Identification of isoforms of G proteins and PKC that colocalize with tight junctions

J Membr Biol. 1996 Feb;149(3):199-209. doi: 10.1007/s002329900020.


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.

MeSH terms

  • Animals
  • Caco-2 Cells
  • Cell Line
  • Dogs
  • GTP-Binding Proteins / metabolism*
  • Humans
  • Immunoblotting
  • Microscopy, Confocal
  • Protein Kinase C / metabolism*
  • Tight Junctions / enzymology
  • Tight Junctions / metabolism*


  • Protein Kinase C
  • GTP-Binding Proteins