Sphingomyelinase activation in T cells: Implications for T cell activation and paralysis

T细胞麻痹是麻疹病毒(MV)引起的全身性免疫抑制的主要标志。我们发现，中性的而不是酸性的鞘磷脂酶的激活以一种时间和空间受限的、协调的瞬时方式参与了生理T细胞的共刺激。这在MV与T细胞的相互作用中受到干扰，导致NSM和ASM的长期激活，这似乎与MV诱导共刺激的T细胞中肌动蛋白细胞骨架动力学的丧失有关。为了在鞘磷脂动力学水平上确定MV解除调节T细胞激活的分子靶点和途径，我们首先讨论了鞘磷脂酶在T细胞激活中的一般作用，并首先定义了它们在基础和刺激代谢T细胞编程中的重要性。因此，NSM的药理抑制提高了OXPHOS和糖酵解的总体水平，药理抑制了ASM的基础活性，防止了TCR刺激的氧化磷酸化(OXPHOS)的爆发。重要的是，MV阻断了TCR诱导的OXPHOS爆发，这一作用可被NSM抑制所阻止。在第二个资助期，我们将确定NSM或ASM对共刺激T细胞中OXPHOS与糖酵解的依赖调节的细胞靶点，以及MV对它们的潜在解除调节。其次，我们发现NSM是CD3信号转导所必需的，现在我们将从脂质和信号小体组成的水平上阐述NSM在CD3信号转导中的靶点和机制以及MV对其的调控。我们的第三个研究重点将采用完全相同的策略：CD28连接激活ASM似乎单独阻止了这种共刺激受体进入TCR信号机制。在抗原识别时，TCR发出的信号允许CD28通过取消ASM激活来进行共刺激。我们将通过共刺激受体来破译TCR介导的ASM激活沉默的机制。通过这一点，我们的目的是建立许可和沉默在神经鞘蛋白分解和/或神经酰胺释放的水平上是否是共同刺激和共同抑制的一般概念，明显的目的是评估如果这在MV相互作用中定性地解除调节的后果。

T cell paralysis is a major hallmark of measles virus (MV) induced generalized immunosuppression. We found that activation of the neutral, but not the acid sphingomyelinase takes part in physiological T cell co-stimulation in a timely and spatially restricted and coordinated transient manner. This is perturbed upon MV interaction with T cells, which causes prolonged activation of both NSM and ASM, and this appeared causatively linked to MV-induced loss of actin cytoskeletal dynamics in co-stimulated T cells. To identify molecular targets and pathways involved in MV deregulations of T cell activation at the level of sphingolipid dynamics, we first addressed the general role of sphingomyelinases in T cell activation and defined firstly, their importance in basal and stimulated metabolic T cell programming. Thus, pharmacological inhibition of NSM elevated general levels of both OXPHOS and glycolysis, and pharmacological inhibition of basal ASM activity prevented TCR stimulated oxidative phosphorylation (OXPHOS) bursting. Importantly, MV abrogated the TCR-induced OXPHOS burst, and and this was prevented by NSM inhibition. In the second funding period, we will identify cellular targets of NSM or ASM dependent regulation of OXPHOS versus glycolysis in co-stimulated T cells and their potential de-regulation by MV. Secondly, we found that NSM was required for CD3 signaling, and we will now address targets and mechanisms of NSM in CD3 signaling and their modulation by MV at the level of lipid and signalosome composition. The very same strategy will be employed for our third research focus: ASM activation by CD28 ligation alone appeared to prevent access of this co-stimulatory receptor to the TCR signaling machinery. Upon antigen recognition, signals emanating from the TCR licensed CD28 for co-stimulation by abrogating ASM activation. We will decipher mechanisms of TCR-mediated silencing of ASM activation by co-stimulating receptors. By this we aim to establish whether licensing versus silencing at the level of sphingomyelin breakdown and/or ceramide release is a general concept in co-stimulation and co-inhibition with the obvious goal to evaluate consequences if this is qualitatively de-regulated upon MV interaction.