Mutations of nonconserved residues within the calcium channel alpha(1)-interaction domain inhibit beta-subunit potentiation
Voltage-dependent calcium channels consist of a pore-forming subunit (CaVÎ±1) that includes all the molecular determinants of a voltage-gated channel, and several accessory subunits. The ancillary Î²-subunit (CaVÎ²) is a potent activator of voltage-dependent calcium channels, but the mechanisms and structural bases of this regulation remain elusive. CaVÎ² binds reversibly to a conserved consensus sequence in CaVÎ±1, the Î±1- interaction domain (AID), which forms an Î±-helix when complexed with CaVÎ². Conserved aromatic residues face to one side of the helix and strongly interact with a hydrophobic pocket on CaVÎ². Here, we studied the effect of mutating residues located opposite to the AID-Ca VÎ² contact surface in CaV1.2. Substitution of AID-exposed residues by the corresponding amino acids present in other Ca VÎ±1 subunits (E462R, K465N, D469S, and Q473K) hinders CaVÎ²'s ability to increase ionic-current to charge-movement ratio (I/Q) without changing the apparent affinity for Ca VÎ². At the single channel level, these CaV1.2 mutants coexpressed with CaVÎ²2a visit high open probability mode less frequently than wildtype channels. On the other hand, Ca V1.2 carrying either a mutation in the conserved tryptophan residue (W470S, which impairs CaVÎ² binding), or a deletion of the whole AID sequence, does not exhibit CaVÎ²-induced increase in I/Q. In addition, we observed a shift in the voltage dependence of activation by +12 mV in the AID-deleted channel in the absence of CaVÎ², suggesting a direct participation of these residues in the modulation of channel activation. Our results show that CaVÎ²-dependent potentiation arises primarily from changes in the modal gating behavior. We envision that Ca VÎ² spatially reorients AID residues that influence the channel gate. These findings provide a new framework for understanding modulation of VDCC gating by CaVÎ². Â© 2008 Gonzales-Gutierrez et al.
|Título según WOS:||Mutations of nonconserved residues within the calcium channel alpha(1)-interaction domain inhibit beta-subunit potentiation|
|Título según SCOPUS:||Mutations of nonconserved residues within the calcium channel a1-interaction domain inhibit ß-subunit potentiation|
|Título de la Revista:||JOURNAL OF GENERAL PHYSIOLOGY|
|Editorial:||ROCKEFELLER UNIV PRESS|
|Fecha de publicación:||2008|
|Página de inicio:||383|