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Neighbor of Brca1 gene (Nbr1) functions as a negative regulator of postnatal osteoblastic bone formation and p38 MAPK

Caroline A Whitehouse1, Sarah Waters, Katie Marchbank

  • 1King's College London, Department of Medical and Molecular Genetics, London SE1 9RT, United Kindom. caroline.whitehouse@kcl.ac.uk

Proceedings of the National Academy of Sciences of the United States of America
|July 10, 2010
PubMed

Insights

Genetic truncation of the Neighbor of Brca1 gene (Nbr1) increases bone mass by enhancing osteoblast activity. This occurs through altered p62 levels and p38 MAPK pathway activation, impacting bone remodeling.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Bone Biology

Background:

  • Neighbor of Brca1 gene (Nbr1) acts as an autophagy receptor and scaffold protein.
  • Nbr1 regulates growth-factor receptor and downstream signaling pathways.

Purpose of the Study:

  • Investigate the role of Nbr1 in bone remodeling.
  • Determine the effects of Nbr1 genetic truncation on bone mass and cellular activity.

Main Methods:

  • Utilized murine models with genetic truncation of Nbr1 (Nbr1(tr/tr)).
  • Analyzed bone mass, bone mineral density, osteoblast differentiation, and p38 MAPK pathway activation.
  • Employed co-localization studies with p62 and LC3 in osteoblasts.

Main Results:

  • Nbr1(tr/tr) mice exhibited age-dependent increases in bone mass and density.
  • Truncated Nbr1 failed to complex with activated p38 MAPK, leading to its hyperactivation in osteoblasts and osteoclasts.
  • Pharmacological inhibition of p38 MAPK reversed increased osteoblast differentiation in Nbr1(tr/tr) cells.
  • Nbr1 truncation resulted in increased p62 protein expression.

Conclusions:

  • Nbr1 plays a crucial role in bone remodeling.
  • Loss of Nbr1 function perturbs p62 levels and hyperactivates p38 MAPK, promoting osteoblastogenesis.

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