Department of Pathology &Cell Biology, Columbia University, P&S 15-420, 630 West 168th Street, New York, New York 10032, USA.
Nat Cell Biol. 2016 May;18(5):491-503. doi: 10.1038/ncb3333. Epub 2016 Apr 4.
Integrin endocytic recycling is critical for cell migration, yet how recycled integrins assemble into new adhesions is unclear. By synchronizing endocytic disassembly of focal adhesions (FAs), we find that recycled integrins reassemble FAs coincident with their return to the cell surface and dependent on Rab5 and Rab11. Unexpectedly, endocytosed integrins remained in an active but unliganded state in endosomes. FAK and Src kinases co-localized with endocytosed integrin and were critical for FA reassembly by regulating integrin activation and recycling, respectively. FAK sustained the active integrin conformation by maintaining talin association with Rab11 endosomes in a type I phosphatidylinositol phosphate kinase (PIPKIγ)-dependent manner. In migrating cells, endocytosed integrins reassembled FAs polarized towards the leading edge, and this polarization required FAK. These studies identify unanticipated roles for FA proteins in maintaining endocytosed integrin in an active conformation. We propose that the conformational memory of endocytosed integrin enhances polarized reassembly of FAs to enable directional cell migration.
整合素的内吞循环对于细胞迁移至关重要，但回收的整合素如何重新组装成新的黏附结构尚不清楚。通过同步细胞内焦点黏附（FA）的内吞作用解体，我们发现回收的整合素与它们返回细胞表面时重新组装 FA，这一过程依赖于 Rab5 和 Rab11。出乎意料的是，内吞的整合素在内涵体内仍然处于活跃但未配体结合的状态。FAK 和Src 激酶与内吞的整合素共定位，通过分别调节整合素的激活和回收，对于 FA 的重新组装至关重要。FAK 通过维持 Rab11 内涵体与 talin 的关联，以一种Ⅰ型磷酸肌醇磷酸激酶（PIPKIγ）依赖性的方式维持活性整合素构象。在迁移的细胞中，内吞的整合素重新组装成 FA，向细胞前缘极化，而这种极化需要 FAK。这些研究确定了 FA 蛋白在维持内吞的整合素处于活性构象方面的预期作用。我们提出，内吞的整合素的构象记忆增强了 FA 的极化重排，从而使细胞能够进行定向迁移。
