三阴性乳腺癌（TNBC）无法治愈，并且容易发生广泛转移。因此，迫切需要确定 TNBC 进展的关键靶点。我们之前的研究表明，异楝素 (ITSN) 通过靶向 TGFβR1 减少 TNBC 转移。 ITSN目前被用作有效的化学探针，以进一步发现TGFβR1下游参与TNBC转移的关键分子。结果表明，GOT2是Smad2/3的下游基因，ITSN通过直接结合TGFβR1，消除TGF-β-Smad2/3信号通路的激活，从而降低GOT2的表达。 GOT2 在 TNBC 中高表达，其敲低可减少 TNBC 转移。然而，GOT2 过表达逆转了 ITSN 对体外和体内 TNBC 转移的抑制作用。 GOT2与MYH9相互作用并阻碍其与E3泛素连接酶STUB1的结合，从而减少MYH9泛素化和降解。此外，GOT2还增强MYH9向线粒体的易位，从而诱导DRP1磷酸化，从而促进TNBC细胞中线粒体裂变和板状伪足形成。 ITSN 介导的线粒体裂变和片状伪足形成抑制与 GOT2 表达减少相关。总之，ITSN 通过减少 GOT2 表达来增强 MYH9 蛋白降解，从而防止 TNBC 细胞中 MYH9 调节的线粒体裂变和板状伪足形成，从而有助于抑制 TNBC 转移。© 2024。作者，独家许可中国科学院上海药物研究所、中国药理学会。

Triple-negative breast cancer (TNBC) is incurable and prone to widespread metastasis. Therefore, identification of key targets for TNBC progression is urgently needed. Our previous study revealed that isotoosendanin (ITSN) reduced TNBC metastasis by targeting TGFβR1. ITSN is currently used as an effective chemical probe to further discover the key molecules involved in TNBC metastasis downstream of TGFβR1. The results showed that GOT2 was the gene downstream of Smad2/3 and that ITSN decreased GOT2 expression by abrogating the activation of the TGF-β-Smad2/3 signaling pathway through directly binding to TGFβR1. GOT2 was highly expressed in TNBC, and its knockdown decreased TNBC metastasis. However, GOT2 overexpression reversed the inhibitory effect of ITSN on TNBC metastasis both in vitro and in vivo. GOT2 interacted with MYH9 and hindered its binding to the E3 ubiquitin ligase STUB1, thereby reducing MYH9 ubiquitination and degradation. Moreover, GOT2 also enhanced the translocation of MYH9 to mitochondria and thus induced DRP1 phosphorylation, thereby promoting mitochondrial fission and lamellipodia formation in TNBC cells. ITSN-mediated inhibition of mitochondrial fission and lamellipodia formation was associated with reduced GOT2 expression. In conclusion, ITSN prevented MYH9-regulated mitochondrial fission and lamellipodia formation in TNBC cells by enhancing MYH9 protein degradation through a reduction in GOT2 expression, thus contributing to its inhibition of TNBC metastasis.© 2024. The Author(s), under exclusive licence to Shanghai Institute of Materia Medica, Chinese Academy of Sciences and Chinese Pharmacological Society.