EFFECT OF INHIBITORS OF THE INTRACELLULAR EXOCYTIC PATHWAY ON GLYCOPROTEIN PROCESSING AND MATURATION OF JUNIN VIRUS

The effect of glycoprotein processing and transport on Junin virus (JV ) maturation was studied by using brefeldin A (BFA) and carbonyl cyani de m-chlorophenylhydrazone (CCCP), two inhibitors affecting different steps of the intracellular exocytic pathway, combined with low tempera ture incubation. Both compounds inhibited the multiplication of JV, st rain IV4454, in Vero cells in a dose dependent manner. The addition of the compounds after several cycles of infection for a very short trea tment period produced an immediate arrest on the formation of JV infec tious particles, due to their effect on a late event in JV infective c ycle. Extracellular and cell-associated virus yields were reduced to t he same extent, suggesting that the assembly of virus particles was th e blocked stage. In infected cells treated with CCCP and BFA an altere d subcellular distribution of partially processed viral glycoproteins was observed, with an accumulation of JV glycoproteins at the endoplas mic reticulum and a blockade of their transport to the site of envelop ment in the plasma membrane. Concomitantly, the cleavage of the precur sor GPC to the mature glycoprotein GP38 was strongly inhibited when th e exocytic pathway was affected. Thus, results obtained with BFA allow to conclude that the proteolytic processing of GPC probably occurs at the trans-Golgi network and this cleavage together with the glycoprot ein presence at the cell surface is required for maturation of infecti ous JV particles.