Gatekeeper role of 14-3-3τ protein in HIV-1 gp120-mediated apoptosis of human endothelial cells by inactivation of Bad

Objective: HIV-1-associated dementia (HAD) is a major neurological complication often observed in the advanced stages of AIDS. We have reported that 14-3-3 proteins in cerebrospinal fluid, reflecting neuronal cell destruction, is a real-time marker of HAD progression. This study was designed to examine the role of 14-3-3 proteins in HAD. Design: An in-vitro human umbilical vein endothelial cells (HUVEC) model of gp120 protein-induced apoptosis to study the protective role of 14-3-3 in HIV-1 gp120/ CXCR4-mediated cell death. Methods: The alpha-chemokine receptor-mediated cell death by HIV-1 envelope protein, gp120, the critical event that causes neuron loss and endothelial cell injury, was evaluated in HUVEC undergoing gp120-induced apoptosis through the CXCR4 receptor. We studied the effects of siRNA for each 14-3-3 isoform on the death of HUVEC treated with CXCR4-preferring gp120 (IIIB). Results: Gp120 increased the expression of 14-3-3 tau in HUVEC. The binding of Gp120 to CXCR4 induced apoptosis of HUVEC through decreased binding of 14-3-3 tau to the pro-apoptotic molecule, Bad. Treatment of the cells with dsRNA against 14-3-3 tau enhanced the gp120-mediated dephosphorylation of Bad and its association with Bcl-XL in mitochondria, accelerating the gp120-induced apoptosis, whereas suppression of Bad by RNAi rescued the cells from apoptosis triggered by gp120. Conclusions: The specific up-regulation of 14-3-3 tau in HUVEC negatively regulated gp120/CXCR4-mediated cell death by protecting Bad dephosphorylation. 2007 Lippincott Williams & Wilkins.