Half-calcified Calmodulin Promotes Basal Activity and Inactivation of the Calcium Channel CaV1.2.

Bartels, P.; Salveson, I. C.; Coleman, A. M.; Anderson, D.; Jeng, G.; Estrada-Tobar, Z. M.; Man, K. N. M.; Yu, Q.; Kuzmenkina, E.; Nieves-Cintron, M.; Navedo, M. F.; Horne, M. C.; Hell, J. W.; Ames, J. B.

doi:10.1101/2022.06.24.497440

bioRxiv · 10.1101/2022.06.24.497440

Half-calcified Calmodulin Promotes Basal Activity and Inactivation of the Calcium Channel CaV1.2.

Bartels, P.·Salveson, I. C.·Coleman, A. M.·Anderson, D.·Jeng, G.·Estrada-Tobar, Z. M.·Man, K. N. M.·Yu, Q.·Kuzmenkina, E.·Nieves-Cintron, M.·Navedo, M. F.·Horne, M. C.·Hell, J. W.·Ames, J. B.

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Abstract

The L-type Ca2+ channel CaV1.2 controls gene expression, cardiac contraction, and neuronal activity. Calmodulin (CaM) governs CaV1.2 open probability (Po) and Ca2+-dependent inactivation (CDI) but the mechanisms remain unclear. We identified a half Ca2+-saturated CaM species (Ca2/CaM) with Ca2+ bound solely at the third and fourth EF-hands (EF3 and EF4) under resting Ca2+ concentrations (50-100 nM) that constitutively pre-associates with CaV1.2 to promote Po and CDI. We present an NMR structure of a complex between the CaV1.2 IQ motif (residues 1644-1665) and Ca2/CaM12, a calmodulin mutant in which Ca2+ binding to EF1 and EF2 is completely disabled. The CaM12 N-lobe does not interact with the IQ motif. The CaM12 C-lobe bound two Ca2+ ions and formed close contacts with IQ residues I1654 and Y1657. I1654A and Y1657D mutations impaired CaM binding, CDI, and Po, as did disabling Ca2+ binding to EF3 and EF4 in the CaM34 mutant when compared to wildtype CaM. Accordingly, a previously unappreciated Ca2/CaM species promotes CaV1.2 Po and CDI identifying Ca2/CaM as an important mediator of Ca signaling.

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Bartels, P., Salveson, I. C., Coleman, A. M., Anderson, D., Jeng, G., Estrada-Tobar, Z. M., Man, K. N. M., Yu, Q., Kuzmenkina, E., Nieves-Cintron, M., Navedo, M. F., Horne, M. C., Hell, J. W., Ames, J. B.. 2022-06-24. Half-calcified Calmodulin Promotes Basal Activity and Inactivation of the Calcium Channel CaV1.2.. https://doi.org/10.1101/2022.06.24.497440

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