Integrin heterodimer and receptor complexity in avian and mammalian cells

Abstract

We report data showing that the integrin receptor complex in chickens contains several discrete heterodimers all sharing the β1-integrin subunit combined separately with different α-subunits. Using antisera to synthetic peptides based on cDNA sequences of chicken and human α-integrin subunits to analyze the integrin complement of avian and mammalian cells, we show that band 2 of the chicken integrin complex contains α-subunits related to both α3- and α5-subunits of human integrins. α3β1 and α5β1 have both previously been shown in human cells to be fibronectin receptors and α3β1 can also act as a receptor for laminin and collagen. We also provide evidence for the presence, in band 1 of the chicken integrin complex, of a third integrin α-subunit which is also α5 related. This integrin subunit exists in a separate heterodimer complex with β1 and binds to fibronectin-affinity columns. These results provide explanations for published data showing that the avian integrin complex contains receptor activity for a variety of extracellular matrix proteins. We conclude that the chicken integrin complex comprises a set of β1-integrin heterodimers equivalent to the human VLA antigens and includes at least two fibronectin receptors. Finally, we show that chicken embryo fibroblasts also contain a β3-class integrin related to the RGD receptors defined in various human cells.