Involvement of alpha5beta1 integrins in interleukin 8 production induced by oral viridans streptococcal protein I/IIf in cultured endothelial cells

Abstract

SummaryUsing human endothelial cells, we de®ne a mechanism that accounts for the induction of interleukin 8 (IL-8) by protein I/IIf, an adhesin from Streptococcus mutans serotype f. We report that protein I/IIf interactions with endothelial cells increased the tyrosine phosphorylation of three cellular components with relative mass of 145 000, 125 000 and 70 000 in endothelial cells. These proteins were identi®ed as phospholipase Cg (PLCg), focal adhesion kinase (FAK) and paxillin after immunoprecipitation with monoclonal antibodies (mAbs) and immunoblotting with antiphosphotyrosine mAbs. These results suggested that b1 integrins could be one of the components implicated in the modulin activity of protein I/IIf. By incubating protein I/IIf with either puri®ed a5b1 integrins or with a5b1 integrins overexpressing CHO cells, we demonstrated that a5b1 integrins act as cell receptors for protein I/IIf. We also showed that protein I/IIf interactions with a5b1 integrins lead to IL-8 secretion. Using speci®c inhibitors, we demonstrated that protein I/IIf-induced IL-8 release involves mitogenactivated protein kinases (MAPKs), and that PLCg and PKC also seem to contribute to protein I/IIf stimulation. However, PI-3K activation is not involved in IL-8 release. Altogether, these results indicate that, after binding to a5b1 integrins, protein I/IIf induces IL-8 release by activating the MAPKs signalling pathways.

Cross Talk between MyD88 and Focal Adhesion Kinase Pathways

“…We showed previously that protein I/II, a ligand of integrin ␣ 5 ␤ 1 , induces cytokine production by human endothelial and epithelial cells and FLSs and that this effect is FAK dependent (5,6). In this study, we first verified the capacity of protein I/II to stimulate phosphorylation of FAK in murine bone marrow-derived macrophages.…”

“…B acterial recognition implicates a wide variety of pattern recognition receptors specific for pathogen-associated microbial patterns (PAMPs), 5 including TLRs, lectins, scavenger receptors, and integrins. Among them, TLRs are critical for the development of innate immune responses (1).…”

“…Protein I/II, a cell wall component from oral streptococci, binding to integrin ␣ 5 ␤ 1 induces the production of inflammatory mediators such as IL-6 and IL-8 by human monocytes, epithelial cells, endothelial cells, and fibroblasts (5,6). The signaling events leading to this cytokine release involve FAK, ERK1/2, and JNKs as well as AP-1-binding activity and nuclear translocation of NF-B (6,7).…”

BAFF synthesis by rheumatoid synoviocytes is positively controlled by α5β1 integrin stimulation and is negatively regulated by tumor necrosis factor α and toll‐like receptor ligands

“…FLS express various integrins, and in this study, we also explored the ultimate implication of ␣5␤1 integrin, a well-known receptor of several bacterial PAMPs, in BAFF synthesis (26)(27)(28). Protein I/II, an adhesin derived from viridans streptococci, is an established ␣5␤1 integrin ligand that induces the release of classic proinflammatory cytokines, such as IL-6 and IL-8, by FLS (18). An important result in this study was the finding that protein I/II induced BAFF transcription and secretion by activated FLS.…”

“…A large number of PRRs, such as Toll-like receptor 2 (TLR-2), TLR-4, and TLR-9, as well as numerous integrins are expressed by FLS, and their expression is increased in response to inflammatory stimuli (16,17). We previously showed that LPS, bacterial lipopeptide (BLP), and protein I/II, which are ligands of TLR-4, TLR-2, and ␣5␤1 integrin, respectively, can trigger the release of IL-6 and IL-8 from activated FLS (18,19).…”