Apparent lack of physical or functional interaction between CaV1.1 and its distal C terminus.
Bottom Line: It has been proposed that, after its posttranslational cleavage, the distal C terminus of CaV1.1 remains noncovalently associated with proximal CaV1.1, and that tethering of protein kinase A to the distal C terminus is required for depolarization-induced potentiation of L-type Ca(2+) current in skeletal muscle.We found that L-type Ca(2+) channel activity was similar after expression of constructs that either did (YFP-CaV1.11860) or did not (YFP-CaV1.11666) contain coding sequence for the distal C-terminal domain in dysgenic myotubes for endogenous CaV1.1.Thus, our experiments do not support the existence of either biochemical or functional interactions between proximal CaV1.1 and the distal C terminus.
Affiliation: Department of Physiology and Biophysics and Department of Medicine-Cardiology Division, University of Colorado, Denver, Aurora, CO 80045.Show MeSH
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Mentions: To analyze the depolarization-induced potentiation of the skeletal L-type Ca2+ current, we used two voltage protocols that were similar to those used in previous work (Johnson et al., 1994, 1997). In one protocol (Fig. 6 A, top), 200-ms steps to increasingly depolarized potentials were applied, followed by repolarization to elicit inward tail current. In the other protocol (Fig. 6 B, top), the duration of a depolarization to 90 mV was varied from 50 to 200 ms, before repolarization. As shown in Fig. 6, tail current amplitude was increased and decay time slowed when the prepulse depolarization was made either larger (Fig. 6, A and B) or longer (Fig. 6, C and D). This behavior is similar to that described previously for myotubes produced from the 129CB3 line of immortalized mouse myoblasts (Johnson et al., 1994, 1997). Importantly, the effects of increased prepulse amplitude, and of increased prepulse duration, were qualitatively similar in dysgenic myotubes expressing either CaV1.11860 or CaV1.11666.
Affiliation: Department of Physiology and Biophysics and Department of Medicine-Cardiology Division, University of Colorado, Denver, Aurora, CO 80045.