The rectification of heterotypic Cx46/Cx50 gap junction channels depends on intracellular magnesium

Abstract

Gap junction (GJ) intercellular communication is crucial in many physiological and pathological processes. A GJ channel is formed by head-to-head docking of two hexameric hemichannels from two neighboring cells. Heterotypic GJ channels formed by two different homomeric connexin hemichannels often display rectification properties in the current–voltage relationship while the underlying mechanisms are not fully clear. Here we studied heterotypic Cx46/Cx50 GJs at a single GJ channel level. Our data showed unitary Cx46/Cx50 GJ channel conductance (γ_j) rectification when 5 mmol/L Mg²⁺ was included in the patch pipette solution, while no γ_j rectification was observed when no Mg²⁺ was added. Including 5 mmol/L Mg²⁺ in pipette solution significantly decreased the γ_j of homotypic Cx46 GJ with little change in homotypic Cx50 γ_j. A missense point variant in Cx46 (E43F) reduced the Mg²⁺-dependent reduction in γ_j of Cx46 E43F GJ, indicating that E43 might be partially responsible for Mg²⁺-dependent decrease in γ_j of Cx46. A comprehensive understanding of Mg²⁺ modulation of GJ at the individual channel level is useful in understanding factors in modulating GJ-mediated intercellular communication in health and diseases.

Graphical abstract

Keywords

Gap junction channel / Heterotypic gap junction / Rectification / Single channel analysis / Patch clamp