Institute of Molecular and Clinical Immunology, Medical Faculty, Otto-von-Guericke University, 39120 Magdeburg, Germany.
Faculty of Biology, Signalling Research Centres BIOSS and CIBSS, University of Freiburg, 79085 Freiburg, Germany.
Cells. 2022 Sep 1;11(17):2723. doi: 10.3390/cells11172723.
Alterations in both the expression and function of the non-receptor tyrosine kinase Zap70 are associated with numerous human diseases including immunodeficiency, autoimmunity, and leukemia. Zap70 propagates the TCR signal by phosphorylating two important adaptor molecules, LAT and SLP76, which orchestrate the assembly of the signaling complex, leading to the activation of PLCγ1 and further downstream pathways. These events are crucial to drive T-cell development and T-cell activation. Recently, it has been proposed that C564, located in the kinase domain of Zap70, is palmitoylated. A non-palmitoylable C564R Zap70 mutant, which has been reported in a patient suffering from immunodeficiency, is incapable of propagating TCR signaling and activating T cells. The lack of palmitoylation was suggested as the cause of this human disease. Here, we confirm that Zap70 is signaling defective, but surprisingly, the defective Zap70 function does not appear to be due to a loss in palmitoylation. We engineered a C564A mutant of Zap70 which, similarly to Zap70, is non-palmitoylatable. However, this mutant was capable of propagating TCR signaling. Moreover, Zap70 enhanced the activity of Lck and increased its proximity to the TCR. Accordingly, Zap70-deficient P116 T cells expressing Zap70 displayed the hyperphosphorylation of TCR-ζ and Zap70 (Y319), two well-known Lck substrates. Collectively, these data indicate that C564 is important for the regulation of Lck activity and proximal TCR signaling, but not for the palmitoylation of Zap70.
Zap70 的表达和功能的改变与许多人类疾病有关，包括免疫缺陷、自身免疫和白血病。Zap70 通过磷酸化两个重要的衔接分子 LAT 和 SLP76 来传递 TCR 信号，这两个分子协调信号复合物的组装，导致 PLCγ1 的激活和下游途径的进一步激活。这些事件对于驱动 T 细胞发育和 T 细胞激活至关重要。最近，有人提出位于 Zap70 激酶结构域的 C564 被棕榈酰化。在患有免疫缺陷的患者中报道的非棕榈酰化 C564R Zap70 突变体无法传递 TCR 信号并激活 T 细胞。缺乏棕榈酰化被认为是这种人类疾病的原因。在这里，我们证实 Zap70 的信号传导有缺陷，但令人惊讶的是，缺陷 Zap70 功能似乎不是由于棕榈酰化的丧失。我们构建了 Zap70 的 C564A 突变体，类似于 Zap70，它不能被棕榈酰化。然而，这种突变体能够传递 TCR 信号。此外，Zap70 增强了 Lck 的活性并增加了其与 TCR 的接近度。因此，表达 Zap70 的 Zap70 缺陷型 P116 T 细胞显示 TCR-ζ 和 Zap70（Y319）的过度磷酸化，这是两个众所周知的 Lck 底物。总之，这些数据表明 C564 对于 Lck 活性和近端 TCR 信号的调节很重要，但对于 Zap70 的棕榈酰化不重要。
