HIV-1 Vpu Downregulates Tim-3 from the Surface of Infected CD4+ T Cells

J Virol. 2020 Mar 17;94(7):e01999-19. doi: 10.1128/JVI.01999-19. Print 2020 Mar 17.

Abstract

Along with other immune checkpoints, T cell immunoglobulin and mucin domain-containing protein 3 (Tim-3) is expressed on exhausted CD4+ and CD8+ T cells and is upregulated on the surface of these cells upon infection by human immunodeficiency virus type 1 (HIV-1). Recent reports have suggested an antiviral role for Tim-3. However, the molecular determinants of HIV-1 which modulate cell surface Tim-3 levels have yet to be determined. Here, we demonstrate that HIV-1 Vpu downregulates Tim-3 from the surface of infected primary CD4+ T cells, thus attenuating HIV-1-induced upregulation of Tim-3. We also provide evidence that the transmembrane domain of Vpu is required for Tim-3 downregulation. Using immunofluorescence microscopy, we determined that Vpu is in close proximity to Tim-3 and alters its subcellular localization by directing it to Rab 5-positive (Rab 5+) vesicles and targeting it for sequestration within the trans- Golgi network (TGN). Intriguingly, Tim-3 knockdown and Tim-3 blockade increased HIV-1 replication in primary CD4+ T cells, thereby suggesting that Tim-3 expression might represent a natural immune mechanism limiting viral spread.IMPORTANCE HIV infection modulates the surface expression of Tim-3, but the molecular determinants remain poorly understood. Here, we show that HIV-1 Vpu downregulates Tim-3 from the surface of infected primary CD4+ T cells through its transmembrane domain and alters its subcellular localization. Tim-3 blockade increases HIV-1 replication, suggesting a potential negative role of this protein in viral spread that is counteracted by Vpu.

Keywords: HIV; Tim-3; Vpu; membrane trafficking; viral release.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • CD4-Positive T-Lymphocytes / virology*
  • Cell Membrane / metabolism
  • Down-Regulation*
  • Gene Expression Regulation
  • HEK293 Cells
  • HIV-1 / metabolism
  • HeLa Cells
  • Hepatitis A Virus Cellular Receptor 2 / metabolism*
  • Human Immunodeficiency Virus Proteins / metabolism*
  • Humans
  • Interferon-beta / metabolism
  • RNA, Small Interfering / metabolism
  • Viral Regulatory and Accessory Proteins / metabolism*
  • trans-Golgi Network / metabolism

Substances

  • HAVCR2 protein, human
  • Hepatitis A Virus Cellular Receptor 2
  • Human Immunodeficiency Virus Proteins
  • RNA, Small Interfering
  • Viral Regulatory and Accessory Proteins
  • vpu protein, Human immunodeficiency virus 1
  • Interferon-beta