EGFR signaling promotes nuclear translocation of plasma membrane protein TSPAN8 to enhance tumor progression via STAT3-mediated transcription
EGFR signaling promotes nuclear translocation of plasma membrane protein TSPAN8 to enhance tumor progression via STAT3-mediated transcription
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EGFR 信号传导促进质膜蛋白 TSPAN8 的核转位，通过 STAT3 介导的转录增强肿瘤进展
DOI：
10.1038/s41422-022-00628-8
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发表时间：
2022-02-23
期刊：
影响因子：
44.1
通讯作者：
Wang, Hongxia
中科院分区：
文献类型：
--
作者：
Lu, Xiaoqing;An, Liwei;Wang, Hongxia
TSPAN蛋白家族通常被认为在质膜上组装为多聚体复合物。我们之前的工作揭示了TSPAN 8可以作为无膜形式易位到细胞核中，这一过程需要TSPAN 8棕榈酰化并与胆固醇结合以促进其从质膜提取并随后与14-3-3θ和importin-β结合。然而，什么样的上游信号调节TSPAN 8的核转位，TSPAN 8在细胞核中的潜在功能以及潜在的分子机制都仍然不清楚。在这里，我们证明，表皮生长因子受体（EGFR）信号转导通过激活激酶AKT诱导TSPAN 8核转位，这反过来直接磷酸化TSPAN 8的Ser 129，这是其与14-3-3θ和输入素β 1结合所必需的事件。在细胞核中，磷酸化的TSPAN 8与STAT 3相互作用以增强其染色质占有率，从而调节下游促癌基因如MYC、BCL 2、MMP 9等的转录。EGFR-AKT-TSPAN 8-STAT 3轴被发现在多种人类癌症中过度活化，并且与侵袭性表型和令人沮丧的预后相关。我们进一步开发了人源化单克隆抗体hT 8Ab 4，其特异性识别TSPAN 8的大的细胞外环（TSPAN 8-LEL），从而能够阻断TSPAN 8从质膜的提取并因此阻断其核定位。重要的是，体外和体内研究都证明了hT 8Ab 4的抗肿瘤作用。总的来说，我们发现了TSPAN 8的一种非常规功能，并剖析了其潜在的分子机制，这不仅展示了传统膜蛋白的一层新的生物复杂性，而且揭示了TSPAN 8作为难治性癌症的一种新的治疗靶点。
TSPAN family of proteins are generally considered to assemble as multimeric complexes on the plasma membrane. Our previous work uncovered that TSPAN8 can translocate into the nucleus as a membrane-free form, a process that requires TSPAN8 palmitoylation and association with cholesterol to promote its extraction from the plasma membrane and subsequent binding with 14-3-3θ and importin-β. However, what upstream signal(s) regulate(s) the nuclear translocation of TSPAN8, the potential function of TSPAN8 in the nucleus, and the underlying molecular mechanisms all remain unclear. Here, we demonstrate that, epidermal growth factor receptor (EGFR) signaling induces TSPAN8 nuclear translocation by activating the kinase AKT, which in turn directly phosphorylates TSPAN8 at Ser129, an event essential for its binding with 14-3-3θ and importin ß1. In the nucleus, phosphorylated TSPAN8 interacts with STAT3 to enhance its chromatin occupancy and therefore regulates transcription of downstream cancer-promoting genes, such asMYC, BCL2, MMP9, etc. The EGFR–AKT–TSPAN8–STAT3 axis was found to be hyperactivated in multiple human cancers, and associated with aggressive phenotype and dismal prognosis. We further developed a humanized monoclonal antibody hT8Ab4that specifically recognizes the large extracellular loop of TSPAN8 (TSPAN8-LEL), thus being able to block the extraction of TSPAN8 from the plasma membrane and consequently its nuclear localization. Importantly, both in vitro and in vivo studies demonstrated an antitumor effect of hT8Ab4. Collectively, we discovered an unconventional function of TSPAN8 and dissected the underlying molecular mechanisms, which not only showcase a new layer of biological complexity of traditional membrane proteins, but also shed light on TSPAN8 as a novel therapeutic target for refractory cancers.