Figure 1.

Whole-cell current properties of Ca_V1.2 channels modulated by Ca_Vβ_1a and Ca_Vβ_2b subunits and their mixtures. (A) Micrographs showing HEK293α_1C cells after transfection with vectors encoding Ca_Vβ and Ca_Vα₂δ1 subunits. (Red and green fluorescences) DsRed2 and EGF proteins reporting expression of Ca_Vβ_1a and Ca_Vβ_2b subunits, respectively, in the cells. (B) Representative whole-cell Ba²⁺ current traces. Ca_Vβ subunits used for transfections are indicated above the traces. (C–E) Properties of Ca_V1.2 channels in β⁻ cells (open circles, n = 5), and in cells cotransfected with Ca_Vβ_1a (up-pointing triangles, n = 9), Ca_Vβ_1aCa_Vβ_2b mixture (2:1) (solid circles, n = 8), Ca_Vβ_1aCa_Vβ_2b mixture (1:1) (solid diamonds, n = 6), and Ca_Vβ_2b (down-pointing triangles, n = 6). Symbols with error bars represent mean ± SE. Curves show fits of the average data. (C) I/V curves were obtained by depolarizing from –100 mV holding potential to test voltages between –40 and +60 mV. The data were fitted with a Boltzmann-Ohm function. (D) Activation curves were obtained from fitting of normalized tail currents with a Boltzmann function. (E) To study the steady-state inactivation, peak current amplitudes at +10 mV were measured immediately after a 5-s conditioning potential. The data were fitted using the Boltzmann equation.