Growth hormone (GH), derived largely from the anterior pituitary, regulates postnatal growth and metabolism in vertebrates in an endocrine fashion. Recent studies also suggest roles for autocrine-derived GH and for an intact GH axis in formation and behavior of cancers in animals. GH receptor (GHR) is a cell surface glycoprotein cytokine receptor superfamily member that binds GH in its extracellular domain (ECD) and activates signaling via its intracellular domain's (ICD) interaction with the JAK2 tyrosine kinase. Our recent studies of mechanisms regulating GHR availability and activation reveal exciting insights, including: 1) JAK2 association influences GHR surface presentation, stability, and trafficking;2) reducing prolactin receptor (PRLR) levels in human T47D breast cancer cells augments GHR abundance and GH sensitivity;3) novel, conformationally-sensitive anti-GHR ECD antibodies may be useful GH antagonists. We hypothesize: 1) JAK2 expression levels and PRLR expression levels strongly influence GH responsiveness;2) GH-induced GHR conformational changes that underlie GH signaling are potential targets for therapeutic intervention.
Our specific aims are: 1. Determine mechanisms by which JAK2 and PRLR regulate GHR processing, cel surface stability, and downregulation. We will study how GHR predimerization impacts JAK2's modulation of GHR trafficking and the role of GHR ICD tyrosine residues on GH-independent and GH-dependent GHR trafficking. Effects of PRLR expression on GHR availability, GHR-JAK2 association, and GH actions in breast cancer cells will be examined. 2. Determine in vivo efficacy of conformation-specific inhibitory anti-GHR ECD monoclonal antibodies. We will characterize inhibitory properties of two anti-GHR antibodies and Fab fragments in signaling studies, also assessing impact of PRLR expression. We will determine in vivo efficacy of these reagents to antagonize GH signaling and cancer explant growth. These studies probe important determinants of GH sensitivity. Completion will reveal mechanisms regulating cell surface GHR availability and fate and therapeutically relevant tools to modulate GH sensitivity.

Public Health Relevance

Growth hormone is a key regulator of growth and metabolism and recent work suggests that antagonism of growth hormone action may be of therapeutic potential in certain cancers. These studies of the growth hormone receptor investigate the determinants of growth hormone sensitivity at the cellular level. The knowledge gained and the development of inhibitory anti-GH receptor monoclonal antibodies as potential therapeutics may have broad relevance in our understanding of normal physiology and in treatment of cancer.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK058259-12
Application #
8619614
Study Section
Molecular and Cellular Endocrinology Study Section (MCE)
Program Officer
Malozowski, Saul N
Project Start
2011-06-01
Project End
2015-02-28
Budget Start
2014-03-01
Budget End
2015-02-28
Support Year
12
Fiscal Year
2014
Total Cost
$318,638
Indirect Cost
$101,138
Name
University of Alabama Birmingham
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
063690705
City
Birmingham
State
AL
Country
United States
Zip Code
35294
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Zhang, Yue; Wang, Xiangdong; Loesch, Kimberly et al. (2016) TIMP3 Modulates GHR Abundance and GH Sensitivity. Mol Endocrinol 30:587-99
Chen, Hainan; Kleinberger, Jeffrey W; Takane, Karen K et al. (2015) Augmented Stat5 Signaling Bypasses Multiple Impediments to Lactogen-Mediated Proliferation in Human β-Cells. Diabetes 64:3784-97
Liu, Ying; Berry, Philip A; Zhang, Yue et al. (2014) Dynamic analysis of GH receptor conformational changes by split luciferase complementation. Mol Endocrinol 28:1807-19
Zhao, Yueshui; Xiao, Xiaoqiu; Frank, Stuart J et al. (2014) Distinct mechanisms of induction of hepatic growth hormone resistance by endogenous IL-6, TNF-α, and IL-1β. Am J Physiol Endocrinol Metab 307:E186-98
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Gan, Yujun; Buckels, Ashiya; Liu, Ying et al. (2014) Human GH receptor-IGF-1 receptor interaction: implications for GH signaling. Mol Endocrinol 28:1841-54
Gamble, Karen L; Berry, Ryan; Frank, Stuart J et al. (2014) Circadian clock control of endocrine factors. Nat Rev Endocrinol 10:466-75
Corrick, Ryan M; Li, Li; Frank, Stuart J et al. (2013) Hepatic growth hormone resistance after acute injury. Endocrinology 154:1577-88
Xu, Jie; Sun, Dongmei; Jiang, Jing et al. (2013) The role of prolactin receptor in GH signaling in breast cancer cells. Mol Endocrinol 27:266-79

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