RKIP Contributes to IFN-γ Synthesis by CD8+ T Cells after Serial TCR Triggering in Systemic Inflammatory Response Syndrome

Abstract

Systemic inflammatory response syndrome (SIRS) is associated with the development of severe medical complications including progression to multiple organ dysfunction syndrome and even death. To date, only marginal improvements in terms of therapeutic options have been established for patients affected by SIRS. Raf kinase inhibitor protein (RKIP) is a regulator of MAPK and NF-κB signaling cascades which are both critical for production of the proinflammatory cytokines responsible for SIRS initiation. By testing a T cell dependent mouse model of SIRS which utilizes staphylococcal enterotoxin A (SEA) specific for Vβ3+ T cells, we show that RKIP is necessary for the exaggerated production of IFNγ from SIRS splenocytes. This effect was not due to differences in T cell expansion, IL-10 production, or APC priming, but rather a cell intrinsic defect lying downstream of the T cell receptor in SEA-specific CD8+ T cells. Importantly, mice lacking RKIP were still able to proliferate, survive, and contribute to cytokine production in response to PAMP-TLR mediated stimuli, despite the TCR-dependent defects seen in our SIRS model. Finally, by blocking RKIP in wild type SIRS splenocytes, the IFNγ response by CD8+ Vβ3+ T cells was significantly diminished. These data suggest that RKIP may be a potential therapeutic target in SIRS by curbing effector cytokine production from CD8+ T cells during serial TCR triggering.

Interactions of RKIP with Inflammatory Signaling Pathways

“…In this model, RKIP contributed to exaggerated production of IFN-γ from stimulated splenocytes, with suggestion that RKIP expression actually drives IFN-γ production. 30 In further support of this, the IFN-γ response in SIRS was significantly diminished using a small molecule inhibitor of RKIP (locostatin) to block RKIP in wild-type splenocytes. Locostatin alkylates a conserved histidine residue (His86) within the RKIP ligand-binding pocket, 31 preventing RKIP from binding to its ligands and inhibiting RKIP functions.…”

“…SIRS results from the general release of large quantities of pro-inflammatory cytokines including IL-6, TNF-α and interferon-γ (IFN-γ). 30 This cytokine storm can lead to an overwhelming clinical collapse. In this model, RKIP contributed to exaggerated production of IFN-γ from stimulated splenocytes, with suggestion that RKIP expression actually drives IFN-γ production.…”

“…The inhibitory effect of locostatin on RKIP associated with a decrease in IFN-γ suggested that RKIP binding pocket inhibitors may be therapeutic targets in certain diseases. 30 However, much remains to be understood regarding the mechanism for these effects, including the impact of locostatin on the NF-κB and ERK/MAPK pathways.…”

Responses to LPS boost effector CD8 T-cell accumulation outside of signals 1 and 2

“…Staining and flow cytometry As previously described, 34 ,1 3 10 6 cells were collected and suspended in 100 mL of staining buffer (BSS buffer with 3% fetal bovine serum, 0.1% sodium azide) for surface staining. To block nonspecific binding cells were incubated on ice for 10 min with Fc blocking solution containing (mouse serum (Sigma), human IgG (Sigma), and the anti-mouse Fc mAb 2.4G2 35 ), then on ice for 30 min with fluorescently conjugated monoclonal antibodies (mAbs).…”

RKIP Structure Drives Its Function: A Three-State Model for Regulation of RKIP

“…1–3 As expected for a protein involved in so many pathways, modulating RKIP function results in a wide range of physiological effects. Depletion or inactivation of RKIP results in disruption of normal cellular stasis and can lead to chromosomal abnormalities, 4 metastatic cancer, 5–7 asthma, 8 systemic inflammatory response syndrome, 9 Alzheimer’s, 10 and heart disease. 2 Disruption of RKIP function has even been implicated as a colonization strategy for the bacteria Helicobacter pylori , resulting in apoptosis in gastric epithelial cells.…”