title: Disruption of the IS6-AID linker affects voltage-gated calcium channel inactivation and facilitation.
abstract: Two processes dominate voltage-gated calcium channel (Ca(V)) inactivation: voltage-dependent inactivation (VDI) and calcium-dependent inactivation (CDI). The Ca(V)beta/Ca(V)alpha(1)-I-II loop and Ca(2+)/calmodulin (CaM)/Ca(V)alpha(1)-C-terminal tail complexes have been shown to modulate each, respectively. Nevertheless, how each complex couples to the pore and whether each affects inactivation independently have remained unresolved. Here, we demonstrate that the IS6-alpha-interaction domain (AID) linker provides a rigid connection between the pore and Ca(V)beta/I-II loop complex by showing that IS6-AID linker polyglycine mutations accelerate Ca(V)1.2 (L-type) and Ca(V)2.1 (P/Q-type) VDI. Remarkably, mutations that either break the rigid IS6-AID linker connection or disrupt Ca(V)beta/I-II association sharply decelerate CDI and reduce a second Ca(2+)/CaM/Ca(V)alpha(1)-C-terminal-mediated process known as calcium-dependent facilitation. Collectively, the data strongly suggest that components traditionally associated solely with VDI, Ca(V)beta and the IS6-AID linker, are essential for calcium-dependent modulation, and that both Ca(V)beta-dependent and CaM-dependent components couple to the pore by a common mechanism requiring Ca(V)beta and an intact IS6-AID linker.
authors.affiliation: Cardiovascular Research Institute, Department of Biochemistry and Biophysics, California Institute for Quantitative Biosciences, University of California, San Francisco, CA 94158, USA.
authors.forename: Felix
authors.initials: F
authors.lastname: Findeisen
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Minor
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000502:physiology*; D002942:Circular Dichroism; D006801:Humans; D015640:Ion Channel Gating; D008564:Membrane Potentials / Q000502:physiology; D008969:Molecular Sequence Data; D009154:Mutation; D011485:Protein Binding; D011487:Protein Conformation; D020033:Protein Isoforms; D011817:Rabbits; D051381:Rats; D011994:Recombinant Proteins; D014981:Xenopus
chemical_list: D020746:Calcium Channels, L-Type; D020033:Protein Isoforms; D011994:Recombinant Proteins; D002118:Calcium