Differential PKA-dependent regulation of CaV1.2Δ1800 channels via AKAP15 and AKAP79. (A) Representative IBa through CaV1.2Δ1800 and CaV1.2Δ1800 + DCT channels coexpressed with cDNA ratios of either 0.003:1 AKAP15 or 0.01:1 AKAP79 in tsA-201 cells in the absence or presence of 5 µM forskolin (Fsk) elicited by test pulses ranging from −60 to 10 mV (top) or test pulses to Vrev (bottom) from a holding potential of −80 mV. (B) Mean current-voltage relationships for CaV1.2Δ1800 and CaV1.2Δ1800 + DCT channels with 0.003:1 AKAP15 or 0.01:1 AKAP79 and 5 µM forskolin. (C) Coupling ratio (nA/pC) for CaV1.2Δ1800 and CaV1.2Δ1800 + DCT channels with AKAP15 or AKAP79 at the indicated ratios, without and with 5 µM forskolin. Dashed line indicates mean current for unstimulated CaV1.2Δ1800 + DCT. n values and ±SEM are indicated. **, P < 0.01 versus control. Significance was determined by ANOVA followed by Dunnett’s post-test. (D) Mean current-voltage relationships for CaV1.2Δ1800 and CaV1.2Δ1800 + DCT channels with 0.003:1 AKAP15 or 0.01:1 AKAP79 and 5 µM forskolin in the presence of PKA expressed at 1:1 cDNA ratio. (B and D) Error bars are SEM. (E) Coupling ratio (nA/pC) for CaV1.2Δ1800 and CaV1.2Δ1800 + DCT channels with AKAP15 or AKAP79, without and with 5 µM forskolin, in the presence of PKA expressed at 1:1 cDNA ratio. Dashed line indicates mean coupling ratio for unstimulated CaV1.2Δ1800 + DCT. n values and ±SEM are indicated. **, P < 0.01 versus control. Significance was determined by Student’s t test. The reversal potentials determined in these experiments did not vary significantly between groups (P > 0.7).
