NUMB maintains bone mass by promoting degradation of PTEN and GLI1 via ubiquitination in osteoblasts.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 30455992.
- Also identified by DOI 10.1038/s41413-018-0030-y and PMC identifier 6226489.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
The adaptor protein NUMB is involved in asymmetric division and cell fate determination and recognized as an antagonist of Notch. Previous studies have proved that Notch activation in osteoblasts contributes to a high bone mass. In this study, however, an osteopenic phenotype was found in 9-week-old mice using osteoblastic specific <i>Col1a1-2.3-Cre</i> to ablate both <i>Numb</i> and its homologue <i>Numbl</i> . The trabecular bone mass decreased dramatically while the cortical bone mass was unaffected. Here, the Notch signal was not activated, while the tensin homologue deleted on human chromosome 10 (PTEN), which dephosphorylates phosphatidylinositide 3-kinases, was elevated, attenuating protein kinase B (Akt). The ubiquitination assay revealed that NUMB may physiologically promote PTEN ubiquitination in the presence of neural precursor cell-expressed developmentally downregulated protein 4-1. In addition, the deficiency of <i>Numb</i>/<i>Numbl</i> also activated the Hedgehog pathway through GLI1. This process was found to improve the ratio of the receptor activator of nuclear factor-kB ligand to osteoprotegerin, which enhanced the differentiation of osteoclasts and bone resorption . In conclusion, this study provides an insight into new functons of NUMB and NUMBL on bone homeostasis.