Proteomic exploitation on prothymosin α-induced mononuclear cell activation

Prothymosin alpha (ProTa) is an acidic polypeptide associated both with cell proliferation and immune regulation. Although ProTa's immunomodulating activity is well established at cellular level, limited information is available regarding the signaling pathways triggered by ProTα Using 2-DE proteomic technology, we investigated changes in protein expression of ProTa-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 over-expressed upon ProTa activation. Based on the physiological role of upregulated proteins, we propose the following model for ProTa's immunological mode of action: on day 1, ProTa 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, ProTa-activated PBMC express proteins related to adhesion and cytotoxic effector functions, both contributing to the increase of their lytic activity.