Comparative functional role of PC7 and furin in the processing of the HIV envelope glycoprotein gp160

The intracellular proteolytic processing of HIV envelope glycoprotein gp160 into gp120/gp41 is an essential step for virus infectivity, Several convertases, belonging to the proprotein convertase family, have been proposed as candidate gp160 processing enzymes, Here we demonstrate using RT-PCR that resting human T4 lymphocytes weakly express PC7, furin, and PC5 mRNA whereas lymphocytes activated under conditions favoring HIV replication express 5-10-fold higher levels of furin and PC7. In this report, we examined the capability of the newly cloned convertase PC7 to cleave gp160 into gp120/gp41 and compared it to furin, This was carried out in a cell-based assay whereby both gp160 and the cognate convertase were coexpressed in the constitutively secreting BSC40 cells and in the regulated AtT20 cells, as well as using two in vitro assays which examined the cleavage of gp160 or of a synthetic peptide spanning the cleavage site, The data demonstrate that PC7 can cleave specifically and in a cell-type specific manner gp160 into gp120/gp41, suggesting that both furin and PC7 are so far the major PC-like candidate gp160 convertase in T4 lymphocytes. (C) 1997 Federation of European Biochemical Societies.