Ovarian tumour domain-containing protein 3 (OTUD3), a key OTU (ovarian tumour protease) family deubiquitylase, plays context-dependent roles in cancers. It suppresses tumorigenesis in breast, colon, liver and cervical cancer through stabilizing PTEN (phosphatase and tension homologue deleted on chromosome 10) while promotes lung tumorigenesis through stabilizing GRP78 (The glucose-regulated protein 78 kDa). The regulation especially post-translational modification of OTUD3 remains unclear. Here, we report that the carboxyl terminus of Hsc70-interacting protein (CHIP) is a ubiquitin ligase for OTUD3. CHIP interacts with, polyubiquitylates OTUD3 and promotes OTUD3 degradation. Knockdown of CHIP stabilizes OTUD3 which leads to elevated GRP78 levels in lung cancer cells. CHIP-knockdown lung cancer cells exhibit increased invasion in OTUD3 and GRP78 dependent manner. Further study demonstrates that CHIP-knockdown lung cancer cells are more prone to metastasize to mice lung when injected intravenously or subcutaneously. Moreover, the expression of CHIP is low in human lung cancer tissues and inversely correlates with OTUD3 expression and GRP78 expression. Furthermore, we identified CHIP mutations in human lung cancers, which reduce CHIP catalytic activity. These findings demonstrate that CHIP is a negative regulator of OTUD3 and CHIP suppresses lung cancer metastasis through inhibiting OTUD3-GRP78 signaling axis.

含有卵巢肿瘤结构域的蛋白 3 (OTUD3) 是一种关键的 OTU（卵巢肿瘤蛋白酶）家族去泛素化酶，在癌症中发挥着上下文相关的作用。它通过稳定 PTEN（10 号染色体上缺失的磷酸酶和张力同源物）抑制乳腺癌、结肠癌、肝癌和宫颈癌的肿瘤发生，同时通过稳定 GRP78（葡萄糖调节蛋白 78 kDa）促进肺肿瘤发生。调节特别是 OTUD3 的翻译后修饰仍不清楚。在这里，我们报告 Hsc70 相互作用蛋白 (CHIP) 的羧基末端是 OTUD3 的泛素连接酶。CHIP 与 OTUD3 相互作用，使 OTUD3 多泛素化并促进 OTUD3 降解。敲除 CHIP 可以稳定 OTUD3，从而导致肺癌细胞中 GRP78 水平升高。CHIP 敲低的肺癌细胞以 OTUD3 和 GRP78 依赖性方式表现出增加的侵袭。进一步的研究表明，当静脉注射或皮下注射时，CHIP 敲低的肺癌细胞更容易转移到小鼠肺。此外，CHIP在人肺癌组织中的表达较低，与OTUD3表达和GRP78表达呈负相关。此外，我们在人类肺癌中发现了 CHIP 突变，这会降低 CHIP 催化活性。这些发现表明，CHIP 是 OTUD3 的负调节因子，CHIP 通过抑制 OTUD3-GRP78 信号轴来抑制肺癌转移。CHIP在人肺癌组织中的表达较低，与OTUD3表达和GRP78表达呈负相关。此外，我们在人类肺癌中发现了 CHIP 突变，这会降低 CHIP 催化活性。这些发现表明，CHIP 是 OTUD3 的负调节因子，CHIP 通过抑制 OTUD3-GRP78 信号轴来抑制肺癌转移。CHIP在人肺癌组织中的表达较低，与OTUD3表达和GRP78表达呈负相关。此外，我们在人类肺癌中发现了 CHIP 突变，这会降低 CHIP 催化活性。这些发现表明，CHIP 是 OTUD3 的负调节因子，CHIP 通过抑制 OTUD3-GRP78 信号轴来抑制肺癌转移。