GCN2-SLC7A11 axis coordinates autophagy, cell cycle and apoptosis and regulates cell growth in retinoblastoma upon arginine deprivation

Background: Arginine deprivation was shown previously to inhibit retinoblastoma cell proliferation and induce cell death in vitro. However, the mechanisms by which retinoblastoma cells respond to arginine deprivation remain to be elucidated. Methods: Human derived retinoblastoma cell lines Y79 and WERI-Rb-1 were exposed to arginine depletion, and the effects on inhibiting cell growth and survival were evaluated. The study investigated potential mechanisms, including autophagy, cell cycle arrest, and apoptosis. Moreover, the roles of GCN2 and mTOR signaling pathways in these processes were examined. Results: We demonstrated that arginine deprivation effectively inhibited the growth of retinoblastoma cells in vitro. This treatment caused an increase in autophagic response. Additionally, we found that prolonged arginine shortage induced G2 cell cycle arrest and was accompanied by an increase in early apoptotic cells. Importantly, arginine depletion also caused an activation of GCN2 and an inhibition of mTOR signaling. We also discovered that the activation of SLC7A11 was regulated by GCN2 upon arginine deprivation. Knockdown of SLC7A11 rendered retinoblastoma cells partially resistant to arginine deprivation. Furthermore, we found that knockdown of GCN2 led to a decrease in autophagic response in WERI-Rb-1 cells and arrested more cells in S phase, which was accompanied by fewer apoptotic cells. Moreover, knockdown of GCN2 caused constant expression of ATF4, phosphorylation of 70S6K, and 4E-BP1 regardless of arginine deprivation. Conclusions: Collectively, our findings suggest that the GCN2-SLC7A11 axis regulates cell growth and survival upon arginine deprivation through coordinating autophagy, cell cycle arrest, and apoptosis in retinoblastoma cells. This work paves the way for the development of a novel treatment for retinoblastoma.