Gomez Juliana, Areeb Zammam, Stuart Sarah F, Nguyen Hong P T, Paradiso Lucia, Zulkifli Ahmad, Madan Sonakshi, Rajagopal Vijay, Montgomery Magdalene K, Gan Hui K, Scott Andrew M, Jones Jordan, Kaye Andrew H, Morokoff Andrew P, Luwor Rodney B
Department of Surgery, The University of Melbourne, The Royal Melbourne Hospital, Parkville, VIC 3050, Australia.
Cell Structure and Mechanobiology Group, Department of Biomedical Engineering, Melbourne School of Engineering, The University of Melbourne, Parkville, VIC 3010, Australia.
Cancers (Basel). 2021 Mar 10;13(6):1198. doi: 10.3390/cancers13061198.
Reticulocalbin 1 (RCN1) is an endoplasmic reticulum (ER)-residing protein, involved in promoting cell survival during pathophysiological conditions that lead to ER stress. However, the key upstream receptor tyrosine kinase that regulates RCN1 expression and its potential role in cell survival in the glioblastoma setting have not been determined. Here, we demonstrate that RCN1 expression significantly correlates with poor glioblastoma patient survival. We also demonstrate that glioblastoma cells with expression of EGFRvIII receptor also have high RCN1 expression. Over-expression of wildtype EGFR also correlated with high RCN1 expression, suggesting that EGFR and EGFRvIII regulate RCN1 expression. Importantly, cells that expressed EGFRvIII and subsequently showed high RCN1 expression displayed greater cell viability under ER stress compared to EGFRvIII negative glioblastoma cells. Consistently, we also demonstrated that RCN1 knockdown reduced cell viability and exogenous introduction of RCN1 enhanced cell viability following induction of ER stress. Mechanistically, we demonstrate that the EGFRvIII-RCN1-driven increase in cell survival is due to the inactivation of the ER stress markers ATF4 and ATF6, maintained expression of the anti-apoptotic protein Bcl-2 and reduced activity of caspase 3/7. Our current findings identify that EGFRvIII regulates RCN1 expression and that this novel association promotes cell survival in glioblastoma cells during ER stress.
网织钙结合蛋白1（RCN1）是一种内质网（ER）驻留蛋白，在导致内质网应激的病理生理条件下参与促进细胞存活。然而，调节RCN1表达的关键上游受体酪氨酸激酶及其在胶质母细胞瘤环境中细胞存活中的潜在作用尚未确定。在此，我们证明RCN1表达与胶质母细胞瘤患者的不良生存显著相关。我们还证明，表达EGFRvIII受体的胶质母细胞瘤细胞也具有高RCN1表达。野生型EGFR的过表达也与高RCN1表达相关，表明EGFR和EGFRvIII调节RCN1表达。重要的是，与EGFRvIII阴性的胶质母细胞瘤细胞相比，表达EGFRvIII并随后显示高RCN1表达的细胞在内质网应激下表现出更高的细胞活力。一致地，我们还证明，RCN1敲低降低了细胞活力，而内质网应激诱导后RCN1的外源导入增强了细胞活力。从机制上讲，我们证明EGFRvIII-RCN1驱动的细胞存活增加是由于内质网应激标志物ATF4和ATF6的失活、抗凋亡蛋白Bcl-2的持续表达以及caspase 3/7活性的降低。我们目前的研究结果表明，EGFRvIII调节RCN1表达，这种新的关联在胶质母细胞瘤细胞内质网应激期间促进细胞存活。
