Department of Medical Biochemistry and Microbiology, Science for Life Laboratory, Uppsala University, Box 582, SE-751 23 Uppsala, Sweden.
Department of Medical Biosciences, Pathology Section, Umeå University, SE-901 87 Umeå, Sweden.
Sci Signal. 2022 Nov 15;15(760):eabp9521. doi: 10.1126/scisignal.abp9521.
Transforming growth factor-β (TGF-β) signaling has important roles during embryonic development and in tissue homeostasis. TGF-β ligands exert cellular effects by binding to type I (TβRI) and type II (TβRII) receptors and inducing both SMAD-dependent and SMAD-independent intracellular signaling pathways, the latter of which includes the activation of the tyrosine kinase Src. We investigated the mechanism by which TGF-β stimulation activates Src in human and mouse cells. Before TGF-β stimulation, inactive Src was complexed with TβRII. Upon TGF-β1 stimulation, TβRII associated with and phosphorylated TβRI at Tyr. Binding of Src to TβRI involved the interaction of the Src SH2 domain with phosphorylated Tyr and the interaction of the Src SH3 domain with a proline-rich region in TβRI and led to the activation of Src kinase activity and Src autophosphorylation. TGF-β1-induced Src activation required the kinase activities of TβRII and Src but not that of TβRI. Activated Src also phosphorylated TβRI on several tyrosine residues, which may stabilize the binding of Src to the receptor. Src activation was required for the ability of TGF-β to induce fibronectin production and migration in human breast carcinoma cells and to induce α-smooth muscle actin and actin reorganization in mouse fibroblasts. Thus, TGF-β induces Src activation by stimulating a direct interaction with TβRI that depends on tyrosine phosphorylation of TβRI by TβRII.
转化生长因子-β（TGF-β）信号在胚胎发育和组织稳态中具有重要作用。TGF-β配体通过与 I 型（TβRI）和 II 型（TβRII）受体结合，诱导 SMAD 依赖性和非 SMAD 依赖性细胞内信号通路，从而发挥细胞效应，后者包括酪氨酸激酶Src 的激活。我们研究了 TGF-β刺激在人源和鼠源细胞中激活Src 的机制。在 TGF-β刺激之前，无活性的 Src 与 TβRII 结合。在 TGF-β1 刺激下，TβRII 与 TβRI 结合并磷酸化 Tyr。Src 与 TβRI 的结合涉及 Src SH2 结构域与磷酸化 Tyr 的相互作用和 Src SH3 结构域与 TβRI 中富含脯氨酸的区域的相互作用，导致 Src 激酶活性和 Src 自身磷酸化的激活。TGF-β1 诱导的 Src 激活需要 TβRII 和 Src 的激酶活性，但不需要 TβRI 的激酶活性。激活的 Src 还在几个酪氨酸残基上磷酸化 TβRI，这可能稳定 Src 与受体的结合。Src 的激活对于 TGF-β诱导人乳腺癌细胞产生纤维连接蛋白和迁移以及诱导鼠成纤维细胞α-平滑肌肌动蛋白和肌动蛋白重排的能力是必需的。因此，TGF-β 通过刺激与 TβRI 的直接相互作用来诱导 Src 激活，该相互作用依赖于 TβRII 对 TβRI 的酪氨酸磷酸化。
