Institute of Nervous System Diseases, Xuzhou Medical University, Xuzhou, Jiangsu, China; Brain Hospital, Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, China; The Graduate School, Xuzhou Medical University, Xuzhou, Jiangsu, China.
Neuro Oncol. 2017 Nov 29;19(12):1628-1639. doi: 10.1093/neuonc/nox104.
Golgi phosphoprotein 3 (GOLPH3) is associated with worse prognosis of gliomas, but its role and mechanism in glioma progression remain largely unknown. This study aimed to explore the role and mechanism of GOLPH3 in glioma progression.
The expression of GOLPH3 in glioma tissues was detected by quantitative PCR, immunoblotting, and immunohistochemistry. GOLPH3's effect on glioma progression was examined using cell growth assays and an intracranial glioma model. The effect of GOLPH3 on epidermal growth factor receptor (EGFR) stability, endocytosis, and degradation was examined by immunoblotting and immunofluorescence. The activity of Rab5 was checked by glutathione S-transferase pulldown assay.
GOLPH3 was upregulated in gliomas, and its downregulation inhibited glioma cell proliferation both in vitro and in vivo. Furthermore, GOLPH3 depletion dampened EGFR signaling by enhancing EGFR endocytosis, driving EGFR into late endosome and promoting lysosome-mediated degradation. Interestingly, GOLPH3 bound to Rab5 and GOLPH3 downregulation promoted the activation of Rab5. In addition, Rab5 depletion abolished the effect of GOLPH3 on EGFR endocytosis and degradation.
Our results imply that GOLPH3 promotes glioma cell proliferation via inhibiting Rab5-mediated endocytosis and degradation of EGFR, thereby activating the phosphatidylinositol-3 kinase (PI3K)-Akt-mammalian target of rapamycin (mTOR) signaling pathway. We find a new mechanism by which GOLPH3 promotes tumor progression through regulating cell surface receptor trafficking. Extensive and intensive understanding of the role of GOLPH3 in glioma progression may provide an opportunity to develop a novel molecular therapeutic target for gliomas.
高尔基磷酸蛋白 3（GOLPH3）与神经胶质瘤的预后不良相关，但它在神经胶质瘤进展中的作用和机制在很大程度上尚不清楚。本研究旨在探讨 GOLPH3 在神经胶质瘤进展中的作用和机制。
通过定量 PCR、免疫印迹和免疫组织化学检测神经胶质瘤组织中 GOLPH3 的表达。通过细胞生长测定和颅内神经胶质瘤模型研究 GOLPH3 对神经胶质瘤进展的影响。通过免疫印迹和免疫荧光研究 GOLPH3 对表皮生长因子受体（EGFR）稳定性、内吞作用和降解的影响。通过谷胱甘肽 S-转移酶下拉测定检查 Rab5 的活性。
GOLPH3 在神经胶质瘤中上调，其下调抑制了体外和体内的神经胶质瘤细胞增殖。此外，GOLPH3 耗竭通过增强 EGFR 内吞作用，将 EGFR 驱动进入晚期内体并促进溶酶体介导的降解来抑制 EGFR 信号。有趣的是，GOLPH3 与 Rab5 结合，GOLPH3 下调促进了 Rab5 的激活。此外，Rab5 耗竭消除了 GOLPH3 对 EGFR 内吞作用和降解的影响。
我们的结果表明，GOLPH3 通过抑制 Rab5 介导的 EGFR 内吞作用和降解来促进神经胶质瘤细胞增殖，从而激活磷脂酰肌醇-3 激酶（PI3K）-Akt-雷帕霉素靶蛋白（mTOR）信号通路。我们发现了 GOLPH3 通过调节细胞表面受体转运促进肿瘤进展的新机制。对 GOLPH3 在神经胶质瘤进展中的作用的广泛和深入理解可能为开发神经胶质瘤的新型分子治疗靶标提供机会。
