CD4 engagement by HIV-1 in TF-1 hematopoietic progenitor cells increases protein kinase C activity and reduces intracellular Ca2+ levels.

Starting from our previous observations that the HIV-1-mediated engagement of CD4 induced apoptotic death of TF-1 hematopoietic progenitor cells, in this study we evaluated PKC activity and intracellular Ca2+ levels in TF-1 cells treated with viable and heat-inactivated HIV-1 (strain IIIB) or anti-CD4 Leu3a monoclonal antibody (mAb). Both viable and heat-inactivated HIV-1 or anti-CD4 mAb, but not anti-human cytomegalovirus (HCMV) 66kD protein or anti-CD8 mAb induced a rapid (5-10 min) increase in PKC activity under both serum-containing and serum-free conditions. The same treatment also induced both a transient and a long-lasting (48 hours) decrease (p < 0.05) in intracellular Ca2+ levels in serum-containing cultures. We propose that the observed changes in PKC activity and intracellular Ca2+ levels might be involved in the HIV-1 mediated apoptosis of hematopoietic progenitor cells.