This study aims to explore the function and mechanism of G Protein-coupled receptor class C group 5 member A (GPRC5A) in docetaxel-resistance and liver metastasis of breast cancer. Single-cell RNA transcriptomic analysis and bioinformatic analysis are used to screen relevant genes in breast cancer metastatic hepatic specimens. MeRIP, dual-luciferase analysis and bioinformation were used to detect m6A modulation. Mass spectrometry (MS), co-inmunoprecipitation (co-IP) and immunofluorescence colocalization were executed to explore the mechanism of GPRC5A in breast cancer cells. GPRC5A was upregulated in triple-negative breast cancer (TNBC) and was associated with a poor prognosis. In vitro and in vivo experiments demonstrated that knockdown of GPRC5A alleviated metastasis and resistance to docetaxel in TNBC. Overexpression of GPRC5A had the opposite effects. The m6A methylation of GPRC5A mRNA was modulated by METTL3 and YTHDF1, which facilitates its translation. GPRC5A inhibited the ubiquitination-dependent degradation of LAMTOR1, resulting in the recruitment of mTORC1 to lysosomes and activating the mTORC1/p70s6k signaling pathway. METTL3/YTHDF1 axis up-regulates GPRC5A expression by m6A methylation. GPRC5A activates mTORC1/p70s6k signaling pathway by recruiting mTORC1 to lysosomes, consequently promotes docetaxel-resistance and liver metastasis.

中文翻译：

---

GPRC5A甲基化通过激活三阴性乳腺癌mTOR信号通路促进肝转移和多西他赛耐药

本研究旨在探讨G蛋白偶联受体C类5成员A（GPRC5A）在乳腺癌多西紫杉醇耐药和肝转移中的功能和机制。利用单细胞RNA转录组分析和生物信息学分析筛选乳腺癌转移性肝标本中的相关基因。MeRIP、双荧光素酶分析和生物信息用于检测 m6A 调制。采用质谱（MS）、免疫共沉淀（co-IP）和免疫荧光共定位来探索GPRC5A在乳腺癌细胞中的作用机制。GPRC5A 在三阴性乳腺癌 (TNBC) 中表达上调，并与不良预后相关。体外和体内实验表明，敲低 GPRC5A 可减轻 TNBC 中的转移和对多西他赛的耐药性。GPRC5A 的过度表达具有相反的效果。GPRC5A mRNA 的 m6A 甲基化受到 METTL3 和 YTHDF1 的调节，从而促进其翻译。GPRC5A 抑制 LAMTOR1 的泛素化依赖性降解，导致 mTORC1 募集到溶酶体并激活 mTORC1/p70s6k 信号通路。METTL3/YTHDF1 轴通过 m6A 甲基化上调 GPRC5A 表达。GPRC5A通过将mTORC1招募到溶酶体来激活mTORC1/p70s6k信号通路，从而促进多西紫杉醇耐药和肝转移。