-dependently inhibited calcium channel currents, whereas the inactive structural analogue, daidzein, was without effect over the same concentration range. Similarly, PP1, a src family-selective tyrosine kinase inhibitor, inhibited I(Bn) in a concentration-dependent manner (500 nM-5 muM) over a range of test potentials. Expression of the Ca(v)2.2alpha1 (alpha(1B)) subunit alone gave rise to functional channels, and genistein (100 muM) also inhibited currents elicited by the a,g subunit alone. These results indicate that tyrosine kinase inhibitors are likely to inhibit Ca(v)2.2 calcium channels via an action on the pore-forming a, subunit and suggest that an endogenous member of the Src family may play a physiological role in modulating these channels. (C) 2002 Elsevier Science (USA).