Department of Signal Transduction, Institute of Molecular Genetics of the Czech Academy of Sciences, Prague, Czechia.
Research Unit for Rare Diseases, Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University and General University Hospital in Prague, Prague, Czechia.
Front Immunol. 2021 Feb 11;11:591975. doi: 10.3389/fimmu.2020.591975. eCollection 2020.
The systemic anaphylactic reaction is a life-threatening allergic response initiated by activated mast cells. Sphingolipids are an essential player in the development and attenuation of this response. synthesis of sphingolipids in mammalian cells is inhibited by the family of three ORMDL proteins (ORMDL1, 2, and 3). However, the cell and tissue-specific functions of ORMDL proteins in mast cell signaling are poorly understood. This study aimed to determine cross-talk of ORMDL2 and ORMDL3 proteins in IgE-mediated responses. To this end, we prepared mice with whole-body knockout (KO) of and/or genes and studied their role in mast cell-dependent activation events and . We found that the absence of ORMDL3 in bone marrow-derived mast cells (BMMCs) increased the levels of cellular sphingolipids. Such an increase was further raised by simultaneous ORMDL2 deficiency, which alone had no effect on sphingolipid levels. Cells with double ORMDL2 and ORMDL3 KO exhibited increased intracellular levels of sphingosine-1-phosphate (S1P). Furthermore, we found that concurrent ORMDL2 and ORMDL3 deficiency increased IκB-α phosphorylation, degranulation, and production of IL-4, IL-6, and TNF-α cytokines in antigen-activated mast cells. Interestingly, the chemotaxis towards antigen was increased in all mutant cell types analyzed. Experiments showed that passive cutaneous anaphylaxis (PCA), which is initiated by mast cell activation, was increased only in ORMDL2,3 double KO mice, supporting our observations with mast cells. On the other hand, ORMDL3 KO and ORMDL2,3 double KO mice showed faster recovery from passive systemic anaphylaxis, which could be mediated by increased levels of blood S1P presented in such mice. Our findings demonstrate that deficiency potentiates the ORMDL3-dependent changes in mast cell signaling.
全身性过敏反应是一种由激活的肥大细胞引发的危及生命的过敏反应。鞘脂是这种反应发展和减弱的重要参与者。哺乳动物细胞中鞘脂的合成受到 ORMDL 蛋白家族（ORMDL1、2 和 3）的抑制。然而，ORMDL 蛋白在肥大细胞信号转导中的细胞和组织特异性功能知之甚少。本研究旨在确定 ORMDL2 和 ORMDL3 蛋白在 IgE 介导的反应中的串扰。为此，我们制备了全身敲除（KO）和/或基因的小鼠，并研究了它们在肥大细胞依赖性激活事件中的作用和。我们发现，骨髓来源的肥大细胞（BMMCs）中 ORMDL3 的缺失增加了细胞内鞘脂的水平。这种增加进一步因同时缺乏 ORMDL2 而升高，而 ORMDL2 单独对鞘脂水平没有影响。具有双重 ORMDL2 和 ORMDL3 KO 的细胞表现出增加的细胞内鞘氨醇-1-磷酸（S1P）水平。此外，我们发现，同时缺乏 ORMDL2 和 ORMDL3 增加了抗原激活的肥大细胞中 IκB-α 磷酸化、脱颗粒和白细胞介素-4（IL-4）、白细胞介素-6（IL-6）和肿瘤坏死因子-α（TNF-α）细胞因子的产生。有趣的是，在所有分析的突变细胞类型中，抗原趋化性都增加了。实验表明，由肥大细胞激活引发的被动皮肤过敏反应（PCA）仅在 ORMDL2,3 双 KO 小鼠中增加，这支持了我们对肥大细胞的观察。另一方面，ORMDL3 KO 和 ORMDL2,3 双 KO 小鼠从被动全身性过敏反应中更快地恢复，这可能是由这些小鼠血液中 S1P 水平升高介导的。我们的研究结果表明，缺乏增强了 ORMDL3 依赖性肥大细胞信号转导的变化。
