Expression of normal and mutant avian integrin subunits in rodent cells [published erratum appears in J Cell Biol 1989 Oct;109(4 Pt 1):1187]

Abstract

We describe the expression of the .beta.1 subunit of avian integrin in rodent cells with the purpose of examining the structure-function relationships of various domains within this subunit. The exogenous subunit is efficiently and stably expressed in 3T3 cells, and it forms hybrid heterodimers with endogenous murine .alpha.-subunits, including .alpha.3 and .alpha.5. These heterodimers are exported to the cell surface and localize in focal contacts where both extracellular matrix and cytoskeleton associate with the plasma membrane. Hybrid heterodimers consisting of exogenous .beta.1 and endogenous .alpha. subunits bind effectively and specifically to columns of cell-binding fragments of fibronectin. The exogenous avian .beta.1 subunit appears to function as well as its endogenous murine equivalent, consistent with the high degree of conservation noted previously for integrins. In contrast, expression of a mutant form of avian integrin .beta.1 subunit lacking the cytoplasmic domain produces hybrid heterodimers which, while efficiently exported to the cell surface and still capable of binding fibronectin, do not localize efficiently in focal contacts. This further implicates the cytoplasmic domain of the .beta.1 subunit in interactions required for cytoskeletal organization.