Ca2+-saturated calmodulin binds tightly to the N-terminal domain of A-type fibroblast growth factor homologous factors

Ryan Mahling; Cade R Rahlf; Samuel C Hansen; Matthew R Hayden; Madeline A Shea

doi:10.1016/j.jbc.2021.100458

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Ca2+-saturated calmodulin binds tightly to the N-terminal domain of A-type fibroblast growth factor homologous factors

Journal article

Open access

Peer reviewed

Ca2+-saturated calmodulin binds tightly to the N-terminal domain of A-type fibroblast growth factor homologous factors

Ryan Mahling, Cade R Rahlf, Samuel C Hansen, Matthew R Hayden and Madeline A Shea

The Journal of biological chemistry, Vol.296, pp.100458-100458

2021

DOI: 10.1016/j.jbc.2021.100458

PMCID: PMC8059062

PMID: 33639159

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Abstract

Voltage-gated sodium channels (Navs) are tightly regulated by multiple conserved auxiliary proteins, including the four fibroblast growth factor homologous factors (FGFs), which bind the Nav EF-hand like domain (EFL), and calmodulin (CaM), a multifunctional messenger protein that binds the NaV IQ motif. The EFL domain and IQ motif are contiguous regions of NaV cytosolic C-terminal domains (CTD), placing CaM and FGF in close proximity. However, whether the FGFs and CaM act independently, directly associate, or operate through allosteric interactions to regulate channel function is unknown. Titrations monitored by steady-state fluorescence spectroscopy, structural studies with solution NMR, and computational modeling demonstrated for the first time that both domains of (Ca2+)4-CaM (but not apo CaM) directly bind two sites in the N-terminal domain (NTD) of A-type FGF splice variants (FGF11A, FGF12A, FGF13A, and FGF14A) with high affinity. The weaker of the (Ca2+)4-CaM-binding sites was known via electrophysiology to have a role in long-term inactivation of the channel but not known to bind CaM. FGF12A binding to a complex of CaM associated with a fragment of the NaV1.2 CTD increased the Ca2+-binding affinity of both CaM domains, consistent with (Ca2+)4-CaM interacting preferentially with its higher-affinity site in the FGF12A NTD. Thus, A-type FGFs can compete with NaV IQ motifs for (Ca2+)4-CaM. During spikes in the cytosolic Ca2+ concentration that accompany an action potential, CaM may translocate from the NaV IQ motif to the FGF NTD, or the A-type FGF NTD may recruit a second molecule of CaM to the channel.

Molecular Recognition

Thermodynamics

NMR

Ca2+-dependent interaction

biosensor

FHF

protein–protein interaction

FRET

voltage-gated sodium channel

allostery

affinity

Details

Title: Subtitle: Ca2+-saturated calmodulin binds tightly to the N-terminal domain of A-type fibroblast growth factor homologous factors
Creators: Ryan Mahling
Cade R Rahlf
Samuel C Hansen
Matthew R Hayden
Madeline A Shea
Resource Type: Journal article
Publication Details: The Journal of biological chemistry, Vol.296, pp.100458-100458
DOI: 10.1016/j.jbc.2021.100458
PMID: 33639159
PMCID: PMC8059062
NLM abbreviation: J Biol Chem
ISSN: 0021-9258
eISSN: 1083-351X
Publisher: Elsevier Inc
Grant note: DOI: 10.13039/100008893, name: University of Iowa; DOI: 10.13039/100015515, name: University of Iowa Roy J and Lucille A Carver College of Medicine; DOI: 10.13039/100000002, name: National Institutes of Health
Language: English
Date published: 2021
Academic Unit: Molecular Physiology and Biophysics; Iowa Neuroscience Institute; Biochemistry and Molecular Biology
Record Identifier: 9984070553902771

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