Composed of connexins, gap junctions are important for intercellular transfer of ions and small molecules. Although it is known that mutations in the connexin 30 (Cx30)-encoding gene cause skin disease and hearing loss, Cx30 is still poorly characterised. Here, Dale Laird and colleagues (p. ), therefore, investigate the trafficking, stability and cell surface dynamics of this understudied connexin. They observe slow turnover of Cx30 gap junction plaques, and find that new Cx30 junctions are added at the outer edges of the plaques. Blocking endoplasmic reticulum (ER)-to-Golgi transport with brefeldin A further confirms the increased stability of Cx30, as it remains at the cell surface, whereas Cx43 and Cx26 are rapidly cleared. Using cycloheximide to inhibit protein synthesis, the authors calculate the half-life of Cx30 to be ∼12h, which is unusually long compared with most known connexins. Of note, Cx30 also accumulates in the ER in brefeldin-A-treated cells, indicating that it traffics to the plasma membrane through the traditional ER-to-Golgi secretory pathway. In support of this, blocking COPII coat assembly by expression of a dominant-negative Sar1 GTPase mutant also results in Cx30 ER accumulation. Finally, when Cx30 and Cx43 are co-expressed within the same plaque they are restricted to separate regions, as would be expected from their vastly different half-lives and dynamics. Taken together, these results provide important new insights into the life cycle and dynamics of Cx30 that will be of great value to understanding its role in hearing and function in the skin.
