These studies will investigate the molecular mechanisms by which PTH and PTHrP ligands bind to and activate the PTH/PTHrP receptor (PTHR1): The PTHR1 plays vital roles in calcium and phosphate homeostasis, and in bone growth and remodeling. We have new data to suggest that the PTHR1 can adopt different conformations, and that different PTH and PTHrP ligands bind to these conformations with different selectivities, and thus induce different biological responses. Thsu, PTH(1-34) and certain other ligands, but not PTHrP(1-36), bind with high affinity to a novel conformation, called RO, which is insensitive to GTPgammaS, and thus, are not likely coupled to G proteins. Ligands that bind preferentially to RO produce prolonged signaling responses in cells and in animals. We thus hypothesize that RO is a stable intermediary that can convert to active-state, RG. This pedicts that RO-selective ligands will produce prolonged signaling. In contrast, RG-selective ligands will produce short-lived, pulsatile, signaling responses. These hypotheses have important implications, not only for understanding the fundamental mechanisms by which the PTHR1 mediates the biological actions of PTH and PTHrP, endocrine and paracrine, respectively, but also for developing new PTHR1-based therapies for diseases such as osteoporosis and hypoparathyroidism, for which signal duration time appears critical. Our goal is to elucidate the underlying biochemical and cellular mechanisms involved, and to confirm the hypothesis that conformational selectivity at the PTHR1 is biologically relevant, and indeed governs the actions of PTH and PTHrP ligands in vivo. To do this, we will use an integrated experimental design approach that incorporates molecular and pharmacological methods, FRET-based biophysical methods, high-resolution sub-cellular imaging methods, and in vivo mouse model systems. As confirmation of our hypotheses, we will develop and test new PTHR1 ligands that have enhanced conformational selectivity, and thus altered biological and signaling actions. In particular, we will develop new long-acting RO-selective ligands, and assess whether they are superior to PTH(1-34) in normalizing calcium in models of hypoparathyroidism. We also will develop short-acting, RG-selective ligands, and assess whether they have potent anabolic effects on bone with minimal resorptive/calcemic effects. Such agents could represent the """"""""next generation"""""""" of PTHR1 ligands for treating osteoporosis.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Program Projects (P01)
Project #
5P01DK011794-45
Application #
8565023
Study Section
Special Emphasis Panel (ZDK1-GRB-9)
Project Start
Project End
Budget Start
2012-12-01
Budget End
2013-11-30
Support Year
45
Fiscal Year
2013
Total Cost
$333,898
Indirect Cost
$120,561
Name
Massachusetts General Hospital
Department
Type
DUNS #
073130411
City
Boston
State
MA
Country
United States
Zip Code
02199
Bi, Ruiye; Fan, Yi; Lauter, Kelly et al. (2016) Diphtheria Toxin- and GFP-Based Mouse Models of Acquired Hypoparathyroidism and Treatment With a Long-Acting Parathyroid Hormone Analog. J Bone Miner Res 31:975-84
Stevenson, Hilary P; Lin, Guowu; Barnes, Christopher O et al. (2016) Transmission electron microscopy for the evaluation and optimization of crystal growth. Acta Crystallogr D Struct Biol 72:603-15
Ono, Noriaki; Kronenberg, Henry M (2016) Bone repair and stem cells. Curr Opin Genet Dev 40:103-107
Kim, Sang Wan; Lu, Yanhui; Williams, Elizabeth A et al. (2016) Sclerostin Antibody Administration Converts Bone Lining Cells into Active Osteoblasts. J Bone Miner Res :
Wein, Marc N; Liang, Yanke; Goransson, Olga et al. (2016) SIKs control osteocyte responses to parathyroid hormone. Nat Commun 7:13176
Eda, Homare; Santo, Loredana; Wein, Marc N et al. (2016) Regulation of Sclerostin Expression in Multiple Myeloma by Dkk-1: A Potential Therapeutic Strategy for Myeloma Bone Disease. J Bone Miner Res 31:1225-34
Sinha, Partha; Aarnisalo, Piia; Chubb, Rhiannon et al. (2016) Loss of Gsα in the Postnatal Skeleton Leads to Low Bone Mass and a Blunted Response to Anabolic Parathyroid Hormone Therapy. J Biol Chem 291:1631-42
Tenhola, Sirpa; Voutilainen, Raimo; Reyes, Monica et al. (2016) Impaired growth and intracranial calcifications in autosomal dominant hypocalcemia caused by a GNA11 mutation. Eur J Endocrinol 175:211-8
Cheloha, Ross W; Watanabe, Tomoyuki; Dean, Thomas et al. (2016) Backbone Modification of a Parathyroid Hormone Receptor-1 Antagonist/Inverse Agonist. ACS Chem Biol 11:2752-2762
Hattersley, Gary; Dean, Thomas; Corbin, Braden A et al. (2016) Binding Selectivity of Abaloparatide for PTH-Type-1-Receptor Conformations and Effects on Downstream Signaling. Endocrinology 157:141-9

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