Syndecans regulate cell migration thus having key roles in scarring and wound healing processes. Our previous results have shown that Thy-1/CD90 can engage both αvβ3 integrin and Syndecan-4 expressed on the surface of astrocytes to induce cell migration. Despite a well-described role of Syndecan-4 during cell movement, information is scarce regarding specific Syndecan-4 partners involved in Thy-1/CD90-stimulated cell migration. Mass spectrometry (MS) analysis of complexes precipitated with the Syndecan-4 cytoplasmic tail peptide was used to identify potential Syndecan-4-binding partners. The interactions found by MS were validated by immunoprecipitation and proximity ligation assays. The conducted research employed an array of genetic, biochemical and pharmacological approaches, including: PAR-3, Syndecan-4 and Tiam1 silencing, active Rac1 GEFs affinity precipitation, and video microscopy. We identified PAR-3 as a Syndecan-4-binding protein. Its interaction depended on the carboxy-terminal EFYA sequence present on Syndecan-4. In astrocytes where PAR-3 expression was reduced, Thy-1-induced cell migration and focal adhesion disassembly was impaired. This effect was associated with a sustained Focal Adhesion Kinase activation in the siRNA-PAR-3 treated cells. Our data also show that Thy-1/CD90 activates Tiam1, a PAR-3 effector. Additionally, we found that after Syndecan-4 silencing, Tiam1 activation was decreased and it was no longer recruited to the membrane. Syndecan-4/PAR-3 interaction and the alteration in focal adhesion dynamics were validated in mouse embryonic fibroblast (MEF) cells, thereby identifying this novel Syndecan-4/PAR-3 signaling complex as a general mechanism for mesenchymal cell migration involved in Thy-1/CD90 stimulation. The newly identified Syndecan-4/PAR-3 signaling complex participates in Thy-1/CD90-induced focal adhesion disassembly in mesenchymal cells. The mechanism involves focal adhesion kinase dephosphorylation and Tiam1 activation downstream of Syndecan-4/PAR-3 signaling complex formation. Additionally, PAR-3 is defined here as a novel adhesome-associated component with an essential role in focal adhesion disassembly during polarized cell migration. These novel findings uncover signaling mechanisms regulating cell migration, thereby opening up new avenues for future research on Syndecan-4/PAR-3 signaling in processes such as wound healing and scarring.

中文翻译：

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Syndecan-4/PAR-3 信号调节间充质细胞的粘着斑动力学。

Syndecans 调节细胞迁移，从而在疤痕形成和伤口愈合过程中发挥关键作用。我们之前的结果表明，Thy-1/CD90 可以与星形胶质细胞表面表达的 αvβ3 整联蛋白和 Syndecan-4 结合以诱导细胞迁移。尽管 Syndecan-4 在细胞运动过程中的作用得到了很好的描述，但关于参与 Thy-1/CD90 刺激的细胞迁移的特定 Syndecan-4 伙伴的信息很少。使用 Syndecan-4 胞质尾肽沉淀的复合物的质谱 (MS) 分析来鉴定潜在的 Syndecan-4 结合伙伴。MS 发现的相互作用通过免疫沉淀和邻近连接分析进行了验证。进行的研究采用了一系列遗传、生化和药理学方法，包括：PAR-3、Syndecan-4 和 Tiam1 沉默，活性 Rac1 GEFs 亲和沉淀和视频显微镜。我们将 PAR-3 鉴定为 Syndecan-4 结合蛋白。它的相互作用取决于 Syndecan-4 上存在的羧基末端 EFYA 序列。在 PAR-3 表达降低的星形胶质细胞中，Thy-1 诱导的细胞迁移和粘着斑分解受损。这种效应与 siRNA-PAR-3 处理的细胞中持续的粘着斑激酶激活有关。我们的数据还显示 Thy-1/CD90 激活 Tiam1，一种 PAR-3 效应器。此外，我们发现 Syndecan-4 沉默后，Tiam1 激活减少，不再被招募到膜上。Syndecan-4/PAR-3 相互作用和粘着斑动力学的改变在小鼠胚胎成纤维细胞 (MEF) 中得到验证，从而将这种新型 Syndecan-4/PAR-3 信号复合物鉴定为涉及 Thy-1/CD90 刺激的间充质细胞迁移的一般机制。新发现的 Syndecan-4/PAR-3 信号复合物参与了间充质细胞中 Thy-1/CD90 诱导的粘着斑分解。该机制涉及 Syndecan-4/PAR-3 信号复合物形成下游的粘着斑激酶去磷酸化和 Tiam1 激活。此外，PAR-3 在此被定义为一种新型粘附体相关成分，在极化细胞迁移过程中在粘着斑分解中起重要作用。这些新发现揭示了调节细胞迁移的信号机制，从而为未来研究伤口愈合和瘢痕形成等过程中的 Syndecan-4/PAR-3 信号通路开辟了新的途径。新发现的 Syndecan-4/PAR-3 信号复合物参与了间充质细胞中 Thy-1/CD90 诱导的粘着斑分解。该机制涉及 Syndecan-4/PAR-3 信号复合物形成下游的粘着斑激酶去磷酸化和 Tiam1 激活。此外，PAR-3 在此被定义为一种新型粘附体相关成分，在极化细胞迁移过程中在粘着斑分解中起重要作用。这些新发现揭示了调节细胞迁移的信号机制，从而为未来研究伤口愈合和瘢痕形成等过程中的 Syndecan-4/PAR-3 信号通路开辟了新的途径。新发现的 Syndecan-4/PAR-3 信号复合物参与了间充质细胞中 Thy-1/CD90 诱导的粘着斑分解。该机制涉及 Syndecan-4/PAR-3 信号复合物形成下游的粘着斑激酶去磷酸化和 Tiam1 激活。此外，PAR-3 在此被定义为一种新型粘附体相关成分，在极化细胞迁移过程中在粘着斑分解中起重要作用。这些新发现揭示了调节细胞迁移的信号机制，从而为未来研究伤口愈合和瘢痕形成等过程中的 Syndecan-4/PAR-3 信号通路开辟了新的途径。PAR-3 在此被定义为一种新的黏附体相关成分，在极化细胞迁移过程中在黏着斑分解中起重要作用。这些新发现揭示了调节细胞迁移的信号机制，从而为未来研究伤口愈合和瘢痕形成等过程中的 Syndecan-4/PAR-3 信号通路开辟了新的途径。PAR-3 在此被定义为一种新的黏附体相关成分，在极化细胞迁移过程中在黏着斑分解中起重要作用。这些新发现揭示了调节细胞迁移的信号机制，从而为未来研究伤口愈合和瘢痕形成等过程中的 Syndecan-4/PAR-3 信号通路开辟了新的途径。