Human immunodeficiency virus type-1 envelope glycoprotein (gp120(env)) binding to cell surface CD4 receptor triggers a broad range of intracellular effects leading to T cell activation and cell cycle entry. Among these effects we and others previously reported on the nuclear translocation of the nuclear factor-kappaB (NF-kappaB) transcription factor. The present work further investigates the signal transduction pathways involved in gp120(env)-induced NF-kappaB activation. We demonstrate that gp120(env)-CD4 interaction stimulates the hyperphosphorylation of IkappaB-alpha inhibitory protein. Conversely, overexpression of a dominant-negative IkappaB-alpha transgene mutated at S32 and S36 residues, abolishes gp120(env)-induced NF-kappaB activation. IkappaB kinases (IKKs) activity was found to be selectively enhanced following CD4 engagement with gp120(env) and to mediate the phosphorylation of IkappaB-alpha while co-transfection experiments using dominant-negative forms of IKKs inhibited gp120(env)-induced NF-kappaB activation. Taken together, these results confirm that IKKs complex play a key role in gp120(env)-induced NF-kappaB activation.