Basal lamina formation by epithelial cell lines correlates with laminin A chain synthesis and secretion.
Laminin is a major component of the basal lamina upon which all epithelial cells reside in vivo. The synthesis of basal lamina components and their subsequent assembly into a morphologically distinct basal lamina is a differentiated function of epithelial cells in vivo. Ultrastructural studies in our laboratory show that some epithelial cell lines (P-MDCK) form a basal lamina when cultured on membrane-permeable substrate (Millipore Millicells or type I collagen gels). Under the same conditions other epithelial cell lines (MDCK-AA7, M-mTAL-1P, and T84) do not form a basal lamina. When metabolically labeled with [35S]methionine, laminin A and B chains can be immunoprecipitated from the culture medium and culture lysates of P-MDCK cells. In contrast, labeled laminin chains cannot be immunoprecipitated from the culture medium of MDCK-AA7, M-mTAL-1P, and T84 cells. Immunoprecipitates of MDCK-AA7, M-mTAL-1P, and T84 culture lysates demonstrate the presence of one or both B chains but not A chains. These results suggest that laminin B chain synthesis is constitutive in MDCK-AA7, M-mTAL-1P, and T84 cells and that B chains, in the absence of A chains, are not secreted. Furthermore, laminin secretion and basal lamina formation are not required to maintain structural and functional polarity in these cell lines.
Ecay
T W
TW
Department of Physiology and Cell Biology, University of Texas Medical School, Houston 77225.
Valentich
J D
JD
D000818:Animals; D001485:Basement Membrane / Q000378:metabolism / Q000648:ultrastructure*; D002460:Cell Line; D003545:Cysteine / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004848:Epithelium / Q000378:metabolism / Q000648:ultrastructure; D015151:Immunoblotting; D007797:Laminin / Q000096:biosynthesis* / Q000302:isolation & purification; D046911:Macromolecular Substances; D008715:Methionine / Q000378:metabolism; D008854:Microscopy, Electron; D008970:Molecular Weight; D013462:Sulfur Radioisotopes
D007797:Laminin; D046911:Macromolecular Substances; D013462:Sulfur Radioisotopes; D008715:Methionine; D003545:Cysteine