Multiple post-translational modifications regulate E-cadherin transport during apoptosis
Multiple post-translational modifications regulate E-cadherin transport during apoptosis
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DOI：
10.1242/jcs.096735
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发表时间：
2012-06-01
影响因子：
4
通讯作者：
Andrews, David W.
中科院分区：
文献类型：
--
作者：
Geng, Fei;Zhu, Weijia;Andrews, David W.
E-钙粘蛋白作为前体合成，然后通过前蛋白转化酶进行切割。这种加工对于E-钙粘蛋白成熟和细胞粘附是必不可少的。细胞粘附的丧失导致凋亡诱导的细胞凋亡，这被称为失巢凋亡。失巢凋亡可以抑制，尽管损失的细胞-基质相互作用，通过保持E-钙粘蛋白介导的细胞-细胞粘附。相反，E-钙粘蛋白的急性缺失通过未知的翻译后机制使细胞对凋亡敏感。在用药物处理乳腺癌细胞后，我们发现E-cadherin的两种独立修饰抑制其细胞表面转运。首先，细胞质结构域的O-连接的β-N-乙酰葡糖胺（O-GlcNAc）修饰将E-钙粘蛋白保留在内质网中。第二，前蛋白转化酶的不完全加工在分泌途径的后期阻止了E-钙粘蛋白的转运。我们证明了这些E-钙粘蛋白修饰（通过特异性凝集素和抗体检测）不影响与α-连环蛋白、β-连环蛋白或γ-连环蛋白的结合。然而，E-钙粘蛋白与I型γ磷脂酰肌醇磷酸激酶（PIPKI γ）（一种将E-钙粘蛋白募集到粘附位点所需的蛋白质）的结合被O-GlcNAc糖基化（O-GlcNAc酰化）阻断。因此，E-钙粘蛋白运输到质膜被抑制。然而，不能被O-GlcNAc酰化的缺失突变体继续结合PIPKI γ，运输至细胞表面并延迟凋亡，证实了修饰和PIPKI γ结合的生物学意义。因此，E-钙粘蛋白的O-GlyNAc化加速了细胞凋亡。此外，细胞应激诱导的前蛋白转化酶失活，抑制E-钙粘蛋白成熟，进一步加剧细胞凋亡。通过O-GlcNAc化修饰E-钙粘蛋白和缺乏前区加工代表了响应中毒的E-钙粘蛋白的细胞表面转运的快速调节的新机制。
E-cadherin is synthesized as a precursor and then undergoes cleavage by proprotein convertases. This processing is essential for E-cadherin maturation and cell adhesion. Loss of cell adhesion causes detachment-induced apoptosis, which is called anoikis. Anoikis can be inhibited despite loss of cell-matrix interactions by preserving E-cadherin-mediated cell-cell adhesion. Conversely, acute loss of E-cadherin sensitizes cells to apoptosis by unknown post-translational mechanisms. After treatment of breast cancer cells with drugs, we found that two independent modifications of E-cadherin inhibit its cell surface transport. First, O-linked beta-N-acetylglucosamine (O-GlcNAc) modification of the cytoplasmic domain retains E-cadherin in the endoplasmic reticulum. Second, incomplete processing by proprotein convertases arrests E-cadherin transport late in the secretory pathway. We demonstrated these E-cadherin modifications (detected by specific lectins and antibodies) do not affect binding to alpha-catenin, beta-catenin or gamma-catenin. However, binding of E-cadherin to Type I gamma phosphatidylinositol phosphate kinase (PIPKI gamma), a protein required for recruitment of E-cadherin to adhesion sites, was blocked by O-GlcNAc glycosylation (O-GlcNAcylation). Consequently, E-cadherin trafficking to the plasma membrane was inhibited. However, deletion mutants that cannot be O-GlcNAcylated continued to bind PIPKI gamma, trafficked to the cell surface and delayed apoptosis, confirming the biological significance of the modifications and PIPKI gamma binding. Thus, O-GlyNAcylation of E-cadherin accelerates apoptosis. Furthermore, cell-stress-induced inactivation of proprotein convertases, inhibited E-cadherin maturation, further exacerbating apoptosis. The modifications of E-cadherin by O-GlcNAcylation and lack of pro-region processing represent novel mechanisms for rapid regulation of cell surface transport of E-cadherin in response to intoxication.