Table 7.
Biophysical properties of CaV1.2 macroscopic whole‐cell patch currents for WT versus IQ motif mutants
| Analysis | I‐V | G‐V | Charge movement | ITail/Qon | ||||
|---|---|---|---|---|---|---|---|---|
| Parameter | V1/2act. (mV) | kact. | Erev. (mV) | V1/2act. (mV) | klow | khigh | Qon (fC/pF) | Slope |
| WT (a) | −18.5 ± 0.5 | −4.2 ± 0.4 (10) | 51.3 ± 1.3 | −6.5.0 ± 0.4 | 7.0 ± 0.3 (16) | −8.5 ± 27.4 | 3.8 ± 0.9 (18) | 3.9 ± 1.5 (16) |
| K1647A (b) | −19.9 ± 0.9 | −5.9 ± 0.6 (11) | 55.2 ± 2.0 | −8.5.0 ± 0.9 | 8.5 ± 0.8 (15) | 9.0 ± 10.5 | 1.3 ± 0.3* (15) | 0.26 ± 1.5 (15) |
| Y1649A (c) | −19.9 ± 0.6 | −4.0 ± 0.5 (10) | 49.2 ± 1.5 | −6.3.0 ± 0.7 | 7.5 ± 0.8 (16) | 28.7 ± 6.9 | 0.98 ± 0.3** (13) | 0.19 ± 1.0 (12) |
| I1654A (d) | −12.6 ± 1.0**** | −5.4 ± 0.7 (5) | 48.2 ± 2.6 | −2.5 ± 0.9** | 7.5 ± 0.9 (13) | 38.5 ± 11.5 | 0.87 ± 0.3** (13) | 1.3 ± 0.6 (12) |
| F1658A (e) | −26.5 ± 1.1** | −4.5 ± 0.9 (6) | 58.6 ± 4.1 | −10.6 ± 1.4** | 5.3 ± 1.6 (11) | 20.2 ± 3.9 | 2.8 ± 0.6 (13) | 3.1 ± 1.4 (12) |
| K1662E (f) | −20.2 ± 0.4 | −4.2 ± 0.3 (12) | 50.1 ± 1.2 | −6.1.0 ± 0.7 | 7.9 ± 0.8 (21) | 49.2 ± 19.4 | 3.5 ± 1.1 (17) | 2.2 ± 1.0 (14) |
| ANOVA/t‐test | a‐d† | a‐d† | a‐b† | |||||
| a‐c† | ||||||||
| a‐e† | NS | NS | a‐e† | NS | NS | a‐d† | ||
HEK293 cells were transiently transfected with WT CaV1.2 (α11.2, α2‐δ1, and β2a). Whole‐cell patch recording was performed in 20 mM Ba2+ (see Fig 7). To obtain current–voltage relationships (I‐V), currents were recorded upon depolarization from a holding potential of −80 mV to increasingly more positive potentials (see Fig 7A for details). The voltage for half maximal activation (V1/2act), activation constant (kact), and reversal potential (Erev) was determined. To obtain conductance–voltage relationships (G‐V), tail currents (ITail) were recorded upon repolarization to −50 mV following depolarization from a holding potential of −80 mV to increasingly more positive potentials (see Fig 7A for details). The activation kinetics for G‐V were best described by double exponential fits, and the rate constants k high and k low were determined accordingly. Total charge movement (Qon) and the ratio of ITail/Qon were determined as in Fig 7. Statistical significance was determined by pairwise multiple testing WT (a) against K1647A (b), Y1649A (c), I1654A (d), F1658A (e), and K1662E (f) by a one‐way ANOVA with a Bonferroni† post hoc test. Given are mean values ± SEM (*P < 0.05, **P < 0.01, ****P < 0.0001).