Nef Is Physically Recruited into the Immunological Synapse and Potentiates T Cell Activation Early after TCR Engagement

• Published in: Journal of Immunology Vol. 175; no. 9; pp. 6050 - 6057
• Main Authors: Fenard, David, Yonemoto, Wes, de Noronha, Carlos, Cavrois, Marielle, Williams, Samuel A, Greene, Warner C
• Format: Journal Article
• Language: English
• Published: United States Am Assoc Immnol 01.11.2005
• Subjects: Calcium Signaling; CD28 Antigens - physiology; Gene Products, nef - chemistry; Gene Products, nef - physiology; HIV - physiology; Human immunodeficiency virus 1; Humans; Jurkat Cells; Lymphocyte Activation; Membrane Microdomains - metabolism; nef Gene Products, Human Immunodeficiency Virus; NF-kappa B - metabolism; NFATC Transcription Factors - metabolism; p21-Activated Kinases; Protein Kinase C - physiology; Protein Structure, Tertiary; Protein-Serine-Threonine Kinases - physiology; Receptors, Antigen, T-Cell - physiology; T-Lymphocytes - immunology
• ISSN: 0022-1767; 1550-6606; 1365-2567
• DOI: 10.4049/jimmunol.175.9.6050

The HIV-1 protein Nef enhances viral pathogenicity and accelerates disease progression in vivo. Nef potentiates T cell activation by an unknown mechanism, probably by optimizing the intracellular environment for HIV replication. Using a new T cell reporter system, we have found that Nef more than doubles the number of cells expressing the transcription factors NF-kappaB and NFAT after TCR stimulation. This Nef-induced priming of TCR signaling pathways occurred independently of calcium signaling and involved a very proximal step before protein kinase C activation. Engagement of the TCR by MHC-bound Ag triggers the formation of the immunological synapse by recruiting detergent-resistant membrane microdomains, termed lipid rafts. Approximately 5-10% of the total cellular pool of Nef is localized within lipid rafts. Using confocal and real-time microscopy, we found that Nef in lipid rafts was recruited into the immunological synapse within minutes after Ab engagement of the TCR/CD3 and CD28 receptors. This recruitment was dependent on the N-terminal domain of Nef encompassing its myristoylation. Nef did not increase the number of cell surface lipid rafts or immunological synapses. Recently, studies have shown a specific interaction of Nef with an active subpopulation of p21-activated kinase-2 found only in the lipid rafts. Thus, the corecruitment of Nef and key cellular partners (e.g., activated p21-activated kinase-2) into the immunological synapse may underlie the increased frequency of cells expressing transcriptionally active forms of NF-kappaB and NFAT and the resultant changes in T cell activation.