Medical Biotechnology, VTT Technical Research Centre of Finland, 20521 Turku, Finland.
Nat Cell Biol. 2011 Sep 25;13(11):1315-24. doi: 10.1038/ncb2340.
Regulated activation of integrins is critical for cell adhesion, motility and tissue homeostasis. Talin and kindlins activate β1-integrins, but the counteracting inhibiting mechanisms are poorly defined. We identified SHARPIN as an important inactivator of β1-integrins in an RNAi screen. SHARPIN inhibited β1-integrin functions in human cancer cells and primary leukocytes. Fibroblasts, leukocytes and keratinocytes from SHARPIN-deficient mice exhibited increased β1-integrin activity, which was fully rescued by re-expression of SHARPIN. We found that SHARPIN directly binds to a conserved cytoplasmic region of integrin α-subunits and inhibits recruitment of talin and kindlin to the integrin. Therefore, SHARPIN inhibits the critical switching of β1-integrins from inactive to active conformations.
整合素的调控激活对于细胞黏附、迁移和组织动态平衡至关重要。塔林蛋白和伴肌动蛋白激活β1 整合素,但对抗抑制机制知之甚少。我们在 RNAi 筛选中发现 SHARPIN 是β1 整合素的重要失活因子。SHARPIN 在人癌细胞和原代白细胞中抑制β1 整合素功能。缺乏 SHARPIN 的成纤维细胞、白细胞和角质细胞表现出增加的β1 整合素活性,而 SHARPIN 的重新表达完全挽救了这种活性。我们发现 SHARPIN 直接结合整合素α亚基的保守胞质区,并抑制塔林蛋白和伴肌动蛋白向整合素的募集。因此,SHARPIN 抑制β1 整合素从无活性构象向活性构象的关键转换。