ZO-1 and cingulin: tight junction proteins with distinct identities and localizations.
The relative localization of ZO-1 and cingulin, the only two known components of the tight junction, was compared in Madin-Darby canine kidney (MDCK) cells, chicken small intestine, rat kidney distal convoluted tubule, and a hepatoma cell line. Immunoblot analysis demonstrated that cingulin and ZO-1 are immunologically unrelated and that, in the colon, cingulin is a single polypeptide with a molecular mass of 140 kDa. Immunofluorescent localization of cingulin and ZO-1 in confluent monolayers of MDCK cells showed identical staining patterns. However, subconfluent MDCK cells showed distinct localizations of the two proteins. Both cingulin and ZO-1 were found at the plasma membrane only at areas of cell-cell contact, but cingulin was diffusely distributed within the cytoplasm, whereas ZO-1 showed a more clustered internal arrangement. Cingulin and ZO-1 were identically localized at the plasma membrane of hepatoma tissue culture (HTC) cells at sites of cell-cell contact. In chicken intestine examined at the ultrastructural level, immunogold particles associated with cingulin were found approximately three times farther from the junctional membrane than those affiliated with ZO-1.
Stevenson
B R
BR
Department of Biology, Yale University School of Medicine, New Haven, Connecticut 06511.
Heintzelman
M B
MB
Anderson
J M
JM
Citi
S
S
Mooseker
M S
MS
D000818:Animals; D000911:Antibodies, Monoclonal; D002460:Cell Line; D002645:Chickens; D004386:Duodenum / Q000648:ultrastructure; D005455:Fluorescent Antibody Technique; D007365:Intercellular Junctions / Q000032:analysis / Q000648:ultrastructure*; D007668:Kidney; D007686:Kidney Tubules, Distal / Q000648:ultrastructure; D008114:Liver Neoplasms, Experimental; D008565:Membrane Proteins / Q000032:analysis* / Q000276:immunology; D008854:Microscopy, Electron; D008871:Microvilli / Q000648:ultrastructure; D009130:Muscle, Smooth / Q000648:ultrastructure; D010750:Phosphoproteins / Q000032:analysis* / Q000276:immunology; D051381:Rats; D062826:Zonula Occludens-1 Protein
D000911:Antibodies, Monoclonal; D008565:Membrane Proteins; D010750:Phosphoproteins; C569044:Tjp1 protein, rat; D062826:Zonula Occludens-1 Protein