Conformational changes required in the human growth hormone receptor for growth hormone signaling.
Growth hormone (GH) plays a significant role in normal growth and development. Signaling to the cell is believed to require growth hormone receptor (GHR) dimerization, which occurs following binding of a single growth hormone molecule to each of two receptors. We have developed human growth hormone receptor-specific monoclonal antibodies, one of which was used here to characterize hormone/receptor interactions. This antibody, GHR05, is directed against the hinge spanning subdomains I and II of the receptor's extracellular region. Antibody binding to the cell surface receptor increases upon receptor binding to growth hormone, but not when it binds a mutant form, hGHG120R, which does not trigger receptor activation. Growth hormone binding thus appears to lead to a conformational change in the receptor epitope recognized by GHR05, giving rise to the active dimer configuration, necessary for signal transduction. Using a chimeric receptor-expressing, growth hormone-dependent murine cell line, we find that GHR05 binds to the receptor in the absence of human GH and delivers a signal leading to cell proliferation. Finally, GHR05 treatment of IM-9 cells, a human cell line expressing a functional human GHR, leads to cell proliferation mediated by the generation of GH-specific signals, including phosphorylation of the JAK2 tyrosine kinase and activation of STAT5.
Mellado
M
M
Department of Immunology and Oncology, Centro Nacional de Biotecnología, CSIC, Campus de Cantoblanco, E-28049 Madrid, Spain. mmellado@cnb.vam.es
Rodríguez-Frade
J M
JM
Kremer
L
L
von Kobbe
C
C
de Ana
A M
AM
Mérida
I
I
Martinez-A
C
C
D000818:Animals; D000911:Antibodies, Monoclonal; D002453:Cell Cycle; D002455:Cell Division; D004268:DNA-Binding Proteins / Q000378:metabolism; D000939:Epitopes / Q000378:metabolism; D019382:Human Growth Hormone / Q000378:metabolism*; D006801:Humans; D053614:Janus Kinase 2; D051379:Mice; D008894:Milk Proteins; D008954:Models, Biological; D011487:Protein Conformation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D011986:Receptors, Somatotropin / Q000737:chemistry* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D050799:STAT5 Transcription Factor; D015398:Signal Transduction; D013329:Structure-Activity Relationship; D015534:Trans-Activators / Q000378:metabolism
D000911:Antibodies, Monoclonal; D004268:DNA-Binding Proteins; D000939:Epitopes; D008894:Milk Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011986:Receptors, Somatotropin; D011993:Recombinant Fusion Proteins; D050799:STAT5 Transcription Factor; D015534:Trans-Activators; D019382:Human Growth Hormone; D011505:Protein-Tyrosine Kinases; C507924:JAK2 protein, human; C507926:Jak2 protein, mouse; D053614:Janus Kinase 2