Growth hormone stimulation of the mitogen-activated protein kinase pathway is cell type specific

The GH receptor is a member of the cytokine receptor superfamily. Studies in the 3T3-F442A mouse preadipocyte have shown that GH activates the Janus kinase (JAK2), the signal transducers and activators of transcription (STAT1, -3, and -5), and mitogen-activated protein (MAP) kinase. Our previous stu...

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Bibliographic Details
Published in:Endocrinology (Philadelphia) 1998-04, Vol.139 (4), p.1965
Main Authors: Love, D W, Whatmore, A J, Clayton, P E, Silva, C M
Format: Article
Language:English
Subjects:
3T3 Cells - enzymology
Adipocytes - enzymology
Animals
Calcium-Calmodulin-Dependent Protein Kinases - metabolism
Cell Line
Enzyme Activation - drug effects
Human Growth Hormone - pharmacology
Humans
Immunosorbent Techniques
Kinetics
Lymphocytes - enzymology
Mice
Phosphorylation
Phosphotyrosine - metabolism
Proto-Oncogene Proteins c-raf - metabolism
Signal Transduction
Tetradecanoylphorbol Acetate - pharmacology
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Summary:The GH receptor is a member of the cytokine receptor superfamily. Studies in the 3T3-F442A mouse preadipocyte have shown that GH activates the Janus kinase (JAK2), the signal transducers and activators of transcription (STAT1, -3, and -5), and mitogen-activated protein (MAP) kinase. Our previous studies in the human IM-9 lymphocyte have shown that GH activates JAK2 and only STAT5 (not STAT1 or -3). In the studies presented here, we have investigated activation of the MAP kinase (MAPK) pathway in the IM-9 lymphocyte. Western blotting with antiphosphotyrosine-, anti-MAPK-, and anti-phospho-MAPK-specific antibodies as well in vitro kinase assays using a synthetic peptide substrate demonstrate that although GH (200 ng/ml) activates MAPK in 3T3-F442A cells (at 5 and 10 min of treatment), it does not activate MAPK in IM-9 lymphocytes at time points ranging from 5-60 min. Nevertheless, the phorbol ester phorbol 12-myristate 13-acetate (50 ng/ml) does activate MAPK in the IM-9 cell, and immunoprecipitation with specific antibodies indicates that this activation occurs through c-Raf-1. Although the 52- and 66-kDa forms of the adapter protein Shc are tyrosine phosphorylated in response to GH treatment in 3T3-F442A cells, we demonstrate that the predominant forms in IM-9 cells are the 52- and 46-kDa forms, and neither is tyrosine phosphorylated in response to GH. These studies further elucidate the differential signaling by GH in two cell types.
ISSN:0013-7227
DOI:10.1210/en.139.4.1965