Figure 1
SmCa v β modulates Ca v 2.3 currents in HEK cells. A. Representative Ca2+ currents generated by voltage steps to -5, +15, +35 and +55 mV from a holding potential of -80 mV in HEK cells expressing Cav2.3 alone and in combination with SmCavβ or Cavβ2a. B. Current-voltage relationships from HEK cells expressing Cav2.3 alone (filled circles) and in combination with SmCavβ (open circles) or Cavβ2a (filled triangles). Peak currents generated by voltage steps from -20 mV to +75 mV in 5 mV steps from a holding potential of -80 mV were measured. Data points represent mean ± s.e.m. N = 5–15. C. Two-variable plot showing the relationships between inactivation time constants and percentages of contribution to total inactivation for Cav2.3 alone (filled circles) and in combination with SmCavβ (open circles). Data points represent mean ± s.e.m. N = 7–9. Slow time constants for the kinetic of recovery are grouped (dotted lines). Fast time constants of recovery from inactivation kinetics are also grouped (dotted lines). D. Voltage-dependence of inactivation (steady-state inactivation) for Cav2.3 alone (filled circles) and in combination with SmCavβ (open circles) or Cavβ2a (filled triangles). Lines represent fits to the Boltzmann function (see Materials and Methods); V50 and slope values are shown in Table 1. Data points represent mean ± s.e.m. N = 3–6. E. Recovery from inactivation from -100 mV for Cav2.3 channels alone (filled circles) or in the presence of SmCavβ (open circles), using Ba2+ as the charge carrier. Solid curves represent single exponential fits to the data. Values are means ± s.e.m. N = 3.