We have previously characterized the biogenesis of the human CD8α protein expressed in rat epithelial cells. We now describe the biosynthesis, post-translational maturation and hetero-oligomeric assembly of the human CD8α/p56 lck protein complex in stable transfectants obtained from the same cell line. There were no differences in the myristilation of p56 lck , or in the dimerization, O-glycosylation and transport to the plasma membrane of CD8α, between cells expressing either one or both proteins. In the doubly expressing cells, dimeric forms of CD8α established hetero-oligomeric complexes with p56 lck , as revealed by co-immunoprecipitation assays performed with anti-CD8α antibody. Moreover, p56 lck bound in these hetero-oligomeric complexes was endowed with auto- and hetero-phosphorylating activity. The present study shows that: (1) the newly synthesized p56 lck binds rapidly to CD8α and most of the p56 lck is bound to CD8α at steady state; (2) CD8α/p56 lck protein complexes are formed at internal membranes as well as at the plasma membrane; and (3) about 50% of complexed p56 lck reaches the cell surface.
