Targeted overexpression of G protein-coupled receptor kinase-2 in osteoblasts promotes bone loss.

Published

Journal Article

To investigate the role of G protein-coupled receptor kinases (GRKs) in regulating bone formation in vivo, we overexpressed the potent G protein-coupled receptor (GPCR) regulator GRK2 in osteoblasts, using the osteocalcin gene-2 promoter to target expression to osteoblastic cells. Using the parathyroid hormone (PTH) receptor as a model system, we found that overexpression of GRK2 in osteoblasts attenuated PTH-induced cAMP generation by mouse calvaria ex vivo. This decrease in GPCR responsiveness was associated with a reduction in bone mineral density (BMD) in transgenic (TG) mice compared with non-TG littermate controls. The decrease in BMD was most prominent in trabecular-rich lumbar spine and was not observed in cortical bone of the femoral shaft. Quantitative computed tomography indicated that the loss of trabecular bone was due to a decrease in trabecular thickness, with little change in trabecular number. Histomorphometric analyses confirmed the decrease in trabecular bone volume and demonstrated reduced bone remodeling, as evidenced by a decrease in osteoblast numbers and osteoblast-mediated bone formation. Osteoclastic activity also appeared to be reduced because urinary excretion of the osteoclastic activity marker deoxypyridinoline was decreased in TG mice compared with control animals. Consistent with reduced coupling of osteoblast-mediated bone formation to osteoclastic bone resorption, mRNA levels of both osteoprotegrin and receptor activator of NF-kappaB ligand were altered in calvaria of TG mice in a pattern that would promote a low rate of bone remodeling. Taken together, these data suggest that enhancing GRK2 activity and consequently reducing GPCR activity in osteoblasts produces a low bone-turnover state that reduces bone mass.

Full Text

Duke Authors

Cited Authors

  • Wang, L; Liu, S; Quarles, LD; Spurney, RF

Published Date

  • April 2005

Published In

Volume / Issue

  • 288 / 4

Start / End Page

  • E826 - E834

PubMed ID

  • 15585587

Pubmed Central ID

  • 15585587

Electronic International Standard Serial Number (EISSN)

  • 1522-1555

International Standard Serial Number (ISSN)

  • 0193-1849

Digital Object Identifier (DOI)

  • 10.1152/ajpendo.00422.2004

Language

  • eng