DISPERSED AND AGGREGATED GAP JUNCTION CHANNELS IDENTIFIED BY IMMUNOGOLD LABELING OF FREEZE-FRACTURED MEMBRANES

An indirect immunogold labeling technique was applied to replicas of f reeze-fractured membranes of rapidly frozen unfixed cells. The endogen ous gap junction protein Cx43 of BICR/M1R(k) rat mammary tumor cells w as preferentially identified in quasi-crystalline gap junction plaques as were the transfected connexins Cx40, Cx43, and Cx45 in HeLa (human cervical carcinoma) cells. With this method we also detected contact areas with dispersed gap junction channels which are the only structur al correlation for endogenous Cx45 in HeLa wild-type cells where no ga p junction plaques exist. In double-transfected HeLa cells a colocaliz ation of Cx40 and Cx43 was occasionally detected in quasicrystalline g ap junction plaques, whereas in contact areas with dispersed particles only one Cx type was present. Our results indicate that functional ga p junction channels exist outside the quasi-crystalline plaques, (C) 1 997 Academic Press.