Prothymosin-α Variants Elicit Anti-HIV-1 Response via TLR4 Dependent and Independent Pathways

PLoS One. 2016 Jun 16;11(6):e0156486. doi: 10.1371/journal.pone.0156486. eCollection 2016.

Abstract

Background: Prothymosin α (ProTα) (isoform 2: iso2) is a widely distributed, small acidic protein with intracellular and extracellular-associated functions. Recently, we identified two new ProTα variants with potent anti-HIV activity from CD8+ T cells and cervicovaginal lavage. The first is a splice variant of the ProTα gene known as isoB and the second is the product of ProTα pseudogene 7 (p7). Similarly to iso2, the anti-HIV activity of both variants is mediated by type I IFN. Here we tested whether the immunomodulatory activity of isoB and p7 are also TLR4 dependent and determined their kinetic of release in response to HIV-1 infection.

Methods: Type I, type III, TNF-α and IL-6 mRNA inducing activity was determined in macrophages from wild type and TLR4 knockout mice treated with recombinant ProTα variants. Supernatants from mock and HIV infected cells were analyzed by mass spectrometry in positive and negative modes for the presence of ProTα variants. In silico structural and functional analysis of ProTα variants were performed.

Results: We show that both isoB and p7 upregulate IFN-β, IFN-λ1, IL-6, TNF-α and RANTES mRNAs in primary human macrophages. The potent stimulation of IFN-β by the recombinant ProTα variants in human macrophages is dependent on the TLR4 pathway, whereas the induction of TNF-α and IL-6 may also occur independently of TLR4, suggesting the interaction of ProTα variants with other signaling molecules/receptors. In silico analyses confirmed that the novel isoB and p7 variants are intrinsically disordered proteins, which lack the NLS and mass spectrometry showed release of ProTα variants within minutes post HIV-1 infection. These features are consistent with the function of ProTα variants as damage associate molecular patterns (DAMPs).

Conclusions: Our findings indicate that ProTα variants strongly inhibit viral replication mainly, but not exclusively, through TLR4 signaling and that they are released within minutes of viral infection suggesting that they may function as DAMPs.

MeSH terms

  • Alarmins / genetics
  • Alarmins / immunology
  • Alarmins / pharmacology*
  • Amino Acid Sequence
  • Animals
  • Chemokine CCL5 / genetics
  • Chemokine CCL5 / immunology
  • Gene Expression Regulation
  • HIV Infections / drug therapy*
  • HIV Infections / genetics
  • HIV Infections / immunology
  • HIV Infections / virology
  • HIV-1 / drug effects*
  • HIV-1 / growth & development
  • HIV-1 / immunology
  • Humans
  • Interferon-beta / genetics
  • Interferon-beta / immunology
  • Interferons
  • Interleukin-6 / genetics
  • Interleukin-6 / immunology
  • Interleukins / genetics
  • Interleukins / immunology
  • Intrinsically Disordered Proteins / genetics
  • Intrinsically Disordered Proteins / immunology
  • Intrinsically Disordered Proteins / pharmacology*
  • Macrophages / drug effects
  • Macrophages / immunology
  • Macrophages / virology
  • Mice
  • Mice, Knockout
  • Primary Cell Culture
  • Protein Binding
  • Protein Interaction Mapping
  • Protein Isoforms / genetics
  • Protein Isoforms / immunology
  • Protein Isoforms / pharmacology
  • Protein Precursors / genetics
  • Protein Precursors / immunology
  • Protein Precursors / pharmacology*
  • Sequence Alignment
  • Signal Transduction
  • Thymosin / analogs & derivatives*
  • Thymosin / genetics
  • Thymosin / immunology
  • Thymosin / pharmacology
  • Toll-Like Receptor 4 / deficiency
  • Toll-Like Receptor 4 / genetics
  • Toll-Like Receptor 4 / immunology*
  • Tumor Necrosis Factor-alpha / genetics
  • Tumor Necrosis Factor-alpha / immunology

Substances

  • Alarmins
  • CCL5 protein, human
  • Chemokine CCL5
  • IFNL1 protein, human
  • IL6 protein, human
  • Interleukin-6
  • Interleukins
  • Intrinsically Disordered Proteins
  • Protein Isoforms
  • Protein Precursors
  • Tlr4 protein, mouse
  • Toll-Like Receptor 4
  • Tumor Necrosis Factor-alpha
  • prothymosin alpha
  • Thymosin
  • Interferon-beta
  • Interferons

Grant support

This work was supported by grants from the Campbell Foundation, Lehman Brother Foundation, and Dorothy Rodbell Cohen Cancer Research Program (AM). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.