The two non-visual subtypes, arrestin-2 and arrestin-3, are ubiquitously expressed and bind hundreds of G protein-coupled receptors. In addition, these arrestins also interact with dozens of non-receptor signaling proteins, including c-Src, ERK and JNK, that regulate cell death and survival. Arrestin-3 facilitates the activation of JNK family kinases, which are important players in the regulation of apoptosis. Here we show that arrestin-3 is specifically cleaved at Asp366, Asp405 and Asp406 by caspases during the apoptotic cell death. This results in the generation of one main cleavage product, arrestin-3-(1-366). The formation of this fragment occurs in a dose-dependent manner with the increase of fraction of apoptotic cells upon etoposide treatment. In contrast to a caspase-resistant mutant (D366/405/406E) the arrestin-3-(1-366) fragment reduces the apoptosis of etoposide-treated cells. We found that caspase cleavage did not affect the binding of the arrestin-3 to JNK3, but prevented facilitation of its activation, in contrast to the caspase-resistant mutant, which facilitated JNK activation similar to WT arrestin-3, likely due to decreased binding of the upstream kinases ASK1 and MKK4/7. The data suggest that caspase-generated arrestin-3-(1-366) prevents the signaling in the ASK1-MKK4/7-JNK1/2/3 cascade and protects cells, thereby suppressing apoptosis.

中文翻译：

---

半胱氨酸蛋白酶对restarin-3的切割通过阻止restarin依赖的JNK激活来减弱细胞死亡。

两种非视觉亚型，抑制蛋白2和抑制蛋白3普遍存在，并结合数百种G蛋白偶联受体。另外，这些抑制蛋白还与调节细胞死亡和存活的数十种非受体信号蛋白相互作用，包括c-Src，ERK和JNK。Arrestin-3促进JNK家族激酶的激活，而JNK家族激酶在细胞凋亡的调控中起着重要的作用。在这里，我们显示，在凋亡细胞死亡期间，胱天蛋白酶会特异性地使restarin-3在Asp366，Asp405和Asp406处裂解。这导致产生一种主要的裂解产物，抑制蛋白-3-（1-366）。依托泊苷处理后，随着凋亡细胞比例的增加，该片段的形成以剂量依赖性方式发生。与耐半胱天冬酶的突变体（D366 / 405 / 406E）相反，restarin-3-（1-366）片段减少了依托泊苷处理细胞的凋亡。我们发现，与胱天蛋白酶抗性突变体相反，胱天蛋白酶裂解不影响restarin-3与JNK3的结合，但阻止了其激活的促进，与突变体crestase-3类似，caspase耐药突变体促进了JNK的激活，这可能是由于结合力降低所致。上游激酶ASK1和MKK4 / 7的表达。数据表明，胱天蛋白酶产生的抑制蛋白-3-（1-366）阻止了ASK1-MKK4 / 7-JNK1 / 2/3级联中的信号传导并保护了细胞，从而抑制了细胞凋亡。可能是由于上游激酶ASK1和MKK4 / 7的结合减少，从而促进了与WT抑制蛋白3相似的JNK活化。数据表明，胱天蛋白酶产生的抑制蛋白-3-（1-366）阻止了ASK1-MKK4 / 7-JNK1 / 2/3级联中的信号传导并保护了细胞，从而抑制了细胞凋亡。可能是由于上游激酶ASK1和MKK4 / 7的结合减少，从而促进了与WT抑制蛋白3相似的JNK活化。数据表明，胱天蛋白酶产生的抑制蛋白-3-（1-366）阻止了ASK1-MKK4 / 7-JNK1 / 2/3级联中的信号传导并保护了细胞，从而抑制了细胞凋亡。