EVIDENCE FOR CELL-SURFACE ASSOCIATION BETWEEN FUSIN AND THE CD4-GP120COMPLEX IN HUMAN CELL-LINES

Accessory cell-surface molecules involved in the entry of human immuno deficiency virus-type 1 into cells have recently been identified and s hown to belong to the family of chemokine receptors, Treatment of huma n cell lines with soluble monomeric gp120 at 37 degrees C induced an a ssociation between the surface CD4-gp120 complex and a 45-kilodalton p rotein, which can be down-modulated by the phorbol ester phorbol 12-my ristate 13-acetate. The three proteins were coprecipitated from the ce ll membranes with antibodies to CD4 or to gp120, The 45-kilodalton pro tein comigrated with fusin on sodium dodecyl sulfate gels and reacted with rabbit antisera to fusin in protein immunoblots, No 45-kilodalton protein could be coprecipitated from similarly treated nonhuman cells , However, infection of 3T3.CD4.401 cells with vaccinia-fusin recombin ant virus (vCBYF1), followed by gp120 treatment, resulted in coprecipi tation of fusin and CD4.401 molecules from their membranes. Together t hese data provide evidence for physical association between fusin and the CD4-gp120 complex on cell membranes.