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Basal lamina formation by epithelial cell lines correlates with laminin A chain synthesis and secretion

1992; Elsevier BV; Volume: 203; Issue: 1 Linguagem: Inglês

10.1016/0014-4827(92)90036-8

1090-2422

Tom W. Ecay, J. D. Valentich,

Skin and Cellular Biology Research

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 substrata (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.