A novel type of adhering junction in an epithelioid tumorigenic rat cell culture line.
Two major types of plaque-bearing adhering junctions are commonly distinguished: the actin microfilament-anchoring adhaerens junctions (AJs) and the desmosomes anchoring intermediate-sized filaments (IFs). Both types of junction usually possess the common plaque protein, plakoglobin, whereas the other plaque proteins and the transmembrane cadherins are mutually exclusive. For example, AJs contain E-, N-, or P-cadherin in combination with alpha- and beta-catenin, vinculin and alpha-actinin, whereas in desmosomes, desmogleins and desmocollins are associated with desmoplakin and one or several of the plakophilins (PP1-3). Here we describe a novel type of adhering junction comprising proteins of both AJs and desmosomes and the tight junction (TJ) plaque protein, ZO-1, in a newly established, liver-derived tumorigenic rat cell line (RMEC-1). By immunofluorescence microscopy, cell-cell contacts are characterized by mostly continuous-appearing lines which are usually resolved by electron microscopy as extended arrays of closely spaced small plaque subunits. These plaque-covered regions are positive for plakoglobin, alpha- and beta-catenin, the arm-repeat protein p120, vinculin, desmoplakin and protein ZO-1. They are positive for E-cadherin in cultures early on in passaging, but tend to turn negative for all known cadherins in densely grown cultures. On immunoblotting SDS-PAGE-separated proteins from dense-grown cell monolayers, "pan-cadherin" antibodies have reacted with a band at approximately 140 kDa, identified as N-cadherin by peptide fingerprinting of the immunoprecipitated protein, which for reasons not yet clear is modified or masked in immunolocalization experiments. The exact histological derivation of RMEC-1 cells is not known. However, the observations of several endothelial markers and the fact that all cells are rich in IFs containing vimentin and/or desmin, while only subpopulations also reveal IFs containing CKs 8 and 18, is suggestive of a mesenchymal, probably endothelial origin. We discuss the molecular relationship of this novel type of extended junction with other types of adhering junctions.
Department of Pathology, Martin Luther University Halle-Wittenberg, Magdeburgerstr. 14, D-06097 Halle (Saale), Germany.
M
M
Schmelz
D L
DL
Way
P
P
Borgs
W K
WK
Peitsch
H
H
Schmidt
M H
MH
Witte
C L
CL
Witte
W W
WW
Franke
R
R
Moll
D000818:Animals; D015820:Cadherins / Q000378:metabolism; D015815:Cell Adhesion Molecules / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000378:metabolism; D051187:Desmocollins; D051182:Desmogleins; D051180:Desmoplakins; D003896:Desmosomes / Q000378:metabolism / Q000648:ultrastructure; D007365:Intercellular Junctions / Q000378:metabolism* / Q000648:ultrastructure*; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008819:Mice, Nude; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D009374:Neoplasms, Experimental / Q000378:metabolism / Q000473:pathology; D010750:Phosphoproteins / Q000378:metabolism; D051381:Rats; D015534:Trans-Activators; D014407:Tumor Cells, Cultured; D016596:Vinculin / Q000378:metabolism; D062826:Zonula Occludens-1 Protein; D051178:alpha Catenin; D051176:beta Catenin; D051185:gamma Catenin
C495267:CTNNB1 protein, mouse; D015820:Cadherins; D015815:Cell Adhesion Molecules; C495272:Ctnna1 protein, mouse; C495268:Ctnnb1 protein, rat; D003598:Cytoskeletal Proteins; D051187:Desmocollins; D051182:Desmogleins; D051180:Desmoplakins; C495295:Dsp protein, mouse; D008565:Membrane Proteins; D010750:Phosphoproteins; C569043:Tjp1 protein, mouse; C569044:Tjp1 protein, rat; D015534:Trans-Activators; D062826:Zonula Occludens-1 Protein; D051178:alpha Catenin; D051176:beta Catenin; D051185:gamma Catenin; D016596:Vinculin