The proline-rich region of the GH receptor is essential for JAK2 phosphorylation, activation of cell proliferation, and gene transcription.
Mutational analysis of the proximal transmembrane region of the cytoplasmic domain of the GH receptor (GHR) allowed us to characterize box 1, a proline-rich sequence of eight amino acids, which has been shown to be critical for signal transduction of many cytokine receptors. Mutants of the box 1 region of the rat GHR were studied for their ability to initiate the phosphorylation of JAK2 and the proliferation of stably transfected BAF B03 cells and also the activation of Spi 2.1 gene transcription in transiently transfected Chinese hamster ovary (CHO) cells. Convergence of effects of the box 1 mutants on JAK 2 phosphorylation, cell proliferation, and gene transcription was found. Our results suggest that no single amino acid in the box 1 sequence is essential for signaling and that the last two prolines (PXP motif) and the hydrophobic residues are necessary for integrity of box 1. Box 1 represents a structural determinant, potentially able to provide an interaction between JAK2 and the receptor; this interaction could be direct or indirect via an adaptor protein.
Dinerstein
H
H
INSERM Unité 344-Endocrinologie Moléculaire, Faculté de Médecine Necker Paris, France.
Lago
F
F
Goujon
L
L
Ferrag
F
F
Esposito
N
N
Finidori
J
J
Kelly
P A
PA
Postel-Vinay
M C
MC
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D016466:CHO Cells; D002455:Cell Division; D002460:Cell Line; D006224:Cricetinae; D015870:Gene Expression; D013006:Growth Hormone / Q000378:metabolism; D053614:Janus Kinase 2; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010766:Phosphorylation; D011392:Proline; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins; D011986:Receptors, Somatotropin / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction; D013329:Structure-Activity Relationship; D014158:Transcription, Genetic; D014162:Transfection
D011518:Proto-Oncogene Proteins; D011986:Receptors, Somatotropin; D013006:Growth Hormone; D011392:Proline; D011505:Protein-Tyrosine Kinases; C507927:Jak2 protein, rat; D053614:Janus Kinase 2