Péterfy Hajna, Tóth Gábor, Pecht Israel, Erdei Anna
Department of Immunology, Eötvös Loránd University, Pázmány Péter sétány 1/C, H-1117 Budapest, Hungary.
Int Immunol. 2008 Oct;20(10):1239-45. doi: 10.1093/intimm/dxn083. Epub 2008 Jul 24.
A peptide with the natural sequence derived from the complement component C3a, designated C3a7, and C3a9, having a modified sequence of that, was previously shown to inhibit the high-affinity IgER (FcepsilonRI)-induced secretory response of both mucosal and serosal-type mast cells. In addition, several processes that couple the FcepsilonRI stimulus to the cellular response were all suppressed in the presence of these peptides. Here, we show that peptide C3a9 binds to the FcepsilonRI on the surface of unperturbed mast cells (rat mucosal-type RBL-2H3 cell line) and remains bound even after FcepsilonRI-IgE aggregation by antigen as assessed by confocal microscopy. Moreover, that peptide interferes the initial steps of FcepsilonRI-coupling network. Namely, peptide binding to the FcepsilonRI beta-chain interrupts this chain's association with both src family protein tyrosine kinases Lyn and Fyn and enhances the internalization of the receptor. C3a9 was further found to inhibit the phosphorylation of two members of the mitogen-activated protein kinase family, extracellular signal-regulated kinase (ERK) and p38. Although ERK is usually activated via the ras-raf-mitogen-activated protein kinase/ERK kinase (MEK) pathway, our results show that C3a9 has no effect on the c-raf phosphorylation, suggesting that this complement-derived peptide inhibits ERK activation via an alternative route. C3a9 also inhibits the late-phase response to FcepsilonRI stimulus of bone marrow-derived mast cells, reducing secretion of the inflammatory cytokines IL-6 and tumor necrosis factor-alpha. Taken together, the consequence of its interference with the earliest steps of FcepsilonRI stimulus-response coupling and the C3a-derived peptide inhibits both the immediate and the late-phase responses of mast cells.
一种具有源自补体成分C3a的天然序列的肽，命名为C3a7和C3a9，其具有修饰后的序列，先前已证明可抑制高亲和力IgER（FcepsilonRI）诱导的黏膜型和浆膜型肥大细胞的分泌反应。此外，在这些肽存在的情况下，将FcepsilonRI刺激与细胞反应偶联的几个过程均受到抑制。在此，我们表明肽C3a9与未受干扰的肥大细胞（大鼠黏膜型RBL-2H3细胞系）表面的FcepsilonRI结合，并且通过共聚焦显微镜评估，即使在抗原使FcepsilonRI-IgE聚集后仍保持结合。此外，该肽干扰FcepsilonRI偶联网络的初始步骤。也就是说，肽与FcepsilonRIβ链的结合中断了该链与src家族蛋白酪氨酸激酶Lyn和Fyn的缔合，并增强了受体的内化。进一步发现C3a9可抑制丝裂原活化蛋白激酶家族的两个成员，细胞外信号调节激酶（ERK）和p38的磷酸化。尽管ERK通常通过ras-raf-丝裂原活化蛋白激酶/ERK激酶（MEK）途径激活，但我们的结果表明C3a9对c-raf磷酸化没有影响，这表明这种源自补体的肽通过替代途径抑制ERK激活。C3a9还抑制骨髓源性肥大细胞对FcepsilonRI刺激的晚期反应，减少炎性细胞因子IL-6和肿瘤坏死因子-α的分泌。综上所述，其对FcepsilonRI刺激-反应偶联最早步骤的干扰结果表明，源自C3a的肽可抑制肥大细胞的即时和晚期反应。
