Nef is physically recruited into the immunological synapse and potentiates T cell activation early after TCR engagement

J Immunol. 2005 Nov 1;175(9):6050-7. doi: 10.4049/jimmunol.175.9.6050.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • CD28 Antigens / physiology
  • Calcium Signaling
  • Gene Products, nef / chemistry
  • Gene Products, nef / physiology*
  • HIV / physiology*
  • Humans
  • Jurkat Cells
  • Lymphocyte Activation*
  • Membrane Microdomains / metabolism*
  • NF-kappa B / metabolism
  • NFATC Transcription Factors / metabolism
  • Protein Kinase C / physiology
  • Protein Structure, Tertiary
  • Protein-Serine-Threonine Kinases / physiology
  • Receptors, Antigen, T-Cell / physiology*
  • T-Lymphocytes / immunology*
  • nef Gene Products, Human Immunodeficiency Virus
  • p21-Activated Kinases

Substances

  • CD28 Antigens
  • Gene Products, nef
  • NF-kappa B
  • NFATC Transcription Factors
  • Receptors, Antigen, T-Cell
  • nef Gene Products, Human Immunodeficiency Virus
  • PAK2 protein, human
  • Protein-Serine-Threonine Kinases
  • p21-Activated Kinases
  • Protein Kinase C