PMID: 30944319

Authors:

Yoder JB, Ben-Johny M, Farinelli F, Srinivasan L, Shoemaker SR, Tomaselli GF, Gabelli SB, Amzel LM

Title:

Ca(2+)-dependent regulation of sodium channels NaV1.4 and NaV1.5 is controlled by the post-IQ motif.

Journal:

Nat Commun. 2019 Apr 3;10(1):1514. doi: 10.1038/s41467-019-09570-7.

Abstract:

Skeletal muscle voltage-gated Na(+) channel (NaV1.4) activity is subject to calmodulin (CaM) mediated Ca(2+)-dependent inactivation; no such inactivation is observed in the cardiac Na(+) channel (NaV1.5). Taken together, the crystal structures of the NaV1.4 C-terminal domain relevant complexes and thermodynamic binding data presented here provide a rationale for this isoform difference. A Ca(2+)-dependent CaM N-lobe binding site previously identified in NaV1.5 is not present in NaV1.4 allowing the N-lobe to signal other regions of the NaV1.4 channel. Consistent with this mechanism, removing this binding site in NaV1.5 unveils robust Ca(2+)-dependent inactivation in the previously insensitive isoform. These findings suggest that Ca(2+)-dependent inactivation is effected by CaM's N-lobe binding outside the NaV C-terminal while CaM's C-lobe remains bound to the NaV C-terminal. As the N-lobe binding motif of NaV1.5 is a mutational hotspot for inherited arrhythmias, the contributions of mutation-induced changes in CDI to arrhythmia generation is an intriguing possibility.