title: Autophagic receptors Nbr1 and p62 coregulate skeletal remodeling.
abstract: Skeletal remodeling is an ongoing process requiring the coordinated action of different cell types to maintain homeostatic control of bone synthesis and degradation. Mutations in p62/SQSTM1 are associated with sporadic and 5q35-linked Paget Disease of Bone (PDB), characterized by focal increased bone turnover. These mutations cluster in the ubiquitin associated (UBA) domain and are thought to lead to enhancement of NFκB pathway activation involved in osteoclastogenesis and hyper-responsiveness to receptor activator of nuclear factorκB ligand (RANKL). The structurally similar selective autophagic receptor, Nbr1, binds to LC3 and p62 and is sequestered into autophagosomes, whereas it accumulates in autophagic-deficient tissues. We have shown that truncation of Nbr1 in a murine model, where it can still interact with p62 but not LC3, leads to increased osteoblast differentiation and activity in vivo. This results in an age-dependent increase in bone mass and bone mineral density. This is a molecular consequence of loss of autophagy receptor function via deletion of its C-terminal UBA domain, and/or modulation of the p38 MAPK cellular signaling pathway.
authors.affiliation: King's College London, Department of Medical and Molecular Genetics, London, England, UK.
authors.forename: Sarah
authors.initials: S
authors.lastname: Waters
authors.forename: Katie
authors.initials: K
authors.lastname: Marchbank
authors.forename: Ellen
authors.initials: E
authors.lastname: Solomon
authors.forename: Caroline A
authors.initials: CA
authors.lastname: Whitehouse
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001343:Autophagy / Q000502:physiology*; D016723:Bone Remodeling / Q000502:physiology*; D001842:Bone and Bones / Q000502:physiology*; D004789:Enzyme Activation; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D009154:Mutation; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D000071456:Sequestosome-1 Protein; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D047908:Intracellular Signaling Peptides and Proteins; C486326:Nbr1 protein, mouse; D011506:Proteins; C099718:SQSTM1 protein, human; D000071456:Sequestosome-1 Protein; D048051:p38 Mitogen-Activated Protein Kinases