REGULATION OF GAP-JUNCTIONS BY PROTEIN-PHOSPHORYLATION

Gap junctions are constituted by intercellular channels and provide a pathway for transfer of ions and small molecules between adjacent cell s of most tissues. The degree of intercellular coupling mediated by ga p junctions depends on the number of gap junction channels and their a ctivity may be a function of the state of phosphorylation of connexins , the structural subunit of gap junction channels. Protein phosphoryla tion has been proposed to control intercellular gap junctional communi cation at several steps from gene expression to protein degradation, i ncluding translational and post-translational modification of connexin s (i.e., phosphorylation of the assembled channel acting as a gating m echanism) and assembly into and removal from the plasma membrane. Seve ral connexins contain sites for phosphorylation for more than one prot ein kinase. These consensus sites vary between connexins and have been preferentially identified in the C-terminus, Changes in intercellular communication mediated by protein phosphorylation are believed to con trol various physiological tissue and cell functions as well as to be altered under pathological conditions.