Heterologous expression of alpha 1-integrin cDNA generates variable ligand specificities and alterations in cell shape
Abstract
Integrins can mediate a diverse variety of functions that are regulated by unknown mechanisms. Integrin alpha 1 beta 1 can serve as a receptor for laminin-1 and collagen in certain cell types, but is a receptor for only collagen in others. To examine the molecular basis of this difference in specificity, three cell types were transfected with cDNA for the rat alpha 1 subunit. Following transfection with rat alpha 1, pluripotential hematopoietic human K562 cells exhibited alpha 1 beta 1-dependent attachment to collagen IV, but not laminin-1, unless activating antibody TS2/16 was added. The attachment to collagen IV stimulated the elaboration of a spread morphology resembling a differentiated megakarocyte with extensive processes which were absent in response to all other substrates. When MRC-5 cells, a human fibroblastic cell, or RD cells, a human rhabdomyosarcoma line, were transfected with the identical alpha 1-integrin construct, rat alpha 1 beta 1-dependent attachment to both collagen IV and laminin-1 was seen. Therefore differences in ligand specificity can be generated by translation of an identical integrin alpha 1 beta 1 mRNA in different cell types. Despite differences in ligand binding, alpha 1 cDNA-transfected K562 an...Continue Reading
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