The fusion domain of HIV gp41 interacts specifically with heparan sulfate on the T-lymphocyte cell surface

Studies of the interaction of the 16 residue fusion peptide domain of human immunodeficiency virus glycoprotein gp41 (gp41(FD)) with T lymphocytes are outlined, Fluorescence measurements of changes in the electrostatic surfac e and dipole potentials of the plasma membrane following the interaction wi th gp41(FD) are described, The results show that gp41(FD) interacts with he paran sulfate located on the cell surface. This interaction is blocked by i nterleukin-8 and abolished by pre-treating the cells with heparitinase. The specificity of the reaction was also assessed by observations that soluble heparan sulfate competes with the cell membrane interaction whereas solubl e heparin (at the levels utilized) does not. Following binding to heparan s ulfate, the interaction with the membrane seems to take place in a cooperat ive manner with the formation of gp41(FD) trimers, In simpler phospholipid membranes, however, a trimeric complex does not appear to be the dominant m ode of interaction, Finally, by repeating some of these studies within an i maging regime, it appears that the gp41(FD)-T-cell interaction takes place within specific domains on the cell surface to similarly localized heparan sulfate moieties.