Hallym Translational Research Institute, Hallym University Sacred Heart Hospital, Anyang-si, 14054, Republic of Korea.
Division of Hematology-Oncology, Department of Internal Medicine, Hallym University Sacred Heart Hospital, Hallym University College of Medicine, 22, Gwanpyeong-ro 170, beon-gil, Dongan-gu, Anyang‑si, Gyeonggi‑do, 14068, Republic of Korea.
Sci Rep. 2022 Apr 29;12(1):7013. doi: 10.1038/s41598-022-10868-8.
RING finger protein 43 (RNF43) encodes the transmembrane E3 ubiquitin ligase, which targets the Wnt receptor Frizzled (FZD). RNF43 mutations have been discovered in various human cancers including colon, pancreatic, stomach, ovarian, and liver cancers. Functional studies on RNF43 missense mutations have shown that they negatively regulate Wnt signaling; however, there are few functional studies on RNF43 frameshift mutations. In this study, we showed that R117fs and P441fs mutants enhanced Wnt/β-catenin signaling, whereas Q409fs and G659fs mutants retained the ability to suppress Wnt/β-catenin signaling. Specifically, R117fs was unable to ubiquitinate FZD5 due to lack of the RING domain, although it was able to interact with FZD5. Immunofluorescence showed that R117fs failed to internalize FZD5 expressed on the cell surface. We also showed that LGK974, a potent Wnt inhibitor, decreased the Wnt/β-catenin activity by R117fs and P441fs mutations. Together, these results demonstrate that RNF43 frameshift mutations retain normal functionality; thus, targeted anti-cancer therapy can be developed according to the mutation type of RNF43.
环指蛋白 43（RNF43）编码跨膜 E3 泛素连接酶，其靶向 Wnt 受体卷曲（FZD）。RNF43 突变已在各种人类癌症中发现，包括结肠癌、胰腺癌、胃癌、卵巢癌和肝癌。对 RNF43 错义突变的功能研究表明，它们负调控 Wnt 信号；然而，对 RNF43 移码突变的功能研究较少。在这项研究中，我们表明 R117fs 和 P441fs 突变体增强了 Wnt/β-连环蛋白信号，而 Q409fs 和 G659fs 突变体保留了抑制 Wnt/β-连环蛋白信号的能力。具体来说，由于缺乏 RING 结构域，R117fs 无法泛素化 FZD5，尽管它能够与 FZD5 相互作用。免疫荧光显示，由于缺乏 RING 结构域，R117fs 无法内化表达在细胞表面的 FZD5。我们还表明，强效 Wnt 抑制剂 LGK974 可降低由 R117fs 和 P441fs 突变引起的 Wnt/β-连环蛋白活性。总之，这些结果表明 RNF43 移码突变保留了正常的功能；因此，可以根据 RNF43 的突变类型开发靶向抗癌疗法。
