The Skin Disease Mutation Cx31L209F Induces a Calcium- and Cobalt-Sensitive Leak Current Across the Plasma Membrane

Gap junctions are essential to the function of multicellular animals, which require a high degree of coordination between cells. The functions of gap junctions are highly diverse and include exchange of metabolites and electrical signals between cells, as well as functions apparently unrelated to intercellular communication. In vertebrates, gap junctions are comprised of connexin proteins and over 20 connexins have been identified in humans. Each connexin is named according to its predicted molecular weight, for instance connexin31 (Cx31) has a predicted molecular weight of 31 KDa. Mutations in connexin genes cause a variety of disorders depending on the connexin protein affected. Cx31 is one of the gap junction proteins expressed in skin and the inner ear. Some point mutations cause a rare skin disease termed erythrokeratodermia variabilis (EKV) whereas other mutations cause non-syndromic hearing loss (NSHL). The main goal of this project was to create, express and study Cx31L209F, a hereditary skin disease mutation which occurs in the fourth transmembrane domain. Other mutations (S26T, C86S and L135V) were also briefly studied. The L209F mutant induced large membrane currents and compromised the health of single cells suggesting that aberrant hemichannel behavior may underlie the disease pathology. Cell death in L209F-expressing cells was rescued by the addition of 2 mM calcium or 1 mM cobalt, conditions known to block hemichannel function. Two of the other mutations S26T, and L135V appeared to form gap junctions with altered gating properties