title: Pharmacologic modulation of glycogen synthase kinase-3beta promotes p53-dependent apoptosis through a direct Bax-mediated mitochondrial pathway in colorectal cancer cells.
abstract: Activation of p53 tumor suppressor induces either cell cycle arrest or apoptosis through transcription-dependent and independent pathways; however, their relative roles in apoptosis induction and how these pathways are regulated remains elusive. Here, we report a unique role for glycogen synthesis kinase-3beta (GSK-3beta) in regulating p53 functions in human colorectal cancer cells. Pharmacologic modulation of GSK-3beta markedly impaired p53-dependent transactivation of targets including p21 and Puma but promoted p53-dependent conformational activation of Bax, resulting in cytochrome c release, loss of mitochondrial membrane potential, and caspase-9 processing. Thus, p53-mediated damage response is converted from cell cycle arrest to apoptosis following exposure to a variety of chemotherapeutic agents. We found that this effect is associated with the modulation of inhibitory Ser(9) phosphorylation of GSK-3beta but not with the activating tyrosine phosphorylation. We further show that the induction of apoptosis is through a direct mitochondrial pathway that requires Bax but not Puma. Our results underscore the importance of transcription-independent mechanism in p53-induced apoptosis and indicate that GSK-3beta plays distinct dual roles in regulating p53 pathways: promoting p53 transcriptional activity in the nucleus but suppressing p53-mediated direct apoptotic function at the mitochondria. Importantly, our data suggest that small-molecule inhibition of GSK-3beta might represent a novel approach for modulating chemotherapy.
authors.affiliation: Laboratory of Molecular Pharmacology, Genome Institute of Singapore, Singapore, Singapore.
authors.forename: Jing
authors.initials: J
authors.lastname: Tan
authors.forename: Li
authors.initials: L
authors.lastname: Zhuang
authors.forename: Hui-Sun
authors.initials: HS
authors.lastname: Leong
authors.forename: N Gopalakrishna
authors.initials: NG
authors.lastname: Iyer
authors.forename: Edison T
authors.initials: ET
authors.lastname: Liu
authors.forename: Qiang
authors.initials: Q
authors.lastname: Yu
mesh_terms: D000627:Aminophenols / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D051017:Apoptosis Regulatory Proteins / Q000502:physiology; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors* / Q000378:metabolism / Q000502:physiology; D000071679:Glycogen Synthase Kinase 3 beta; D045325:HCT116 Cells; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D008301:Maleimides / Q000494:pharmacology; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology*; D011487:Protein Conformation; D011518:Proto-Oncogene Proteins / Q000502:physiology; D034622:RNA Interference; D015533:Transcriptional Activation / Q000187:drug effects / Q000502:physiology; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D051028:bcl-2-Associated X Protein / Q000502:physiology*
chemical_list: C417520:3-(3-chloro-4-hydroxyphenylamino)-4-(4-nitrophenyl)-1H-pyrrole-2,5-dione; D000627:Aminophenols; D051017:Apoptosis Regulatory Proteins; C494826:BAX protein, human; C438378:BBC3 protein, human; D004791:Enzyme Inhibitors; D007211:Indoles; D008301:Maleimides; D011518:Proto-Oncogene Proteins; C417521:SB 216763; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D038362:Glycogen Synthase Kinase 3