Proteomic exploitation on prothymosin α‐induced mononuclear cell activation

Abstract

Prothymosin alpha (ProTalpha) is an acidic polypeptide associated both with cell proliferation and immune regulation. Although ProTalpha's immunomodulating activity is well established at cellular level, limited information is available regarding the signaling pathways triggered by ProTalpha. Using 2-DE proteomic technology, we investigated changes in protein expression of ProTalpha-stimulated peripheral blood mononuclear cells (PBMC) in the course of a 3-day incubation. Using healthy donor- and cancer patient-derived PBMC, 12 gels were studied, identifying 53 differing protein spots via PMF comparison analysis. Among others, we identified interleukin-1 receptor-associated kinase 4, heat-shock protein 90, lipocalin 2, ribophorin 1, eukaryotic elongation factor 2, 14-3-3 protein, L-plastin, and MX2 protein, all of which were found to be overexpressed upon ProTalpha activation. Based on the physiological role of upregulated proteins, we propose the following model for ProTalpha's immunological mode of action: on day 1, ProTalpha triggers monocyte activation, possibly via toll-like receptor signaling, and enhances antigen presentation, consequently promoting and stabilizing monocyte-T-cell immune synapse; on day 2, activated monocytes produce interleukin (IL)-1, while T-cell receptor triggering promotes T-cell proliferation and IL-2 production; finally, on day 3, ProTalpha-activated PBMC express proteins related to adhesion and cytotoxic effector functions, both contributing to the increase of their lytic activity.

Prothymosin alpha: a ubiquitous polypeptide with potential use in cancer diagnosis and therapy

“…In the case of proT , these shared properties were further complemented by the recent Wnding that in human macrophages, proT signals via ligating TLR4, the most promiscuous of the TLR, binding also HSP90 and HMBG1 [39]. This data conWrmed our previous observation that proT -stimulated human monocytes upregulated the expression of IRAK4 [85].…”

“…We used proteomics to detect intracellular protein changes induced in mononuclear cells, derived either from normal donors or cancer patients, over the course of a 3-day stimulation with proT [85]. Based on the identiWcation of immunologically signiWcant molecules overexpressed downstream proT activation, we proposed that initially, proT triggers monocyte stimulation via TLR-ligation and signaling and enhances antigen presentation through MHC class II molecule upregulation.…”

Prothymosin-α inhibits HIV-1 via Toll-like receptor 4-mediated type I interferon induction

“…To understand how ProTα mediates its anti-HIV-1 activity, we investigated whether it induced type I IFN production. This question was based on prior work showing that ProTα induces several IFN responsive genes at 24 h after treatment (10,12). In this investigation, we incubated human macrophages with recombinant human ProTα (rProTα; 200 ng/mL) (sequence shown in Fig.…”

“…IRAK4 and IFN responsive genes in peripheral blood mononuclear cells (PBMCs) or MDCs exposed to ProTα (7,12). Other host proteins including the heat shock antigens Hsp60 and Hsp70, or HMGB1 and Tenascin-C expressed during inflammation, stress, and/or necrosis (16)(17)(18), have also been reported to serve as endogenous ligands for TLR4, but binding of these ligands to TLR4 is not associated with the induction of type I IFN.…”

Regional Distribution and Cell Type-Specific Subcellular Localization of Prothymosin Alpha in Brain

“…ProTa, a signal peptide-deficient protein, is associated with cell functions, such as proliferation, division, and survival in various cells (Karapetian et al 2005;Letsas and Frangou-Lazaridis 2006;Jiang et al 2003;Gomez-Marquez 2007;Ueda 2008), and with genomic actions such as binding to linker histone H1, DNA packaging (Papamarcaki and Tsolas 1994;Diaz-Jullien et al 1996;George and Brown 2010), chromatin remodeling (Gomez-Marquez 2007), and regulation of transcription (Martini et al 2000); Karetsou et al 2002). In addition to these intracellular functions, there are also several reports about the immunoregulatory role of extracellular ProTa, such as activation of major histocompatibility complex (MHC) expression (Baxevanis et al 1992), induction of antitumor and antiviral activity (Garbin et al 1997;Mosoian et al 2006), activation of immune cells, and cytokine production (Pineiro et al 2000;Skopeliti et al 2007). There is an interesting report that ProTa induces an immunosuppressive activity against viral infection through the activation of Toll-like receptor-4 (Mosoian et al 2010).…”