Cystatin B and HIV regulate the STAT-1 signaling circuit in HIV-infected and INF-β-treated human macrophages

J Neurovirol. 2016 Oct;22(5):666-673. doi: 10.1007/s13365-016-0443-6. Epub 2016 May 2.

Abstract

Cystatin B is a cysteine protease inhibitor that induces HIV replication in monocyte-derived macrophages (MDM). This protein interacts with signal transducer and activator of transcription (STAT-1) factor and inhibits the interferon (IFN-β) response in Vero cells by preventing STAT-1 translocation to the nucleus. Cystatin B also decreases the levels of tyrosine-phosphorylated STAT-1 (STAT-1PY). However, the mechanisms of cystatin B regulation on STAT-1 phosphorylation in MDM are unknown. We hypothesized that cystatin B inhibits IFN-β antiviral responses and induces HIV replication in macrophage reservoirs through the inhibition of STAT-1 phosphorylation. Macrophages were transfected with cystatin B siRNA prior to interferon-β treatment or infected with HIV-ADA to determine the effect of cystatin B modulation in STAT-1 localization and activation using immunofluorescence and proximity ligation assays. Cystatin B decreased STAT-1PY and its transportation to the nucleus, while HIV infection retained unphosphorylated STAT (USTAT-1) in the nucleus avoiding its exit to the cytoplasm for eventual phosphorylation. In IFN-β-treated MDM, cystatin B inhibited the nuclear translocation of both, USTAT-1 and STAT-1PY. These results demonstrate that cystatin B interferes with the STAT-1 signaling and IFN-β-antiviral responses perpetuating HIV in macrophage reservoirs.

Keywords: Cystatin B; HIV; IFN-β; Macrophages; STAT-1.

Publication types

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

MeSH terms

  • Cell Nucleus / drug effects
  • Cell Nucleus / immunology
  • Cell Nucleus / virology
  • Cystatin B / antagonists & inhibitors
  • Cystatin B / genetics*
  • Cystatin B / immunology
  • Gene Expression Regulation
  • HIV-1 / growth & development
  • HIV-1 / immunology*
  • Host-Pathogen Interactions*
  • Humans
  • Interferon-beta / pharmacology*
  • Macrophages / drug effects*
  • Macrophages / immunology
  • Macrophages / virology
  • Phosphorylation / drug effects
  • Primary Cell Culture
  • Protein Transport / drug effects
  • RNA, Small Interfering / genetics
  • RNA, Small Interfering / metabolism
  • STAT1 Transcription Factor / genetics*
  • STAT1 Transcription Factor / immunology
  • Signal Transduction
  • Transfection
  • Virus Replication / drug effects

Substances

  • CSTB protein, human
  • RNA, Small Interfering
  • STAT1 Transcription Factor
  • STAT1 protein, human
  • Interferon-beta
  • Cystatin B