Gap junction protein that acts as a regulator of bladder capacity. A gap junction consists of a cluster of closely packed pairs of transmembrane channels, the connexons, through which materials of low MW diffuse from one cell to a neighboring cell. May play a critical role in the physiology of hearing by participating in the recycling of potassium to the cochlear endolymph. Negative regulator of bladder functional capacity: acts by enhancing intercellular electrical and chemical transmission, thus sensitizing bladder muscles to cholinergic neural stimuli and causing them to contract. May play a role in cell growth inhibition through the regulation of NOV expression and localization. Plays an essential role in gap junction communication in the ventricles (By similarity). A connexon is composed of a hexamer of connexins. Interacts with SGSM3 (By similarity). Interacts with RIC1/CIP150 (By similarity). Interacts with CNST and CSNK1D (By similarity). Interacts (via C-terminus) with TJP1. Interacts (via C-terminus) with SRC (via SH3 domain). Interacts (not ubiquitinated) with UBQLN4 (via UBA domain) (By similarity). Interacts with NOV. Interacts with TMEM65 (By similarity). Localizes at the intercalated disk (ICD) in cardiomyocytes and proper localization at ICD is dependent on TMEM65. Phosphorylation at Ser-325, Ser-328 and Ser-330 by CK1 modulates gap junction assembly (By similarity). Phosphorylated at Ser-368 by PRKCG; phosphorylation induces disassembly of gap junction plaques and inhibition of gap junction activity. Phosphorylation at Ser-368 by PRKCD triggers its internalization into small vesicles leading to proteasome-mediated degradation (By similarity). Sumoylated with SUMO1, SUMO2 and SUMO3, which may regulate the level of functional Cx43 gap junctions at the plasma membrane. May be desumoylated by SENP1 or SENP2 (By similarity). S-nitrosylation at Cys-271 is enriched at the muscle endothelial gap junction in arteries, it augments channel permeability and may regulate of smooth muscle cell to endothelial cell communication. Acetylated in the developing cortex; leading to delocalization from the cell membrane. Belongs to the connexin family. Alpha-type (group II) subfamily.