Characterization of the gap junction protein connexin37 in murine endothelium, respiratory epithelium, and after transfection in human HeLa cells

Affinity-purified antibodies to oligopeptides derived from two different re gions of the carboxyterminus and cytoplasmic loop or to the last 103 C-term inal amino acids of mouse connexin37 (Cx37) were used to characterize expre ssion of this gap junctional protein in endothelium of several murine tissu es. Cx37 was expressed in endothelium of large blood vessels in brain, live r, kidney, spleen, heart, and lung, but not in capillaries. In addition, we ak Cx37 immune-signals were observed in lung respiratory epithelium of smal l bronchi and in alveolar epithelial cells of bronchioli. The ratios of Cx3 7 protein to Cx37 mRNA in adult and embryonic kidney as well as skin were 2 9-303-fold larger than in lung, suggesting that Cx37 mRNA was translated at different efficiencies in kidney and skin versus lung. Cx37 protein was mo re abundant in embryonic kidney and lung than in the corresponding adult ti ssues. After differential, centrifugation of plasma membrane fractions in s ucrose gradients, we found that Cx37-containing gap junctions in lung were much smaller than Cx32 and Cx26 aggregates from Liver. HeLa cells were tran sfected with mouse Cx37 cDNA. In these cells, mouse. Cx37 protein was phosp horylated mainly at serine, less at tyrosine, and very little at threonine residues. Three conductance states were resolved at 110, 240, and 315 pS.