title: Enhancement of AG1024-induced H9c2 cardiomyoblast cell apoptosis via the interaction of IGF2R with Galpha proteins and its downstream PKA and PLC-beta modulators by IGF-II.
abstract: Our previous studies found that insulin-like growth factor-I receptor (IGF1R) signaling blockade caused cardiac hypertrophy, and that apoptosis is required for upregulating the IGF-II and the IGF-II/ mannose 6-phosphate receptor (IGF2R) gene. However, the role of IGF-II in the regulation of cell apoptosis through IGF2R is little known. In this study, we hypothesized that IGF-II may induce cell apoptosis through IGF2R but is dependent on IGF1R activity. Western blots and TUNEL assay revealed that in the presence of IGF1R, exogenous IGF-II acts, like IGF-I, would increase phospho-Akt through IGF1R, but does not affect the caspase 3 activation and apoptotic induction in H9c2 cardiomyoblast cells. Conversely, AG1024, an inhibitor of IGF1R activity, causes cell apoptosis, and the treatment with IGF-II further enhances this process, implying that it occurs through IGF2R. Moreover, immunoprecipitation assay revealed that treatment with IGF-II could enhance the interaction of IGF2R with Galphai and Galphaq but reduce its binding with Galphas, resulting in the reduction of phospho-PKA and the activation of PLC-beta. Taken together, these data provide new insight into the dual role of IGF-II in the control of IGF1R dependent cell apoptosis and involved activation of IGF2R signaling. Improving IGF1R activity and suppressing IGF2R may be a good strategy to prevent the progression of heart disease with cardiomyocyte apoptosis.
authors.affiliation: Institute of Biochemistry and Biotechnology, Chung Shan Medical University, Taichung 402, Taiwan, Republic of China.
authors.forename: Chun-Hsien
authors.initials: CH
authors.lastname: Chu
authors.forename: Chih-Yang
authors.initials: CY
authors.lastname: Huang
authors.forename: Ming-Chin
authors.initials: MC
authors.lastname: Lu
authors.forename: James A
authors.initials: JA
authors.lastname: Lin
authors.forename: Fuu-Jen
authors.initials: FJ
authors.lastname: Tsai
authors.forename: Chang-Hai
authors.initials: CH
authors.lastname: Tsai
authors.forename: Chia-Yih
authors.initials: CY
authors.lastname: Chu
authors.forename: Wu-Hsien
authors.initials: WH
authors.lastname: Kuo
authors.forename: Li-Mien
authors.initials: LM
authors.lastname: Chen
authors.forename: Ling-Yun
authors.initials: LY
authors.lastname: Chen
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D053148:Caspase 3 / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D044385:GTP-Binding Protein alpha Subunits / Q000378:metabolism*; D006331:Heart Diseases / Q000378:metabolism / Q000473:pathology; D006801:Humans; D007335:Insulin-Like Growth Factor II / Q000378:metabolism* / Q000494:pharmacology; D032386:Myoblasts, Cardiac / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects / Q000502:physiology; D011493:Protein Kinase C / Q000378:metabolism; D064546:Protein Kinase C beta; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D017526:Receptor, IGF Type 1 / Q000378:metabolism; D017527:Receptor, IGF Type 2 / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D020032:Tyrphostins / Q000494:pharmacology*
chemical_list: D044385:GTP-Binding Protein alpha Subunits; D017527:Receptor, IGF Type 2; D020032:Tyrphostins; C447031:tyrphostin AG 1024; D007335:Insulin-Like Growth Factor II; D017526:Receptor, IGF Type 1; D051057:Proto-Oncogene Proteins c-akt; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D064546:Protein Kinase C beta; C505410:Casp3 protein, rat; D053148:Caspase 3