Division of Molecular Cell Immunology and Allergology, Department of Biomedical Sciences, Nihon University School of Medicine, Tokyo, Japan.
Allergy. 2012 Oct;67(10):1241-9. doi: 10.1111/j.1398-9995.2012.02879.x.. Epub 2012 Jul 30.
FcεRIβ reportedly functions as an amplifier of the FcεRIγ-mediated activation signal using a reconstitution system. However, the amplification mechanisms in human mast cells (MCs) are poorly understood. We previously reported the hyperexpression of FcεRIβ of MCs in giant papillae from vernal keratoconjunctivitis patients, compared with that in conjunctivae from nonallergic conjunctivitis patients. Elucidation of the molecular mechanisms of the amplification induced by FcεRIβ should provide new targets for novel therapeutic interventions. The aim is to understand in greater details the function of FcεRIβ in human MC FcεRI expression and signaling.
FcεRIβ and Lyn expression was reduced using a lentiviral shRNA silencing technique. Localization of Lyn and FcεRIβ in cultured MCs was examined by confocal microscopic analysis. Mediators were measured by ELISAs.
The diminution of FcεRIβ significantly downregulated cell surface FcεRI expression and FcεRI-mediated mediator release/production. The downregulation of FcεRI-mediated degranulation was not only due to the decrease in FcεRI expression. The diminution of FcεRIβ inhibited the redistribution of Lyn within the cell membrane following IgE sensitization. The diminution of Lyn in MCs significantly downregulated FcεRI-mediated degranulation. The recombinant cell-penetrating forms of phosphorylated FcεRIβ immunoreceptor tyrosine-based activation motif (ITAM) for intracellular delivery disturbed the interaction between Lyn and phosphorylated endogenous FcεRIβ ITAM, resulted in inhibiting IgE-dependent histamine release from MCs in vitro and from giant papillae specimens ex vivo.
The interaction between Lyn and FcεRIβ is indispensable for FcεRI-mediated human MC activation, and specific inhibition of the interaction may represent a new therapeutic strategy for the treatment of human allergic diseases.
据报道，FcεRIβ在再构建体系中作为 FcεRIγ 介导的激活信号的放大器发挥作用。然而，人肥大细胞（MC）中的放大机制仍知之甚少。我们之前报道过，与非变应性结膜炎患者的结膜相比，春季角结膜炎患者的巨乳头中 MC 的 FcεRIβ表达过度。阐明 FcεRIβ诱导的放大的分子机制应该为新的治疗干预提供新的靶点。目的是更详细地了解 FcεRIβ在人 MC FcεRI 表达和信号传导中的功能。
使用慢病毒 shRNA 沉默技术降低 FcεRIβ 和 Lyn 的表达。通过共聚焦显微镜分析检查培养的 MC 中 Lyn 和 FcεRIβ 的定位。通过 ELISA 测量介质。
FcεRIβ 的减少显著下调细胞表面 FcεRI 表达和 FcεRI 介导的介质释放/产生。FcεRI 介导的脱颗粒的下调不仅是由于 FcεRI 表达的减少。FcεRIβ 的减少抑制了 IgE 敏化后 Lyn 在细胞膜内的重新分布。MC 中 Lyn 的减少显著下调了 FcεRI 介导的脱颗粒。用于细胞内递送的磷酸化 FcεRIβ 免疫受体酪氨酸基激活基序（ITAM）的重组细胞穿透形式干扰了 Lyn 与磷酸化内源性 FcεRIβ ITAM 之间的相互作用，导致体外从 MC 中和从巨乳头标本中体外抑制 IgE 依赖性组胺释放。
Lyn 和 FcεRIβ 之间的相互作用对于 FcεRI 介导的人 MC 激活是必不可少的，并且相互作用的特异性抑制可能代表治疗人类变应性疾病的新治疗策略。
