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

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 α subunit of Gs (GαsQL) 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. GαsQL 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 GαsQL-stimulated Bak reporter luciferase activity. Expression of GαsQL 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 Gαs activating signal, was found to augment gamma ray-induced apoptosis, which was abolished by treatment with a prostanoid receptor antagonist. These results indicate that Gαs 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.

Differential miRNA expression profiles in proliferating or differentiated keratinocytes in response to gamma irradiation

“…Functional annotation of this list revealed an over-representation of genes involved in the adenylate cyclase G-protein coupled receptor-signaling pathway. The cAMP signaling pathway has been shown to modulate DNA-damaging agents induced apoptosis and DNA repair activity [39,40]. This pathway could be one of the mechanisms downstream to ionizing-radiation-responding miRNAs and necessary for the survival of irradiated cells.…”

Cyclic AMP Suppression Is Sufficient to Induce Gliomagenesis in a Mouse Model of Neurofibromatosis-1

“…However, while cAMP might regulate tumor-promoting functions in these multiple cell types, growth-regulatory effects of cAMP in tumor cells are well described. For example, increased cAMP levels induced p38 phosphorylation and apoptosis in acute promyelocytic leukemia cells (32) and enhanced radiation-induced apoptosis of lung cancer cells through upregulation of Bak (33). Similarly, decreased cAMP inhibited the function and expression of the pro-apoptotic Bcl-2 family member Bim (34, 35).…”

Cyclic AMP Signaling Reduces Sirtuin 6 Expression in Non-small Cell Lung Cancer Cells by Promoting Ubiquitin-Proteasomal Degradation via Inhibition of the Raf-MEK-ERK (Raf/Mitogen-activated Extracellular Signal-regulated Kinase/Extracellular Signal-regulated Kinase) Pathway

“…This in turn regulates the expression of other genes (6). cAMP signaling also modulates cancer cell death induced by anticancer drugs and ␥-rays (7,8).…”