Crystal Structure of the Ternary Complex of a NaV C-Terminal Domain, a Fibroblast Growth Factor Homologous Factor, and Calmodulin

Abstract

Summary Voltage-gated Na+ (NaV) channels initiate neuronal action potentials. NaV channels are composed of a transmembrane domain responsible for voltage-dependent Na+ conduction and a cytosolic C-terminal domain (CTD) that regulates channel function through interactions with many auxiliary proteins, including fibroblast growth factor homologous factors (FHFs) and calmodulin (CaM). Most ion channel structural studies have focused on mechanisms of permeation and voltage-dependent gating but less is known about how intracellular domains modulate channel function. Here we report the crystal structure of the ternary complex of a human NaV CTD, an FHF, and Ca2+-free CaM at 2.2 Å. Combined with functional experiments based on structural insights, we present a platform for understanding the roles of these auxiliary proteins in NaV channel regulation and the molecular basis of mutations that lead to neuronal and cardiac diseases. Furthermore, we identify a critical interaction that contributes to the specificity of individual NaV CTD isoforms for distinctive FHFs.

Polarized localization of voltage-gated Na + channels is regulated by concerted FGF13 and FGF14 action

“…2 D-F). These data suggest different targeting sites for FGF13 and FGF14 within the AIS, which is remarkable, given the degree of sequence similarity between these two FHFs, particularly within their FGF-like core domains that contain their VGSC binding sites (19,35,36). Together, the distinct localization patterns of FGF13 and FGF14 suggested different roles for these FHFs within hippocampal neurons.…”

“…Among the intracellular VGSC regulators are the FGF homologous factors (FHFs), noncanonical members of the FGF superfamily that are neither secreted nor appear to function as growth factors (15)(16)(17)(18). Rather, the four FHFs (FGF11-FGF14) each contain a VGSC interaction site within a homologous FGF-like core domain (19,20) and exert variable effects on VGSC functional properties (21)(22)(23). The importance of FHFs is underscored by loss-of-function or dominant negative mutations in specific FHFs associated with various neurological disorders, which have been attributed, at least in part, to VGSC dysfunction.…”

Brugada syndrome and cardiac sodium channelopathy overlap syndromes: different faces of SCN5A mutations

“…Известно, что проксимальная половина С-конца содержит шесть спиральных структур (H1-H6), которые имеют решающее значение для установления межцепочечных контактов, а также внутримолекулярных взаимодействий с линкером доменов III и IV, стабилизирующих инактивированное состояние [39]. Мутация E1823HfsX10 усекает С-конец за счет удаления H3-H6, оставляя H1 и H2 неизменными, что может способствовать различиям в вариантах пропускной способности, объясняющим разно-образие клинических проявлений в обследован-ной семье.…”

Crystallographic analysis of theArabidopsis thalianaBAG5–calmodulin protein complex

“…# 2015 International Union of Crystallography conformation the hydrophobic residues in each lobe are buried and held together, which precludes further substrate binding; however, calcium saturation triggers a significant change in the orientation of the helices in two lobes, and this change eventually leads to an 'open' conformation with exposed hydrophobic clefts (Houdusse et al, 2006;Wang et al, 2012). This structural change enables CaM to induce signal transduction pathways that act downstream of the initial detection of the second messenger Ca 2+ (Zielinski, 1998).…”

“…CaM conveys stimuli signals through alterations in its own structure in response to calcium binding (Snedden & Fromm, 1998;Zielinski, 1998). Previous structural studies on CaM under different conditions have revealed that CaM adopts a 'closed' conformation in the calcium-free state but adopts an 'open' conformation following calcium binding (Feldkamp et al, 2011;Wang et al, 2012). In the 'closed'…”