Allosteric regulators selectively prevent Ca2+-feedback of CaV and NaV channels.

Jacqueline Niu,Gordon Tomaselli,David T Yue,Takanari Inoue,Ivy E Dick,Wanjun Yang,Manu Ben-Johny,Moradeke A Bamgboye

doi:10.7554/elife.35222

Jacqueline Niu, Gordon Tomaselli + Show 6 more

Open Access

https://doi.org/10.7554/elife.35222

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Abstract

Calmodulin (CaM) serves as a pervasive regulatory subunit of CaV1, CaV2, and NaV1 channels, exploiting a functionally conserved carboxy-tail element to afford dynamic Ca2+-feedback of cellular excitability in neurons and cardiomyocytes. Yet this modularity counters functional adaptability, as global changes in ambient CaM indiscriminately alter its targets. Here, we demonstrate that two structurally unrelated proteins, SH3 and cysteine-rich domain (stac) and fibroblast growth factor homologous factors (fhf) selectively diminish Ca2+/CaM-regulation of CaV1 and NaV1 families, respectively. The two proteins operate on allosteric sites within upstream portions of respective channel carboxy-tails, distinct from the CaM-binding interface. Generalizing this mechanism, insertion of a short RxxK binding motif into CaV1.3 carboxy-tail confers synthetic switching of CaM regulation by Mona SH3 domain. Overall, our findings identify a general class of auxiliary proteins that modify Ca2+/CaM signaling to individual targets allowing spatial and temporal orchestration of feedback, and outline strategies for engineering Ca2+/CaM signaling to individual targets.

Highlights

Supporting vital biological functions, voltage-gated calcium (CaV1 and CaV2) and sodium (NaV1) channels are tuned by the Ca2+-binding protein, calmodulin (CaM) (Ben-Johny et al, 2015; Catterall et al, 2017; Saimi and Kung, 2002)
Our findings point to a general class of auxiliary proteins that intercept CaM signaling to individual targets, allowing spatial and temporal orchestration of Ca2+-feedback
CaV1.2 exhibits CaM-mediated CDI manifesting as enhanced decay of Ca2+ versus Ba2+ current when elicited using a step depolarization (Figure 1A, middle subpanel)

Summary

Introduction

Supporting vital biological functions, voltage-gated calcium (CaV1 and CaV2) and sodium (NaV1) channels are tuned by the Ca2+-binding protein, calmodulin (CaM) (Ben-Johny et al, 2015; Catterall et al, 2017; Saimi and Kung, 2002). NaV1 supports action potential initiation and propagation (Hille, 2001), while CaV1/2 initiate muscle contraction, neurotransmission, and gene transcription (Berridge et al, 2000; Clapham, 2007; Maier and Bers, 2002) Despite divergent functions, these channel families share a conserved carboxy-tail element, termed Ca2+-inactivating (CI) module, that harbors CaM. The CI module confers dynamic Ca2+-dependent regulation to CaV1, CaV2, and NaV1 that manifests as either inactivation (CDI) or facilitation (CDF), negative and positive feedback, respectively (Ben-Johny et al, 2015; Minor and Findeisen, 2010) This modularity poses a challenge – mechanisms that tune Ca2+/CaM-feedback must distinguish between structurally similar targets. Our findings point to a general class of auxiliary proteins that intercept CaM signaling to individual targets, allowing spatial and temporal orchestration of Ca2+-feedback

Results

Discussion

Materials and methods

Funding Funder National Science Foundation