Spry2 is a molecular modulator of tyrosine kinase receptor signaling pathways that has cancer-type-specific effects. Mammalian Spry2 protein undergoes tyrosine and serine phosphorylation in response to growth factor stimulation. Spry2 expression is distinctly altered in various cancer types. Inhibition of the proteasome functionality results in reduced intracellular Spry2 degradation. Using in vitro and in vivo assays, we show that protein kinase D (PKD) phosphorylates Spry2 at serine 112 and interacts in vivo with the C-terminal half of this protein. Importantly, missense mutation of Ser112 decreases the rate of Spry2 intracellular protein degradation. Either knocking down the expression of all three mammalian PKD isoforms or blocking their kinase activity with a specific inhibitor contributes to the stabilization of Spry2 wild-type protein. Downregulation of CSN3, a component of the COP9/Signalosome that binds PKD, significantly increases the half-life of Spry2 wild-type protein but does not affect the stability of a Spry2 after mutating Ser112 to the non-phosphorylatable residue alanine. Our data demonstrate that both PKD and the COP9/Signalosome play a significant role in control of Spry2 intracellular stability and support the consideration of the PKD/COP9 complex as a potential therapeutic target in tumors where Spry2 expression is reduced.

Spry2 是酪氨酸激酶受体信号通路的分子调节剂，具有癌症类型特异性作用。哺乳动物 Spry2 蛋白响应生长因子刺激而经历酪氨酸和丝氨酸磷酸化。Spry2 表达在各种癌症类型中明显改变。蛋白酶体功能的抑制导致细胞内 Spry2 降解减少。使用体外和体内测定，我们显示蛋白激酶 D (PKD) 在丝氨酸 112 磷酸化 Spry2，并在体内与该蛋白质的 C 末端一半相互作用。重要的是，Ser112 的错义突变降低了 Spry2 细胞内蛋白质降解的速率。敲低所有三种哺乳动物 PKD 亚型的表达或用特定抑制剂阻断它们的激酶活性有助于 Spry2 野生型蛋白的稳定。CSN3（结合 PKD 的 COP9/Signalosome 的一个组成部分）的下调显着增加了 Spry2 野生型蛋白的半衰期，但在将 Ser112 突变为不可磷酸化的残基丙氨酸后不影响 Spry2 的稳定性。我们的数据表明，PKD 和 COP9/Signalosome 在控制 Spry2 细胞内稳定性方面发挥着重要作用，并支持考虑将 PKD/COP9 复合物作为 Spry2 表达降低的肿瘤的潜在治疗靶点。