Growth hormone, but not insulin, activates STAT5 proteins in adipocytes in vitro and in vivo.
STAT 5 proteins are latent transcription factors which have been shown to be activated by growth hormone (GH) in many cell types. However, some recent studies also suggest that STAT 5B is a physiological substrate of the insulin receptor. In our studies, we have shown that physiological levels of insulin do not induce STAT 5 tyrosine phosphorylation or affect the nuclear distribution of STATs 5A or 5B in 3T3-L1 adipocytes. Moreover, we did not observe the activation of STAT 5 in the adipose tissue or skeletal muscle of mice following an acute intraperitoneal injection of insulin. However, acute GH administration, both in vitro and in vivo, resulted in the activation of STAT 5 proteins. In summary, our results indicate that STAT 5 proteins are not activated by physiological levels of insulin in adipose tissue.
Zvonic
Sanjin
S
Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
Story
David J
DJ
Stephens
Jacqueline M
JM
Mynatt
Randall L
RL
D016475:3T3 Cells; D017667:Adipocytes / Q000187:drug effects* / Q000378:metabolism; D000818:Animals; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004789:Enzyme Activation; D013006:Growth Hormone / Q000494:pharmacology*; D007328:Insulin / Q000494:pharmacology*; D051379:Mice; D008894:Milk Proteins; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010766:Phosphorylation; D050799:STAT5 Transcription Factor; D015534:Trans-Activators / Q000378:metabolism*
D004268:DNA-Binding Proteins; D007328:Insulin; D008894:Milk Proteins; D050799:STAT5 Transcription Factor; D015534:Trans-Activators; D013006:Growth Hormone; D020928:Mitogen-Activated Protein Kinases