Pathophysiological roles of basophils and mast cells in allergic inflammations

高亲和力IgE受体（FcεRI）在肥大细胞和嗜碱性细胞上的作用，通过脱颗粒诱导预先形成的炎症介质的释放，以及炎症细胞因子的重新合成和分泌，导致一系列急性和慢性过敏症状。SLP-76家族的两个接头SLP-76和MIST在肥大细胞和嗜碱性细胞中均有表达，两者均参与FcεRI -信号转导。然而，SLP-76和MIST在这一过程中的功能冗余和/或特异性尚不清楚。在本研究中，我们打算通过使用MIST和/或SLP-76缺乏的小鼠来阐明SLP-76和MIST在fcε ri介导的过敏反应中的功能冗余和/或特异性。与野生型细胞相比，在MIST-和slp -76缺陷肥大细胞中，fcε - ri诱导的脱颗粒分别轻微和深度减少。在slp -76缺陷细胞中检测到的残余脱颗粒被引入mist缺陷完全废除。为了进一步了解SLP-76和MIST在fc - ri信号传导中的功能差异的分子基础，我们研究了这两个接头的分子相互作用模式和膜靶向。SLP-76与grb2相关适配器在She （Gads）下游存在关联，而MIST则没有。然而，当MIST中的grb2结合基序被SLP-76中的高亲和力RXXK sh3结合基序取代时，该突变体（MIST- gbf）获得了与Gads结合的能力。尽管野生型MIST在抗原接触部位的招募和簇形成比SLP-76弱，但在这些fcε ri诱导的变化方面，MIST GBF突变体的表现与SLP-76相似。此外，肥大细胞中表达MIST- gbf可将fcε ri介导的脱颗粒增强到与表达SLP-76的细胞相当的水平，这表明gds结合基序（RXXK）的存在决定了SLP-76在fcε ri介导的肥大细胞活化中比MIST的功能优势。由于SLP-76是组成性的，而MIST在肥大细胞和嗜碱性细胞中诱导表达，这两个SLP-76家族适配器分别在过敏反应中作为fcε ri介导的肥大细胞激活的基础必需调节剂和放大器。少

Engagement of the high-affinity IgE receptor (FcεRI) on mast cells as well as basophils induces the release of preformed inflammatory mediators by degranulation and also the de novo synthesis and secretion of inflammatory cytokines, leading to an array of acute and chronic allergic symptoms. Two SLP-76 family adaptors, SLP-76 and MIST, are expressed in both mast cells and basophils, and both are involved in FcεRI -signaling. However, the functional redundancy and/or specificity of SLP-76 and MIST in this process remain unclear. In the present study, we intended to clarify the functional redundancy and/or specificity of SLP-76 and MIST in FcεRI-mediated allergic reactions by using mice deficient in MIST and/or SLP-76.FcεRI-induced degranulation was slightly and profoundly reduced in MIST- and SLP-76-deficient mast cells than in wild type cells, respectively. The residual degranulation detected in SLP-76-deficient cells was completely abrogated by the introduction of a MIST-deficiency. T … More o gain insight into the molecular basis for the functional difference between SLP-76 and MIST in FcεRI-signaling, we examined the mode of molecular interactions and membrane targeting of these two adaptors. SLP-76 associated with Grb2-related adaptor downstream of She (Gads) whereas MIST did not. However, when the Grb2-binding motif in MIST was replaced with a high-affinity RXXK SH3-binding motif from SLP-76, this mutant (MIST-GBF) gained the ability to associate with Gads. Although recruitment and cluster formation of wild type MIST at the antigen contact site were weaker than that observed for SLP-76, the MIST GBF mutant behaved like SLP-76 in terms of these FcεRI-induced changes. Furthermore, expression of MIST-GBF in mast cells enhanced FcεRI-mediated degranulation to a level comparable to that observed in SLP-76-expressing cells, indicating that the presence of the Gads-binding motif (RXXK) determines the functional dominance of SLP-76 over MIST in FcεRI-mediated mast cell activation.Since SLP-76 is constitutively but MIST is inducibly expressed in mast cells and basophils, these two SLP-76 family adaptors function as a basal essential regulator and an amplifier of FcεRI-mediated mast cell activation, respectively, in allergic reactions. Less