HIV-1 gp120 receptor on CD4-negative brain cells activates a tyrosine kinase

Human immunodeficiency virus (HIV-1) infection in the human brain leads to characteristic neuropathological changes, which may result indirectly from interactions of the envelope glycoprotein gp120 with neurons and/or glial cells. We therefore investigated the binding of recombinant gp120 (rgp120) to human neural cells and its effect on intracellular signalling. Here we present evidence that rgp120, besides binding to galactocerebroside or galactosyl-sulfatide, specifically binds to a protein receptor of a relative molecular mass of approximately 180,000 Da (180 kDa) present on the CD4-negative glioma cells D-54, but not on Molt4 T lymphocytes. Binding of rgp120 to this receptor rapidly induced a tyrosine-specific protein kinase activity leading to tyrosine phosphorylation of 130- and 115-kDa proteins. The concentration of intracellular calcium was not affected by rgp120 in these cells. Our data suggest a novel signal transducing HIV-1 gp120 receptor on CD4-negative glial cells, which may contribute to the neuropathological changes observed in HIV-1-infected brains.