title: Requirement for phosphoinositide 3-OH kinase in growth hormone signalling to the mitogen-activated protein kinase and p70s6k pathways.
abstract: Pituitary growth hormone (GH) co-ordinately stimulates three distinct signalling pathways in 3T3-F442A preadipocytes, the STAT (signal transducer and activator of transcription) pathway, the mitogen-activated protein (MAP) kinase cascade and p70s6k. The mechanisms linking the GH receptor to these signals have not been fully identified. In this study we have examined the role of phosphoinositide 3-OH kinase (PI 3-kinase). Pretreatment of cells with wortmannin, a specific inhibitor of PI 3-kinase, prevented the activation of p70s6k and partially inhibited the activation of p42 and p44 MAP kinases by GH. In contrast, wortmannin failed to appreciably affect the GH-stimulated tyrosyl phosphorylation of JAK-2 or STAT-1. GH transiently increased the activity of PI 3-kinase recovered in antiphosphotyrosine immunoprecipitates. In addition, several tyrosyl-phosphorylated proteins were specifically adsorbed from lysates of cells exposed to GH by a glutathione S-transferase fusion protein containing the 85 kDa regulatory subunit of PI 3-kinase. GH also induced an increase in the PI 3-kinase activity associated with both JAK-2 and insulin receptor substrate-1 (IRS-1) immunoprecipitates. These results establish PI 3-kinase as an important mediator of GH signalling to the MAP kinase and p70s6k pathways and suggest that PI 3-kinase is activated by a mechanism involving JAK-2 and IRS-1.
authors.affiliation: Hannah Research Institute, Scotland, U.K.
authors.forename: E
authors.initials: E
authors.lastname: Kilgour
authors.forename: I
authors.initials: I
authors.lastname: Gout
authors.forename: N G
authors.initials: NG
authors.lastname: Anderson
mesh_terms: D016475:3T3 Cells; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D013006:Growth Hormone / Q000378:metabolism*; D055504:Insulin Receptor Substrate Proteins; D053614:Janus Kinase 2; D051379:Mice; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019000:Phosphotyrosine / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins; D019893:Ribosomal Protein S6 Kinases; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D004791:Enzyme Inhibitors; D013006:Growth Hormone; D055504:Insulin Receptor Substrate Proteins; D053614:Janus Kinase 2; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins; D017853:Phosphotransferases (Alcohol Group Acceptor); D019000:Phosphotyrosine; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases; D011518:Proto-Oncogene Proteins; D019893:Ribosomal Protein S6 Kinases; D000077191:Wortmannin; C526295:Irs1 protein, mouse; C507926:Jak2 protein, mouse