Structure of native lens connexin 46/50 intercellular channels by cryo-EM.

Abstract

Gap junctions establish direct pathways for cell-to-cell communication, through the assembly of twelve subunits (connexins) that form intercellular channels connecting neighboring cells. Co-assembly of different connexin isoforms produces channels with unique properties, and enables communication across cell-types. To gain access into the structural underpinnings of connexin co-assembly, we used single particle CryoEM to determine the structure of native lens gap junction channels, composed of connexin-46 and connexin-50 (Cx46/50). We provide the first comparative analysis to connexin-26 (Cx26), which together with computational studies elucidates key energetic features governing gap junction perm-selectivity. Cx46/50 adopts an open-state conformation that is unique from the Cx26 crystal structure, yet appears to be stabilized by a conserved set of hydrophobic anchoring residues. ‘Hot spots’ of genetic mutations linked to hereditary cataract formation map to the core structural-functional elements identified in Cx46/50, rationalizing many of the disease-causing effects.