Expression and regulation of the 67-kda laminin-binding protein and its precursor gene in lymphoid-cells.

The 67-kDa laminin-binding protein is a non-integrin laminin-binding protein that mediates cancer cell adhesion and migration. The expression of the 67-kDa laminin-binding protein and of its putative precursor, a 37-kDa polypeptide, was studied in peripheral T-cells and T-lymphoma cell lines. Immunofluorescence experiments detected antigen in both the cytosol and on the cell membrane. On immunoblots of T-cell protein extracts, both the 37-kDa precursor and the mature 67-kDa protein were present. The mRNA for the precursor was expressed in both immature and mature thymocytes. In three independent T-lymphoma cell lines, the mRNA levels were decreased after prolonged stimulation with phorbol esters. Since the latter directly activate protein kinase C, it appears that regulation of the 37-kDa precursor in T-cells may be mediated by the signal transduction cascade associated with protein kinase C activation.