Protein tyrosine phosphatase 1B (PTP1B, also known as PTPN1) is an established regulator of cell-matrix adhesion and motility. However, the nature of substrate targets at adhesion sites remains to be validated. Here, we used bimolecular fluorescence complementation assays, in combination with a substrate trapping mutant of PTP1B, to directly examine whether relevant phosphotyrosines on paxillin and focal adhesion kinase (FAK, also known as PTK2) are substrates of the phosphatase in the context of cell-matrix adhesion sites. We found that the formation of catalytic complexes at cell-matrix adhesions requires intact tyrosine residues Y31 and Y118 on paxillin, and the localization of FAK at adhesion sites. Additionally, we found that PTP1B specifically targets Y925 on the focal adhesion targeting (FAT) domain of FAK at adhesion sites. Electrostatic analysis indicated that dephosphorylation of this residue promotes the closed conformation of the FAT 4-helix bundle and its interaction with paxillin at adhesion sites.

中文翻译：

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蛋白酪氨酸磷酸酶 1B 靶向细胞-基质粘附中的粘着斑激酶和桩蛋白。

蛋白酪氨酸磷酸酶 1B（PTP1B，也称为 PTPN1）是细胞基质粘附和运动的既定调节剂。然而，粘附部位的基材目标的性质仍有待验证。在这里，我们使用双分子荧光互补分析，结合 PTP1B 的底物捕获突变体，直接检查桩蛋白和粘着斑激酶（FAK，也称为 PTK2）上的相关磷酸酪氨酸是否是细胞背景下磷酸酶的底物 -基质粘附位点。我们发现在细胞-基质粘附处形成催化复合物需要桩蛋白上完整的酪氨酸残基 Y31 和 Y118，以及 FAK 在粘附位点的定位。此外，我们发现 PTP1B 在粘附部位的 FAK 的粘着斑靶向 (FAT) 域上专门针对 Y925。