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Updated: Aug 26, 2026
Peptide-based Identification of Functional Motifs and their Binding Partners
Published on: June 30, 2013
Extracellular Nef protein targets CD4+ T cells for apoptosis by interacting with CXCR4 surface receptors
Cleve O James1, Ming-Bo Huang, Mafuz Khan
1Department of Microbiology/Immunology/Biochemistry. Cardiovascular Research Institute, Morehouse School of Medicine, Atlanta, Georgia, USA.
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.
Insights
Soluble Nef protein induces apoptosis in CD4(+) T cells via the CXCR4 receptor. This finding suggests a mechanism contributing to CD4(+) T cell depletion in HIV-1 infection and AIDS progression.
Area of Science:
- Immunology
- Virology
- Cell Biology
Background:
- The human immunodeficiency virus type 1 (HIV-1) Nef protein is known to play a critical role in viral pathogenesis.
- Soluble Nef protein's impact on CD4(+) T cells, crucial components of the immune system, remains an area of active investigation.
Purpose of the Study:
- To investigate the effects of soluble Nef protein on CD4(+) T cell apoptosis.
- To identify the cellular receptor and pathways involved in Nef-induced CD4(+) T cell death.
Main Methods:
- CD4(+) T-cell cultures were exposed to soluble Nef protein.
- Apoptosis was assessed using terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL) and analysis of apoptotic hallmarks.
- Involvement of protein kinases, Nef/anti-Nef antibody complexes, and specific cellular receptors (CXCR4, CCR5, CD4) were examined through blocking experiments and cell line transfections.
Main Results:
- Soluble Nef protein induced dose- and time-dependent apoptosis in CD4(+) T cells, evidenced by DNA laddering and caspase 3 activation.
- Nef-induced apoptosis was inhibited by protein kinase inhibitors and anti-Nef antibodies.
- CXCR4 was identified as the cellular receptor mediating Nef-induced apoptosis, as demonstrated by antibody/ligand blocking and experiments with CXCR4-deficient and -transfected cell lines.
Conclusions:
- Extracellular soluble Nef protein directly induces apoptosis in CD4(+) T cells.
- The CXCR4 receptor and protein kinases are implicated in the Nef-mediated apoptotic pathway.
- These findings suggest a potential mechanism for CD4(+) T cell depletion in HIV-1 infection, contributing to AIDS pathogenesis.
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