Background

Proline-serine-threonine phosphatase interacting protein 1 (PSTPIP1) is a cytosolic adaptor protein involved with T-cell activation, differentiation, and migration. On cognate T-cell contact, PSTPIP1 is recruited to surface-expressed CD2, where it regulates F-actin remodeling. An immune synapse (IS) is thereby rapidly formed, consisting of T-cell receptor clusters surrounded by a ring of adhesion molecules, including CD2.

Objective

From genetic screening of patients with primary immunodeficiencies, we identified 2 mutations in PSTPIP1, R228C and T274M, which we further characterized in the primary patients' T cells.

Methods

F-actin dynamics were assessed in primary T cells from the patients and control subjects by using fluorescence-activated cell sorting. HEK293T and Jurkat cells were transfected with R228C, T274M, and wild-type PSTPIP1 to visualize F-actin in IS formation. CD2-PSTPIP1 association was quantified through immunoprecipitation assays.

Results

The patients presented with immunodeficiency without signs of autoinflammation. The patient with the R228C mutation had expansion of mostly naive phenotype T cells and few memory T cells; the patient with the T274M mutation had 75% reduction in CD4 T cells that were predominantly of the memory subset. We observed F-actin polymerization defects in T cells from both patients with PSTPIP1, most notably the patient with the T274M mutation. Capping of CD2-containing membrane microdomains was disrupted. Analysis of IS formation using Jurkat T-cell transfectants revealed a reduction in F-actin accumulation at the IS, again especially in cells from the patient with the T274M PSTPIP1 mutation. T cells from the patient with the T274M mutation migrated spontaneously at increased speed, as assessed in a 3-dimensional collagen matrix, whereas T-cell receptor cross-linking induced a significantly diminished calcium flux.

Conclusions

We propose that PSTPIP1 T-cell differentiation defects are caused by defective control of F-actin polymerization. A preactivated polymerized F-actin status, as seen in T cells from patients with the PSTPIP1 T274M mutation, appears particularly damaging. PSTPIP1 controls IS formation and cell adhesion through its function as an orchestrator of the F-actin cytoskeleton.

中文翻译：

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脯氨酸-丝氨酸-苏氨酸磷酸酶相互作用蛋白1（PSTPIP1）控制人T细胞中的免疫突触稳定性

背景

脯氨酸-丝氨酸-苏氨酸磷酸酶相互作用蛋白1（PSTPIP1）是参与T细胞活化，分化和迁移的胞质衔接蛋白。在关联的T细胞接触时，PSTPIP1被募集到表面表达的CD2，在那里它调节F-肌动蛋白的重塑。从而迅速形成了一个免疫突触（IS），它由被粘附分子环（包括CD2）包围的T细胞受体簇组成。

客观的

通过对原发性免疫缺陷患者的基因筛查，我们发现PSTPIP1，R228C和T274M中有2个突变，我们在原发性T细胞中进一步表征了这些突变。

方法

通过使用荧光激活细胞分选，评估了来自患者和对照对象的原代T细胞中的F-肌动蛋白动力学。用R228C，T274M和野生型PSTPIP1转染HEK293T和Jurkat细胞，以观察F-肌动蛋白在IS形成中的情况。CD2-PSTPIP1关联是通过免疫沉淀测定法定量的。

结果

患者表现为免疫缺陷，无自发炎症迹象。患有R228C突变的患者大部分为幼稚表型T细胞，少数为记忆T细胞。具有T274M突变的患者的CD4 T细胞减少了75％，而CD4 T细胞主要属于记忆亚群。我们观察到两名PSTPIP1患者（尤其是具有T274M突变的患者）的T细胞中F-肌动蛋白聚合缺陷。含CD2的膜微区的封顶被破坏。使用Jurkat T细胞转染子对IS形成的分析表明，F-肌动蛋白在IS处的蓄积减少，尤其是在来自T274M PSTPIP1突变患者的细胞中。在3维胶原蛋白基质中评估，患有T274M突变的患者的T细胞以自发的速度迁移，

结论

我们建议PSTPIP1 T细胞分化缺陷是由F-肌动蛋白聚合的缺陷控制引起的。从具有PSTPIP1 T274M突变的患者的T细胞中看到，预激活的聚合F-肌动蛋白状态似乎特别有害。PSTPIP1通过充当F-肌动蛋白细胞骨架的协调者来控制IS的形成和细胞粘附。