The Hydrophobic Residues in Amino Terminal Domains of Cx46 and Cx50 are Important for their Gap Junction Channel Ion Permeation and Gating

Roa'a Jaradat, The University of Western Ontario

Abstract

Connexins are ubiquitous transmembrane proteins that assemble to form intercellular channels, called gap junctions (GJs). The amino terminal (NT) domain and residues within this domain have been shown to be important for both V_j-gating and single channel conductance (γ_j) of several GJs including Cx46 and Cx50. High-resolution structures of Cx46 and Cx50 GJs were recently resolved showing that NT domain folds into the inner pore where hydrophobic residues are packed against M1/2 domains stabilizing open-state conformation. We studied functional properties of GJs formed by several point variants at NT (Cx46 L10I, N13E, A14V, Q15N and Cx50 I10L, E13N, V14A, N15Q) and M2 domain (Cx50 S89T) in GJ-deficient N2A cells. We found that these variants formed functional GJs except Cx50 S89T. Altered coupling conductance, γ_j, and/or V_j-gating observed in GJs of L10I and A14V indicate these hydrophobic residues are important for V_j-gating and γ_j of these and possibly other GJs.