Identification of isoforms of G proteins and PKC that colocalize with tight junctions.
Recent evidence suggests that the formation and permeability of tight junctions are actively regulated by second-messenger-generating systems involving G proteins and protein kinase C (PKC). A possible specific target for these regulatory proteins is the tight junction protein ZO-1. An extensive immunocytochemical study was performed in cultured epithelial monolayers of MDCK and Caco-2 cells to identify which isoforms of G proteins and PKC are present at or near zonula occludens complex. Antibodies against alpha-subunits of each one of the four major subfamilies were used for the localization of the G proteins. For the PKC localization, antibodies against eight different isoforms were used. In confluent monolayers, G alpha 12 and PKC zeta, were the only isoforms of these proteins at the cell borders. In subconfluent monolayers, G alpha 12 and PKC zeta were found at the plasma membrane only along the areas of lateral cell-cell contact. These isoforms formed a pattern of distribution very similar to the ZO-1 protein. The present findings indicate that G alpha 12 and PKC zeta may be part of the zonula occludens complex and may locally regulate formation and permeability of tight junctions.
Dodane
V
V
Laboratory of Cellular Biology, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Rockville, MD 20850, USA.
Kachar
B
B
D000818:Animals; D018938:Caco-2 Cells; D002460:Cell Line; D004285:Dogs; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D015151:Immunoblotting; D018613:Microscopy, Confocal; D011493:Protein Kinase C / Q000378:metabolism*; D019108:Tight Junctions / Q000201:enzymology / Q000378:metabolism*
D011493:Protein Kinase C; D019204:GTP-Binding Proteins