Walker Timothy J, Reyes-Alvarez Eduardo, Hyndman Brandy D, Sugiyama Michael G, Oliveira Larissa C B, Rekab Aisha N, Crupi Mathieu J F, Cabral-Dias Rebecca, Guo Qianjin, Dahia Patricia L M, Richardson Douglas S, Antonescu Costin N, Mulligan Lois M
Division of Cancer Biology and Genetics, Cancer Research Institute, and Department of Pathology and Molecular Medicine, Queen's University, Kingston, ON, K7L 3N6, Canada.
Department of Chemistry and Biology, Toronto Metropolitan University, Toronto, ON, M5B 2K3, Canada.
bioRxiv. 2024 Apr 3:2023.06.28.546955. doi: 10.1101/2023.06.28.546955.
Internalization from the cell membrane and endosomal trafficking of receptor tyrosine kinases (RTK) are important regulators of signaling in normal cells that can frequently be disrupted in cancer. The adrenal tumour pheochromocytoma (PCC) can be caused by activating mutations of the RET receptor tyrosine kinase, or inactivation of TMEM127, a transmembrane tumour suppressor implicated in trafficking of endosomal cargos. However, the role of aberrant receptor trafficking in PCC is not well understood. Here, we show that loss of TMEM127 causes wildtype RET protein accumulation on the cell surface, where increased receptor density facilitates constitutive ligand-independent activity and downstream signaling, driving cell proliferation. Loss of TMEM127 altered normal cell membrane organization and recruitment and stabilization of membrane protein complexes, impaired assembly, and maturation of clathrin coated pits, and reduced internalization and degradation of cell surface RET. In addition to RTKs, TMEM127 depletion also promoted surface accumulation of several other transmembrane proteins, suggesting it may cause global defects in surface protein activity and function. Together, our data identify TMEM127 as an important determinant of membrane organization including membrane protein diffusability, and protein complex assembly and provide a novel paradigm for oncogenesis in PCC where altered membrane dynamics promotes cell surface accumulation and constitutive activity of growth factor receptors to drive aberrant signaling and promote transformation.
受体酪氨酸激酶（RTK）从细胞膜的内化及内体运输是正常细胞信号传导的重要调节因子，而在癌症中这些过程常常被破坏。肾上腺肿瘤嗜铬细胞瘤（PCC）可能由RET受体酪氨酸激酶的激活突变或TMEM127的失活引起，TMEM127是一种参与内体货物运输的跨膜肿瘤抑制因子。然而，异常受体运输在PCC中的作用尚未完全明确。在此，我们表明TMEM127的缺失导致野生型RET蛋白在细胞表面积累，受体密度增加促进了组成型非配体依赖性活性及下游信号传导，从而驱动细胞增殖。TMEM127的缺失改变了正常细胞膜组织以及膜蛋白复合物的募集和稳定，损害了网格蛋白包被小窝的组装和成熟，并减少了细胞表面RET的内化和降解。除了RTK外，TMEM127的缺失还促进了其他几种跨膜蛋白的表面积累，表明它可能导致表面蛋白活性和功能的整体缺陷。总之，我们的数据确定TMEM127是膜组织的重要决定因素，包括膜蛋白扩散性、蛋白复合物组装，并为PCC的肿瘤发生提供了一种新的模式，即改变的膜动力学促进生长因子受体在细胞表面的积累和组成型活性，从而驱动异常信号传导并促进细胞转化。
