Institute for Allergology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, 10117 Berlin, Germany.
Department of Dermatology, The Second Affiliated Hospital, Northwest Hospital, Xi'an Jiaotong University, Xi'an 710004, China.
Cells. 2022 Mar 10;11(6):953. doi: 10.3390/cells11060953.
The recent discovery of MRGPRX2 explains mast cell (MC)-dependent symptoms independently of FcεRI-activation. Because of its novelty, signaling cascades triggered by MRGPRX2 are rudimentarily understood, especially in cutaneous MCs, by which MRGPRX2 is chiefly expressed. Here, MCs purified from human skin were used following preculture or ex vivo and stimulated by FcεRI-aggregation or MRGPRX2 agonists (compound 48/80, Substance P) in the presence/absence of inhibitors. Degranulation was assessed by β-hexosaminidase or histamine release. Phosphorylation events were studied by immunoblotting. As a G protein-coupled receptor, MRGPRX2 signals by activating G proteins; however, their nature has remained controversial. In skin MCs, G and G were required for degranulation, but G was clearly more relevant. Ca++ channels were likewise crucial. Downstream, PI3K was essential for granule discharge initiated by MRGPRX2 or FcεRI. ERK1/2 and JNK were additional participants, especially in the allergic route. Addressing possible points of intersection between early and later events, pERK1/2 and pAKT were found to depend on G, further highlighting its significance. G and Ca++ channels made some contributions to the phosphorylation of ERK. Ca++ differentially affected PI3K activation in FcεRI- vis-à-vis MRGPRX2-signaling, as channel inhibition increased pAKT only when triggered via FcεRI. Collectively, our study significantly extends our understanding of the molecular framework behind granule secretion from skin MCs.
最近发现的 MRGPRX2 独立于 FcεRI 激活解释了肥大细胞（MC）依赖性症状。由于其新颖性，MRGPRX2 触发的信号级联在皮肤 MC 中还处于初步理解阶段，MRGPRX2 主要在皮肤 MC 中表达。在这里，使用了从人皮肤中纯化的 MC，这些 MC 经过预培养或离体培养，并在存在/不存在抑制剂的情况下通过 FcεRI 聚集或 MRGPRX2 激动剂（化合物 48/80、P 物质）进行刺激。脱颗粒通过 β-己糖胺酶或组胺释放来评估。磷酸化事件通过免疫印迹进行研究。作为 G 蛋白偶联受体，MRGPRX2 通过激活 G 蛋白信号；然而，它们的性质一直存在争议。在皮肤 MC 中，G 和 G 对于脱颗粒是必需的，但 G 显然更为重要。Ca++通道同样至关重要。下游，PI3K 对于由 MRGPRX2 或 FcεRI 引发的颗粒释放是必不可少的。ERK1/2 和 JNK 是另外的参与者，特别是在过敏途径中。为了解决早期和晚期事件之间可能的交叉点，发现 pERK1/2 和 pAKT 依赖于 G，进一步强调了 G 的重要性。G 和 Ca++通道对 ERK 的磷酸化有一定的贡献。Ca++ 对 FcεRI-相对于 MRGPRX2 信号的 PI3K 激活有不同的影响，因为只有当通过 FcεRI 触发时，通道抑制才会增加 pAKT。总的来说，我们的研究显著扩展了我们对皮肤 MC 颗粒分泌背后分子框架的理解。
