Inhibition of γ ray-induced apoptosis by stimulatory heterotrimeric GTP binding protein involves Bcl-xL down-regulation in SH-SY5Y human neuroblastoma cells

Abstract

Heterotrimeric GTP-binding proteins (G proteins) transduce extracellular signals into intracellular signals by activating effector molecules including adenylate cyclases that catalyze cAMP formation, and thus regulate various cellular responses such as metabolism, proliferation, and apoptosis. cAMP signaling pathways have been reported to protect cells from ionizing radiation-induced apoptosis, but however, the protective mechanism is not clear. Therefore, this study aimed to investigate the signaling molecules and the mechanism mediating the anti-apoptotic action of cAMP signaling system in radiation-induced apoptosis. Stable expression of a constitutively active mutant of Gα s (Gα sQL) protected gamma ray-induced apoptosis which was assessed by analysis of the cleavages of PARP, caspase-9, and caspase-3 and cytochrome C release in SH-SY5Y human neuroblastoma cells. GαsQL repressed the gamma ray-induced down-regulation of Bcl-xL protein, but transfection of Bcl-xL siRNA increased the gamma ray-induced apoptosis and abolished the anti-apoptotic effect of Gα sQL. Gα sQL decreased the degradation rate of Bcl-xL protein, and it also restrained the decrease in Bcl-xL mRNA by increasing the stability following ionizing irradiation. Furthermore, prostaglandin E2 that activates Gαs was found to protect gamma ray-induced apoptosis, and the protective effect was abolished by treatment with prostanoid receptor antagonist specific to EP2/4R subtype. Moreover, specific agonists for adenosine A1 receptor that inhibits cAMP signaling pathway augmented gamma ray-induced apoptosis. From this study, it is concluded that Gαs-cAMP signaling system can protect SH-SY5Y cells from gamma ray-induced apoptosis partly by restraining down-regulation of Bcl-xL expression, suggesting that radiation-induced apoptosis can be modulated by GPCR ligands to improve the efficiency of radiation therapy.

Radioprotective effects of genistein on HL-7702 cells via the inhibition of apoptosis and DNA damage

“…In many cases, the radiation-induced cell damage results in apoptosis [31]. In our present study, low GEN dosage exerted its protective action on L-02 cell viability, as evidenced by decreasing the apoptosis rate induced by X-ray irradiation.…”

GNAS1 T393C polymorphism is associated with histopathological response to neoadjuvant radiochemotherapy in esophageal cancer

“…21 The underlying mechanism was only recently elucidated, showing that Gs inhibits radiation-induced apoptosis by restraining downregulation of Bcl-xl. 39 The cAMP-dependent protein kinase signaling pathway also seems to be involved in the acquisition of cisplatin resistance after irradiation. 40 It has been recently shown that the CC genotype of T393C polymorphism shows the lowest GNAS1 expression.…”

Stimulatory heterotrimeric G protein augments gamma ray-induced apoptosis by up-regulation of Bak expression via CREB and AP-1 in H1299 human lung cancer cells

“…Furthermore, we showed that PGE2 augmented gamma ray-induced apoptosis of H1299 cells via Gαs-coupled receptor, as stimulation of beta-adrenergic receptor induced cell death of thymocytes (Gu et al, 2000). However, Gαs protein was reported to inhibit radiation-or hydrogen peroxide-induced apoptosis of SH-SY5Y human neuroblastoma cells (Kim et al, 2007(Kim et al, , 2008. Inhibitory G proteins were found to antagonize the anti-apoptotic effect of Gαs in hydrogen peroxide-treated SH-SY5Y human neuroblastoma cells (Kim et al, 2008) and also to inhibit hydrogen peroxide-induced apoptosis by up-regulation of Bcl-2 via NF-κB in H1299 human lung cancer cells (Seo et al, 2009).…”

“…The expression of proteins was analyzed by western blotting using specific antibodies as described previously (Kim et al, 2007). Antibodies against β-actin and Bcl-2 were purchased from Santa Cruz Biotechnology (Santa Cruz, CA), antibodies against PARP, cleaved PARP, cleaved caspase-3, Bax, Bcl-XL, and Bak were obtained from Cell Signaling Technology (Beverly, MA).…”