Cell adhesion to a population of laminin isoforms isolated from normal renal tissue

To assess whether cells react differently towards a population of several l aminin isoforms, as found in vivo, vs, a single isoform, we have compared t he biological activity of kidney laminins to that of pure laminin 1. The ki dney laminin preparation contained laminin 1 and further isoforms. Both sub strates induced adhesion of a large spectrum of cell types, with kidney lam inins being the most active. Unfolding of the coil-coiled conformation of t he kidney isoforms negatively affected cell adhesion-promoting activity, wh ich indicated that conformation-dependent cell binding is a characteristic feature of many or all laminins. Cellular interactions with kidney laminins were mediated by alpha 3 beta 1 and alpha 6 beta 1 integrins, with the con tribution of alpha 3 beta 1 being apparently lower than that of alpha 6 bet a 1 integrins. Immunofluorescence staining of vinculin and integrin subunit s decorated focal adhesions on kidney laminins which differed in morphology from those formed on laminin 1 alone, in spite of the presence of the latt er in the kidney preparation. These observations collectively indicate that tissue specific but often overlapping expression of laminin isoforms might modulate cell behavior by the activation of distinct sets of integrins and by the induction of distinct molecular assemblies within the cell adhesion signaling complexes. (C) 1999 Elsevier Science B.V./International Society of Matrix Biology. All rights reserved.