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Title: Accelerated skeletal development in receptor activity modifying protein 3 knock-out mice and novel insights into calcitonin receptor in primary osteoblasts
Author: Pacharne, Suruchi
ISNI:       0000 0004 5348 9014
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2014
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Receptor activity modifying proteins (RAMPs 1, 2 and 3) a family of single transmembrane accessory proteins, which were discovered for predominantly regulating ligand selectivity and trafficking of G-protein coupled receptors (GPCRs) for the Calcitonin (CT) family of peptides. Calcitonin family of peptides mainly include: Calcitonin (CT), Calcitonin gene related peptide (CGRP), Adrenomedullin (AM) and Amylin (AMY). Functional receptors to these peptides comprise RAMP heterodimers with either Calcitonin receptor (CTR) or Calcitonin like receptor (CLR). Over the last few years, these three isoforms of human RAMPs have been identified to form heterodimers with several other GPCRs. Given the expanding number RAMP-GPCR interactions being identified every year, it is important to understand the role of individual RAMP isoform in both normal and pathological conditions. Since the CT family of peptides are recognized hypocalcaemic peptides that have been studied extensively for developing therapies for low bone mass skeletal disorders, we intended to investigate the role of RAMPs in regulating bone mass. Our pilot study suggested that not RAMP1 but RAMP2 and RAMP3 play an important role in regulating skeletal development. The current work aims to investigate the phenotypic consequence of globally silencing RAMP3 expression in 129/SvEv mice on the skeletal development. Using microCT, dynamic histomorphometry and histology we have demonstrated that RAMP3 KO 129/SvEv mice have anabolic acceleration in skeletal development at an early age that provides protection against age-dependent bone loss. Furthermore, using qPCR and western blotting we have shown that the expression of individual RAMP regulates osteoblasts differentiation and that the in response to the stimulation of PTH, AM and AMY, the expression of RAMPs in RAMP3 KO primary osteoblasts is significantly different to that in WT primary osteoblasts. We have also determined a variant of CTR that responds to AMY stimulation in primary osteoblasts. Additionally our study provides novel insights into role of RAMP3 in regulating the Wnt/β-catenin pathway in primary osteoblasts. This study provides evidence of RAMP3 being an anabolic regulator of skeletal development. Whether this is due to its roles in regulating functions of the CT family of peptides; AM and AMY, or through exerting its effects on other osteotropic hormone receptors that interact with RAMP3 is not yet elucidated. Nevertheless the modulation of RAMP3 function may offer opportunities for anabolic therapies for treating low mass skeletal disorders.
Supervisor: Skerry, Tim Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available