A full-length cDNA coding for the murine α4 integrin subunit (α4m) was transfected into CHO-K1 cells and cell lines that expressed VLA-4 at their surface as a result of the association of transfected α4m with endogenous hamster β1 were selected. Functionality of the expressed α4mβ1 was shown by adhesion assays on VCAM-1 and antibody (anti-VCAM- 1) inhibition. Pulse chase experiments indicated that transfection of the murine α4 cDNA into CHO cells led to an increase in maturation and a decrease in degradation of the β1 precursor subunit compared to control CHO-K1 cells. This was supported by FACS analysis, using an anti-hamster β1 monoclonal antibody, which showed that more β1 subunit was expressed at the surface of these stably transfected α4m expressing cells. These results support the hypothesis that degradation of precursor β1 is at least partly determined by the quantity of α subunits available intracellulary for heterodimer formation.
