Molecular environment of ZO-1 in epithelial and non-epithelial cells.
We previously reported the expression of ZO-1 in cell types that do not form tight junctions. Here we compare the molecular environments of ZO-1 in epithelial cells, primary cultures of astrocytes and in the non-epithelial S180 sarcoma cell line. ZO-1 co-localizes with a subset of actin filaments in all cell types. In astrocytes, ZO-1 is found concentrated in discrete bands at points of cell-cell contact. Indirect immunofluorescent microscopy shows that these bands of ZO-1 co-localize with the adherens junction proteins vinculin and alpha-actinin, and with the antigen recognized by a pan-cadherin antibody. In contrast, ZO-1 in S180 cells, which exhibit limited cell-cell interactions, is diffusely distributed over the plasma membrane, with concentrations in lamellipodia where actin filaments accumulate. ZO-1 does not co-localize with vinculin at focal adhesions in this cell type. Analysis of ZO-1 immunoprecipitation profiles from different cell types, performed under conditions previously demonstrated to maintain interactions between ZO-1, ZO-2 and p130 from the MDCK epithelial cell line, show that the proteins which co-precipitate with ZO-1 vary with cell type. Precipitation of polypeptides at 165 kDa, potentially ZO-2, and 65 kDa occurs in both a mouse kidney tubule epithelial cell line and the non-epithelial S180 cells. No proteins specifically associate with ZO-1 immunoprecipitated from astrocytes. Spectrin, alpha-actinin, vinculin and cadherin are not detected in immunoblots of ZO-1 immunoprecipitates from any cell type.
Howarth
A G
AG
Department of Anatomy and Cell Biology, University of Alberta, Edmonton, Canada.
Stevenson
B R
BR
D000185:Actinin / Q000032:analysis; D000199:Actins / Q000032:analysis*; D000818:Animals; D001253:Astrocytes / Q000737:chemistry* / Q000648:ultrastructure; D015820:Cadherins / Q000032:analysis; D002118:Calcium / Q000502:physiology; D002462:Cell Membrane / Q000737:chemistry*; D002478:Cells, Cultured; D004285:Dogs; D004847:Epithelial Cells; D007365:Intercellular Junctions / Q000737:chemistry*; D008565:Membrane Proteins / Q000032:analysis*; D051379:Mice; D010750:Phosphoproteins / Q000032:analysis*; D011554:Pseudopodia / Q000737:chemistry; D012510:Sarcoma 180; D014407:Tumor Cells, Cultured; D016596:Vinculin / Q000032:analysis; D062826:Zonula Occludens-1 Protein; D062827:Zonula Occludens-2 Protein
D000199:Actins; D015820:Cadherins; D008565:Membrane Proteins; D010750:Phosphoproteins; C569043:Tjp1 protein, mouse; C569047:Tjp2 protein, mouse; D062826:Zonula Occludens-1 Protein; D062827:Zonula Occludens-2 Protein; D000185:Actinin; D016596:Vinculin; D002118:Calcium