PKC alpha-dependent regulation of the IGF1 receptor in adult and embryonic rat cardiomyocytes.
In both, the adult rat ventricular cardiomyocytes and the embryonic rat heart cell line, H9c2, acute exposure to IGF1 resulted in activation of the IGF1 receptor's internal tyrosine kinase, and this was completely blocked by the PKC alpha inhibitor, Gö6976. In addition, RNA interference using siRNA mediated gene silencing of PKC alpha-inhibited IGF1 receptor activity and blocked PKC alpha expression in H9c2 cells. Biochemical experiments demonstrate that PKC alpha is associated with the IGFlR (beta subunit) only after acute IGF1 exposure, and this may suggest that there is a direct interaction and possibly a PKC alpha phosphorylation site within the internal IGF1 receptor domain. The downstream effects of blocking PKC alpha activity by exposure to Gö6976 include inhibition of IGF1-stimuated PI3 kinase activity and reduced IGF1-stimulated c-fos expression in the adult cardiomyocytes. Previously, the laboratory has reported that IGF1 activates PKC alpha in adult rat cardiomyocytes, and that PKC alpha activity is required for IGF1-dependent Erk/Erk2 activity and protein synthesis. Here, it is shown that IGF1-dependent protein synthesis is completely blocked by PD98059, indicating that the Raf-Mek-Erk cascade is required for IGF1's anabolic activity. Pretreatment with LY294002, a specific inhibitor of PI3 kinase, blocked IGF1-stimulated Erk1/Erk2 activity; therefore, PI3 kinase may also be required for IGF1-dependent protein synthesis. In H9c2 cells, coincubation with PMA lead to an increase in the rate of the IGF1 receptor activation, and this may further implicate a role for PKC in regulating the IGF1R. In conclusion, PKC alpha plays an essential role in the IGF1-signaling cascade, including the regulation of key signaling proteins involved in cell signaling and gene expression, and this may primarily be due to PKC alpha directly regulating the IGF1R.
Maniar
Ruchita
R
Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, 1020 Locust Street, Philadelphia, PA 19107, USA.
Pecherskaya
Anna
A
Ila
Richard
R
Solem
Michele
M
D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D002460:Cell Line; D002478:Cells, Cultured; D004622:Embryo, Mammalian; D004789:Enzyme Activation / Q000187:drug effects; D005419:Flavonoids / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic; D006352:Heart Ventricles / Q000166:cytology; D007211:Indoles / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D007700:Kinetics; D008297:Male; D008301:Maleimides / Q000494:pharmacology; D019950:Mitogen-Activated Protein Kinase 1 / Q000032:analysis / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000032:analysis / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation; D014176:Protein Biosynthesis / Q000187:drug effects; D051571:Protein Kinase C-alpha / Q000037:antagonists & inhibitors / Q000378:metabolism*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017526:Receptor, IGF Type 1 / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D005419:Flavonoids; D007211:Indoles; D008301:Maleimides; D034741:RNA, Small Interfering; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1; D051571:Protein Kinase C-alpha; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; C088060:bisindolylmaleimide; D013755:Tetradecanoylphorbol Acetate; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one