Exp Mol Med.  2009 Aug;41(8):592-600. 10.3858/emm.2009.41.8.065.

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

• Choi YJ
• Kim SY
• Oh JM
• Juhnn YS

• KMID: 1119325
• DOI: http://doi.org/10.3858/emm.2009.41.8.065

Abstract

Stimulatory heterotrimeric GTP-binding proteins (Gs protein) stimulate cAMP generation in response to various signals, and modulate various cellular phenomena such as proliferation and apoptosis. This study aimed to investigate the effect of Gs proteins on gamma ray-induced apoptosis of lung cancer cells and its molecular mechanism, as an attempt to develop a new strategy to improve the therapeutic efficacy of gamma radiation. Expression of constitutively active mutant of the alpha subunit of Gs (GalphasQL) augmented gamma ray-induced apoptosis via mitochondrial dependent pathway when assessed by clonogenic assay, FACS analysis of PI stained cells, and western blot analysis of the cytoplasmic translocation of cytochrome C and the cleavage of caspase-3 and ploy(ADP-ribose) polymerase (PARP) in H1299 human lung cancer cells. GalphasQL up-regulated the Bak expression at the levels of protein and mRNA. Treatment with inhibitors of PKA (H89), SP600125 (JNK inhibitor), and a CRE-decoy blocked GalphasQL-stimulated Bak reporter luciferase activity. Expression of GalphasQL increased basal and gamma ray-induced luciferase activity of cAMP response element binding protein (CREB) and AP-1, and the binding of CREB and AP-1 to Bak promoter. Furthermore, prostaglandin E2, a Galphas activating signal, was found to augment gamma ray-induced apoptosis, which was abolished by treatment with a prostanoid receptor antagonist. These results indicate that Galphas augments gamma ray-induced apoptosis by up-regulation of Bak expression via CREB and AP-1 in H1299 lung cancer cells, suggesting that the efficacy of radiotherapy of lung cancer may be improved by modulating Gs signaling pathway.

Keyword

apoptosis; bcl-2 homologous antagonist-killer protein; cyclic AMP; gamma rays; heterotrimeric GTP-binding protein; receptors, G-protein-coupled

MeSH Terms

Apoptosis/*radiation effects
Cell Line, Tumor
Cyclic AMP Response Element-Binding Protein/metabolism
GTP-Binding Protein alpha Subunits, Gs/*metabolism
*Gamma Rays
Heterotrimeric GTP-Binding Proteins/metabolism
Humans
Lung/*cytology/physiology/radiation effects
Lung Neoplasms
Transcription Factor AP-1/metabolism
*Up-Regulation
bcl-2 Homologous Antagonist-Killer Protein/*metabolism