Laboratory of Molecular Immunogenetics, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
J Immunol. 2013 Mar 1;190(5):2058-67. doi: 10.4049/jimmunol.1201503. Epub 2013 Jan 28.
FcεRI engagement in mast cells (MCs) induces the activation of two distinct sphingosine kinase isoforms (SphK1 and SphK2) to produce sphingosine-1-phosphate, a mediator essential for MC responses. Whereas embryonic-derived SphK2-null MCs showed impaired responses to Ag, RNA silencing studies on other MC types indicated a dominant role for SphK1. Given the known functional heterogeneity of MCs, we explored whether the reported differences in SphK1 or SphK2 usage could be reflective of phenotypic differences between MC populations. Using lentiviral-based short hairpin RNA to silence SphK1 or SphK2, we found that SphK2 is required for murine MC degranulation, calcium mobilization, and cytokine and leukotriene production, irrespective of the tissue from which the MC progenitors were derived, the stage of MC granule maturity, or the conditions used for differentiation. This finding was consistent with the lack of a full allergic response in SphK2-null mice challenged to undergo passive cutaneous anaphylaxis. A redundant role for both SphKs was uncovered, however, in chemotaxis toward Ag in all MC types tested and in TNF-α production in certain MC types. In contrast, human MC responses were dependent only on SphK1, associating with a more robust expression of this isoform and a more varied representation of SphK variants relative to murine MCs. The findings show that the function of SphK1 and SphK2 can be interchangeable in MCs; however, an important determinant of SphK isoform usage is the species of origin and an influencing factor, the tissue from which MCs may be derived and/or their differentiation state.
FcεRI 与肥大细胞 (MCs) 的结合会诱导两种不同的鞘氨醇激酶同工型 (SphK1 和 SphK2) 的激活，从而产生对 MC 反应至关重要的介质——鞘氨醇-1-磷酸。虽然胚胎衍生的 SphK2 缺失型 MCs 对 Ag 的反应受损，但对其他 MC 类型的 RNA 沉默研究表明 SphK1 起主导作用。鉴于 MC 已知的功能异质性，我们探讨了报道的 SphK1 或 SphK2 用途的差异是否反映了 MC 群体之间表型的差异。我们使用基于慢病毒的短发夹 RNA 沉默 SphK1 或 SphK2，发现 SphK2 是鼠类 MC 脱颗粒、钙动员以及细胞因子和白三烯产生所必需的，无论 MC 祖细胞来源于何种组织、MC 颗粒成熟的阶段或分化使用的条件如何。这一发现与在接受被动皮肤过敏反应挑战的 SphK2 缺失型小鼠中缺乏完整的过敏反应一致。然而，我们发现两种 SphK 在所有测试的 MC 类型中对 Ag 的趋化作用以及在某些 MC 类型中对 TNF-α 的产生中都具有冗余作用。相比之下，人类 MC 的反应仅依赖于 SphK1，这与该同工型的更强烈表达以及相对于鼠类 MC 而言 SphK 变体的更多样化表达相关。这些发现表明，SphK1 和 SphK2 在 MC 中的功能可以相互替代；然而，SphK 同工型用途的一个重要决定因素是物种来源以及一个影响因素，即 MC 可能来源于的组织和/或它们的分化状态。
