Extracellular Nef protein targets CD4+ T cells for apoptosis by interacting with CXCR4 surface receptors.

Authors:
James CO, Huang MB, Khan M, Garcia-Barrio M, Powell MD, Bond VC
In:
Source: J Virol
Publication Date: (2004)
Issue: 78(6): 3099-109
Research Area:
Immunotherapy / Hematology
Basic Research
Cells used in publication:
293
Species: human
Tissue Origin: kidney
Jurkat
Species: human
Tissue Origin: blood
MDA-MB-468
Species: human
Tissue Origin: breast
MDA-MB-231
Species: human
Tissue Origin: breast
H9
Species: human
Tissue Origin: blood
Mononuclear, peripheral blood, human
Species: human
Tissue Origin: blood
Abstract
The effects of soluble Nef protein on CD4(+) T cells were examined. CD4(+)-T-cell cultures exposed to soluble Nef were analyzed for apoptosis by terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling and hallmarks of apoptosis including cytoplasmic shrinkage, nuclear fragmentation, DNA laddering, and caspase activation. We observed dose- and time-dependent inductions of apoptosis. DNA laddering and activated caspase 3 were also evident. Cells treated with Nef/protein kinase inhibitor complexes were protected from Nef-induced apoptosis, suggesting possible roles for protein kinases in the apoptosis pathway. Similarly, cells treated with Nef/anti-Nef antibody complexes were protected from Nef-induced apoptosis. The cellular receptor responsible for Nef-induced apoptosis was identified through antibody- and ligand-blocking experiments as a receptor commonly involved in viral entry. CXCR4 antibodies, as well as the endogenous ligand SDF-1alpha, were effective in blocking Nef-induced apoptosis, while CCR5 and CD4 antibodies were ineffective. Moreover, a CXCR4-deficient cell line, MDA-MB-468, which was resistant to Nef-induced apoptosis, became sensitive upon transfection with a CXCR4-expressing vector. This study suggests that extracellular Nef protein could contribute to the decline of CD4 counts prior to and during the onset of AIDS in patients with human immunodeficiency virus type 1 infections.