Table 2. CaV1.2 Inactivation Parameters and GV Relationshipa.
| ti300 (%) | A1 (%) | τ1 (ms) | A2 (%) | τ2 (ms) | Imax | V1/2 | N | ||
|---|---|---|---|---|---|---|---|---|---|
| CaV1.2:CaVβ2a | 68.4 ± 1.1 | 49.4 ± 1.9 | 25.4 ± 1.2 | 21.3 ± 1.2 | 159.6 ± 8.4 | –0.411 ± 0.054 | 8.1 ± 1.2 | 25 | |
| CaV1.2-Y437A:CaVβ2a | 66.0 ± 3.2 | 51.6 ± 3.7 | 31.2 ± 4.6 | 22.5 ± 3.9 | 177.3 ± 10.9 | –0.816 ± 0.237 | 7.5 ± 1.4 | 6 | |
| CaV1.2:CaVβ3 | 75.9 ± 1.1 | 70.3 ± 0.9 | 59.8 ± 2.5 | –0.964 ± 0.008 | 5.5 ± 1.4 | 20 | |||
| 59.9 ± 1.9 | 33.9 ± 3.0 | 25.4 ± 1.6 | 312.0 ± 47.7 | ||||||
| CaV1.2, no CaVβ | 47.9 ± 1.2 | 26.8 ± 3.6 | 75.5 ± 10.3 | 48.4 ± 4.8 | 348.3 ± 41.4 | –0.245 ± 0.028 | 18.1 ± 1.0 | 14 | |
| CaV1.2-Y437A:CaVβ2a | water 5 min | 67.2 ± 1.9 | 51.9 ± 2.2 | 28.0 ± 1.5 | 19.7 ± 1.2 | 170.5 ± 6.3 | –0.722 ± 0.092 | 7.8 ± 1.3 | 5 |
| water 30 min | 59.8 ± 2.6 | 42.6 ± 2.6 | 31.6 ± 2.9 | 23.7 ± 1.6 | 200.5 ± 13.8 | –0.430 ± 0.075 | 11.1 ± 1.2 | 5 | |
| HotA, 5 min | 68.8 ± 1.0 | 54.0 ± 1.2 | 33.2 ± 1.4 | 20.0 ± 1.3 | 212.5 ± 16.4 | –1.001 ± 0.153 | 4.7 ± 1.4 | 18 | |
| HotA, 30 min | 63.7 ± 1.3 | 47.2 ± 1.2 | 34.5 ± 1.7 | 22.0 ± 1.0 | 197.9 ± 10.1 | –0.578 ± 0.064 | 7.1 ± 1.1 | 18 | |
| AID-CAP, 5 min | 65.5 ± 1.3 | 52.7 ± 1.3 | 32.9 ± 1.7 | 18.8 ± 1.1 | 212.6 ± 18.6 | –1.016 ± 0.122 | 5.4 ± 1.4 | 16 | |
| AID-CAP, 30 min | 43.1 ± 3.7 | 24.8 ± 3.2 | 52.8 ± 8.2 | 38.2 ± 3.0 | 469.8 ± 160.1 | –0.156 ± 0.022 | 16.9 ± 1.0 | 15 | |
| AID, 5 min | 64.9 ± 1.9 | 48.5 ± 1.8 | 35.0 ± 1.5 | 24.1 ± 1.6 | 251.5 ± 16.1 | –0.883 ± 0.111 | 2.9 ± 1.7 | 10 | |
| AID, 30 min | 44.8 ± 2.1 | 24.5 ± 3.0 | 53.3 ± 14.4 | 31.0 ± 1.9 | 304.0 ± 50.9 | –0.242 ± 0.021 | 15.1 ± 2.0 | 10 | |
| CaV1.2:CaVβ2a | water 5 min | 60.8 ± 1.0 | 40.0 ± 1.1 | 34.6 ± 3.9 | 27.1 ± 0.8 | 222.8 ± 31.6 | –1.344 ± 0.248 | 9.1 ± 1.8 | 5 |
| water 30 min | 58.1 ± 1.4 | 38.3 ± 2.5 | 37.3 ± 3.0 | 27.1 ± 2.0 | 227.3 ± 12.1 | –0.785 ± 0.074 | 11.6 ± 0.7 | 5 | |
| HotA, 5 min | 66.8 ± 0.3 | 47.5 ± 1.0 | 28.4 ± 0.7 | 24.6 ± 1.0 | 185.7 ± 2.1 | –0.734 ± 0.110 | 10.5 ± 1.5 | 3 | |
| HotA, 30 min | 62.1 ± 0.2 | 44.4 ± 0.8 | 33.5 ± 2.3 | 24.7 ± 0.6 | 209.5 ± 13.2 | –0.531 ± 0.098 | 9.0 ± 0.5 | 3 | |
| AID-CAP 400 μM, 5 min | 63.7 ± 1.9 | 41.6 ± 2.5 | 33.0 ± 2.3 | 28.9 ± 1.8 | 215.8 ± 13.2 | –0.966 ± 0.154 | 9.2 ± 1.5 | 8 | |
| AID-CAP 400 μM, 30 min | 57.1 ± 1.6 | 33.1 ± 2.0 | 35.0 ± 1.7 | 28.6 ± 2.0 | 209.7 ± 9.3 | –0.555 ± 0.132 | 13.0 ± 1.7 | 8 | |
| AID-CAP 2.8 mM, 5 min | 64.6 ± 1.3 | 52.4 ± 3.1 | 29.2 ± 3.3 | 19.3 ± 2.2 | 172.5 ± 23.4 | –0.984 ± 0.142 | 7.2 ± 0.7 | 5 | |
| AID-CAP 2.8 mM, 30 min | 62.4 ± 2.6 | 48.1 ± 5.5 | 30.7 ± 6.0 | 27.3 ± 1.3 | 172.2 ± 25.9 | –0.465 ± 0.079 | 10.4 ± 0.7 | 5 | |
| CaV1.2:CaVβ3 | HotA, 5 min | 79.2 ± 2.2 | 79.7 ± 2.3 | 63.0 ± 2.4 | –0.932 ± 0.041 | 6.7 ± 2.9 | 5 | ||
| 61.0 ± 2.4 | 38.5 ± 1.5 | 27.9 ± 0.8 | 256.8 ± 10.8 | 5 | |||||
| HotA, 30 min | 77.0 ± 2.9 | 78.0 ± 2.7 | 71.4 ± 4.6 | –0.577 ± 0.069 | 8.6 ± 3.3 | 5 | |||
| 56.5 ± 2.0 | 42.9 ± 4.4 | 30.0 ± 1.4 | 241.1 ± 14.6 | 5 | |||||
| AID-CAP, 5 min | 73.2 ± 1.4 | 75.9 ± 1.2 | 76.2 ± 4.2 | –0.889 ± 0.135 | 6.3 ± 1.6 | 6 | |||
| 57.8 ± 1.2 | 48.0 ± 3.7 | 42.0 ± 8.3 | 639.1 ± 238.3 | 6 | |||||
| AID-CAP, 30 min | 48.3 ± 4.1 | 66.3 ± 5.0 | 188.7 ± 30.2 | –0.081 ± 0.023 | 20.5 ± 2.8 | 6 | |||
| ND | ND | ND | ND | ||||||
| AID, 5 min | 73.4 ± 2.0 | 76.9 ± 3.1 | 62.6 ± 7.6 | –0.860 ± 0.096 | 10.4 ± 2.2 | 7 | |||
| 54.0 ± 2.7 | 40.0 ± 5.2 | 34.1 ± 1.4 | 354.4 ± 119.2 | 7 | |||||
| AID, 30 min | 49.8 ± 1.9 | 65.0 ± 4.0 | 118.2 ± 11.0 | –0.116 ± 0.010 | 21.0 ± 2.0 | 7 | |||
| ND | ND | ND | ND |
a
Data are expressed as mean values ± SEM; τ values were determined at a holding potential of +20 mV (see Materials and Methods); ti300 denotes percent inactivation at 300 ms. Imax is the maximal current amplitude. V1/2 values for CaV1.2 and mutants were determined with calcium as the charge carrier. Data were fit using the equation I = Gmax(Vm – Vrev)/(1 + exp[(V1/2 – Vm)/Ka]), where I is the measured peak current at each Vm, Gmax is the maximal macroscopic conductance, Vm is the test potential, Vrev is the reversal potential, V1/2 is the midpoint of activation, and Ka is the slope factor.29 ND, value not determined. Italic lines highlight double exponential fit values for CaVβ3 experiments.