Structure-based site-directed photo-crosslinking analyses of multimeric cell-adhesive interactions of voltage-gated sodium channel β subunits

Abstract

The β1, β2, and β4 subunits of voltage-gated sodium channels reportedly function as cell adhesion molecules. The present crystallographic analysis of the β4 extracellular domain revealed an antiparallel arrangement of the β4 molecules in the crystal lattice. The interface between the two antiparallel β4 molecules is asymmetric, and results in a multimeric assembly. Structure-based mutagenesis and site-directed photo-crosslinking analyses of the β4-mediated cell-cell adhesion revealed that the interface between the antiparallel β4 molecules corresponds to that in the trans homophilic interaction for the multimeric assembly of β4 in cell-cell adhesion. This trans interaction mode is also employed in the β1-mediated cell-cell adhesion. Moreover, the β1 gene mutations associated with generalized epilepsy with febrile seizures plus (GEFS+) impaired the β1-mediated cell-cell adhesion, which should underlie the GEFS+ pathogenesis. Thus, the structural basis for the β-subunit-mediated cell-cell adhesion has been established.

Supramolecular clustering of the cardiac sodium channel Nav1.5 in HEK293F cells, with and without the auxiliary β3‐subunit

“…Cis ‐interactions have also been characterized for the Nav channel β4‐subunit, independently of its binding to Nav channels. In this case, the cis‐interactions between β4‐subunits facilitate trans‐cell adhesion behavior . The β3‐subunit has also been shown to promote trans ‐cell adhesion, at least under conditions of high expression .…”

“…In this case, the cis-interactions between β4-subunits facilitate trans-cell adhesion behavior. [20][21][22] The β3-subunit has also been shown to promote trans-cell adhesion, at least under conditions of high expression. 19 Hence, the ability of β3subunits to homo-trimerize may reflect a more general tendency of Nav channel β-subunits to self-assemble, at least under some in vivo conditions-for example, in the absence of Nav α-subunits.…”

Voltage-Gated Sodium Channel β Subunits and Their Related Diseases

“…The function of β4 in cell adhesion remains more poorly understood (Brackenbury and Isom 2011). Insights from crystallographic, mutagenic, and photo-crosslinking studies have revealed the structural importance of an antiparallel interface between β4 subunits in trans homophilic adhesion (Shimizu et al 2016). Recent evidence shows that β4 Ig domains interact in a parallel manner involving a disulfide bond between cysteine 58 and hydrophobic and hydrogen bonding interactions between residues 30 through 35.…”

Crystal structures of Ca 2+ –calmodulin bound to Na V C-terminal regions suggest role for EF-hand domain in binding and inactivation

“…Recent advances in cryo-EM have allowed reconstructions of Na V 1.4 from electric eels (3) and humans (4) and an Na v from the American cockroach (5). In addition, high-resolution crystal structures have been reported for the Ig domains of mammalian Na V β2, β3, and β4 (6)(7)(8)(9). Despite these advances, the bulk of the cytosolic region appeared invisible in the cryo-EM reconstructions, suggesting inherent flexibility relative to the TM region.…”