Stable expression of VLA-4 and increased maturation of the beta 1-integrin precursor after transfection of CHO cells with alpha 4m cDNA.

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