Growth hormone (GH) has long been known to be an important determinant of body growth. It has also gained much attention lately because of its potential clinical applications in reversing metabolic correlates of aging and disease. As the clinical and therapeutic potential of GH becomes apparent, it is clear that a more mechanistic appreciation of GH action is needed. The present studies will test the hypothesis that activation by GH of a GH receptor (GHR)-associated tyrosine kinase is an important component of the GHR signal transduction pathway. Two lines of evidence now strongly suggest that GHR forms a dissociable complex with a tyrosine kinase rather than having intrinsic tyrosine kinase activity. First, GH-GHR complexes from cells expressing cloned liver GHR (which does not have a consensus sequence for an ATP binding site) co-purify with and are phosphorylated by a tyrosine kinase. The amount of tyrosine kinase available appears to be cell-type specific. Second, tyrosine kinase activity can be dissociated from, and then reconstituted with, GHR. These preliminary results shall be verified and the GHR-kinase identified by size. The important mechanistic question of whether GH binding to GHR increases the association of GHR with GHR-kinase and/or increases the activity of the GHR-kinase will be addressed. Using antibodies to known tyrosine kinases, it will be determined whether the GHR is a known kinase (e.g. Src family). If it cannot be established that the GHR-kinase is a known kinase, experiments will be initiated to clone the GHR kinase. Expression libraries will be screened for proteins that bind to GHR cytoplasmic domain, or portions thereof. If larger amounts of the GHR-kinase are required for identification or cloning, GHR affinity columns will be used to affinity purify GHR-kinase. GHR will be obtained by overexpressing cloned liver GHR in a baculovirus system, or the cytoplasmic domain of GHR in E. coli if the GHR-cytoplasmic domain is shown to associate with GHR-kinase when expressed as a dominant negative mutant. The importance of tyrosine kinase activity in actions of GH will be examined by testing whether inhibitors of the GHR-kinase cause loss of specific functions of GH. The effect of mutating specific GHR tyrosyl residues on specific functions of GH will be tested to evaluate the importance of GHR tyrosyl phosphorylation itself. Substrates of the GHR-kinase, and proteins whose association with GHR may be affected by phosphorylation of GHR tyrosyl residues, will also be identified and characterized. These studies will provide greatly needed insight into the complex mechanism by which GH brings about its diverse effects.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Research Project (R01)
Project #
Application #
Study Section
Endocrinology Study Section (END)
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Michigan Ann Arbor
Schools of Medicine
Ann Arbor
United States
Zip Code
O'Leary, Erin E; Mazurkiewicz-Muñoz, Anna M; Argetsinger, Lawrence S et al. (2013) Identification of steroid-sensitive gene-1/Ccdc80 as a JAK2-binding protein. Mol Endocrinol 27:619-34
Ray, Bridgette N; Kweon, Hye Kyong; Argetsinger, Lawrence S et al. (2012) Research resource: identification of novel growth hormone-regulated phosphorylation sites by quantitative phosphoproteomics. Mol Endocrinol 26:1056-73
Maures, Travis J; Su, Hsiao-Wen; Argetsinger, Lawrence S et al. (2011) Phosphorylation controls a dual-function polybasic nuclear localization sequence in the adapter protein SH2B1? to regulate its cellular function and distribution. J Cell Sci 124:1542-52
Cui, Tracy X; Lin, Grace; LaPensee, Christopher R et al. (2011) C/EBP? mediates growth hormone-regulated expression of multiple target genes. Mol Endocrinol 25:681-93
Argetsinger, Lawrence S; Stuckey, Jeanne A; Robertson, Scott A et al. (2010) Tyrosines 868, 966, and 972 in the kinase domain of JAK2 are autophosphorylated and required for maximal JAK2 kinase activity. Mol Endocrinol 24:1062-76
Robertson, Scott A; Koleva, Rositsa I; Argetsinger, Lawrence S et al. (2009) Regulation of Jak2 function by phosphorylation of Tyr317 and Tyr637 during cytokine signaling. Mol Cell Biol 29:3367-78
Thompson, Brian R; Mazurkiewicz-Muñoz, Anna M; Suttles, Jill et al. (2009) Interaction of adipocyte fatty acid-binding protein (AFABP) and JAK2: AFABP/aP2 as a regulator of JAK2 signaling. J Biol Chem 284:13473-80
Jin, Hui; Lanning, Nathan J; Carter-Su, Christin (2008) JAK2, but not Src family kinases, is required for STAT, ERK, and Akt signaling in response to growth hormone in preadipocytes and hepatoma cells. Mol Endocrinol 22:1825-41
Li, Zhiqin; Zhou, Yingjiang; Carter-Su, Christin et al. (2007) SH2B1 enhances leptin signaling by both Janus kinase 2 Tyr813 phosphorylation-dependent and -independent mechanisms. Mol Endocrinol 21:2270-81
Kurzer, Jason H; Saharinen, Pipsa; Silvennoinen, Olli et al. (2006) Binding of SH2-B family members within a potential negative regulatory region maintains JAK2 in an active state. Mol Cell Biol 26:6381-94

Showing the most recent 10 out of 63 publications