Growth Hormone-dependent Differentiation of 3T3-F442A Preadipocytes Requires Janus Kinase/Signal Transducer and Activator of Transcription but Not Mitogen-activated Protein Kinase or p70 S6 Kinase Signaling

• Published in: The Journal of biological chemistry 1999-03, Vol.274 (13), p.8662-8668
• Main Authors: Yarwood, S J, Sale, E M, Sale, G J, Houslay, M D, Kilgour, E, Anderson, N G
• Format: Article
• Language: English
• Subjects: 3T3 Cells; Animals; Calcium-Calmodulin-Dependent Protein Kinases - metabolism; Cell Differentiation - drug effects; DNA-Binding Proteins - metabolism; Enzyme Activation; Epidermal Growth Factor - pharmacology; Flavonoids - pharmacology; Growth Hormone - pharmacology; Insulin - pharmacology; Janus Kinase 2; Mice; Milk Proteins; Mitogen-Activated Protein Kinase 1 - metabolism; Mitogen-Activated Protein Kinase 3; Mitogen-Activated Protein Kinases; Oligonucleotides, Antisense - genetics; Oligonucleotides, Antisense - pharmacology; Protein-Tyrosine Kinases - metabolism; Proto-Oncogene Proteins; Ribosomal Protein S6 Kinases - metabolism; Signal Transduction; Sirolimus - pharmacology; STAT5 Transcription Factor; Trans-Activators - metabolism; Transcriptional Activation - genetics; Triiodothyronine - pharmacology
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.274.13.8662

The signals mediating growth hormone (GH)-dependent differentiation of 3T3-F442A preadipocytes under serum-free conditions have been studied. GH priming of cells was required before the induction of terminal differentiation by a combination of epidermal growth factor, tri-iodothyronine, and insulin. Cellular depletion of Janus kinase-2 (JAK-2) using antisense oligodeoxynucleotides (ODNs) prevented GH-stimulated JAK-2 and signal transducer and activator of transcription (STAT)-5 tyrosine phosphorylation and severely attenuated the ability of GH to promote differentiation. Although p42 MAPK /p44 MAPK mitogen-activated protein kinases were activated during GH priming, treatment of cells with PD 098059, which prevented activation of these kinases, did not block GH priming. However, antisense ODN-mediated depletion of mitogen-activated protein kinases from the cells showed that their expression was necessary for terminal differentiation. Similarly, although p70 s6k was activated during GH priming, pretreatment of cells with rapamycin, which prevented the activation of p70 s6k , had no effect on GH priming. However, rapamycin did partially block epidermal growth factor, tri-iodothyronine, and insulin-stimulated terminal differentiation. By contrast, cellular depletion of STAT-5 with antisense ODNs completely abolished the ability of GH to promote differentiation. These results indicate that JAK-2, acting specifically via STAT-5, is necessary for GH-dependent differentiation of 3T3-F442A preadipocytes. Activation of p42 MAPK /p44 MAPK and p70 s6k is not essential for the promotion of differentiation by GH, although these signals are required for GH-independent terminal differentiation.