Institute for Virology and Immunobiology, University of Wuerzburg, Wuerzburg, Germany.
Department of Cell Biology, Institute for Anatomy, University of Bern, Bern, Switzerland.
Front Immunol. 2018 Apr 18;9:815. doi: 10.3389/fimmu.2018.00815. eCollection 2018.
By promoting ceramide release at the cytosolic membrane leaflet, the neutral sphingomyelinase 2 (NSM) is capable of organizing receptor and signalosome segregation. Its role in T cell receptor (TCR) signaling remained so far unknown. We now show that TCR-driven NSM activation is dispensable for TCR clustering and initial phosphorylation, but of crucial importance for further signal amplification. In particular, at low doses of TCR stimulatory antibodies, NSM is required for Ca mobilization and T cell proliferation. NSM-deficient T cells lack sustained CD3ζ and ZAP-70 phosphorylation and are unable to polarize and stabilize their microtubular system. We identified PKCζ as the key NSM downstream effector in this second wave of TCR signaling supporting dynamics of microtubule-organizing center (MTOC). Ceramide supplementation rescued PKCζ membrane recruitment and MTOC translocation in NSM-deficient cells. These findings identify the NSM as essential in TCR signaling when dynamic cytoskeletal reorganization promotes continued lateral and vertical supply of TCR signaling components: CD3ζ, Zap70, and PKCζ, and functional immune synapses are organized and stabilized MTOC polarization.
通过促进细胞质膜小叶中的神经酰胺释放，中性鞘磷脂酶 2（NSM）能够组织受体和信号体的分离。它在 T 细胞受体（TCR）信号中的作用迄今尚不清楚。我们现在表明，TCR 驱动的 NSM 激活对于 TCR 聚集和初始磷酸化不是必需的，但对于进一步的信号放大至关重要。特别是，在 TCR 刺激抗体的低剂量下，NSM 对于 Ca 动员和 T 细胞增殖是必需的。缺乏 NSM 的 T 细胞缺乏持续的 CD3ζ 和 ZAP-70 磷酸化，并且无法极化和稳定其微管系统。我们确定 PKCζ 是支持微管组织中心（MTOC）动力学的 TCR 信号的第二个波中 NSM 的关键下游效应子。神经酰胺补充剂挽救了 NSM 缺陷细胞中 PKCζ 的膜募集和 MTOC 易位。这些发现确定了 NSM 在 TCR 信号转导中是必不可少的，当动态细胞骨架重排促进 TCR 信号转导成分（CD3ζ、Zap70 和 PKCζ）的持续侧向和垂直供应时，以及功能性免疫突触被组织和稳定 MTOC 极化。
