title: Loss of Cbl-PI3K interaction modulates the periosteal response to fracture by enhancing osteogenic commitment and differentiation.
abstract: The periosteum contains multipotent skeletal progenitors that contribute to bone repair. The signaling pathways regulating the response of periosteal cells to fracture are largely unknown. Phosphatidylinositol-3 Kinase (PI3K), a prominent lipid kinase, is a major signaling protein downstream of several factors that regulate osteoblast differentiation. Cbl is an E3 ubiquitin ligase and a major adaptor protein that binds to the p85 regulatory subunit and modulates PI3K activity. Substitution of tyrosine 737 to phenylalanine (Y737F) in Cbl abolishes the interaction between Cbl and p85 subunit without affecting the Cbl's ubiquitin ligase function. Here, we investigated the role of PI3K signaling during the very early stages of fracture healing using OsterixRFPreporter mice. We found that the absence of PI3K regulation by Cbl resulted in robust periosteal thickening, with increased proliferation of periosteal cells. While the multipotent properties of periosteal progenitors to differentiate into chondrocytes and adipocytes did not change, osteogenic differentiation in the absence of Cbl-PI3K interaction was highly augmented. The increased stability and nuclear localization of Osterix observed in periosteal cells lacking Cbl-PI3K interaction may explain this enhanced osteogenic differentiation since the expression of Osterix transcriptional target genes including osteocalcin and BSP are increased in YF cells. Overall, our findings highlight a hitherto unexplored and novel role for Cbl and PI3K in modulating the osteogenic response of periosteal cells during the early stages of fracture repair.
authors.affiliation: Department of Orthopaedic Surgery, United States.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Scanlon
authors.affiliation: Department of Orthopaedic Surgery, United States; Department of Genetics and Genome Sciences, United States.
authors.forename: Bhavita
authors.initials: B
authors.lastname: Walia
authors.affiliation: Department of Orthopaedic Surgery, United States.
authors.forename: Jungeun
authors.initials: J
authors.lastname: Yu
authors.affiliation: Department of Genetics and Genome Sciences, United States; Center for Molecular Medicine, United States.
authors.forename: Marc
authors.initials: M
authors.lastname: Hansen
authors.affiliation: Department of Orthopaedic Surgery, United States; Department of Genetics and Genome Sciences, United States.
authors.forename: Hicham
authors.initials: H
authors.lastname: Drissi
authors.affiliation: Department of Reconstructive Sciences, UConn Health, Farmington, CT, United States.
authors.forename: Peter
authors.initials: P
authors.lastname: Maye
authors.affiliation: Department of Orthopaedic Surgery, United States; Department of Genetics and Genome Sciences, United States. Electronic address: asanjay@uchc.edu.
authors.forename: Archana
authors.initials: A
authors.lastname: Sanjay
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D002452:Cell Count; D002454:Cell Differentiation; D019070:Cell Lineage; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation; D017102:Fracture Healing; D050723:Fractures, Bone / Q000473:pathology*; D008648:Mesoderm / Q000473:pathology; D008810:Mice, Inbred C57BL; D009154:Mutation / Q000235:genetics; D010012:Osteogenesis; D010521:Periosteum / Q000473:pathology*; D058539:Phosphatidylinositol 3-Kinase / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D050721:Proto-Oncogene Proteins c-cbl / Q000378:metabolism*; D000076182:Sp7 Transcription Factor / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D015415:Biomarkers; D000076182:Sp7 Transcription Factor; C479466:Sp7 protein, mouse; D050721:Proto-Oncogene Proteins c-cbl; D058539:Phosphatidylinositol 3-Kinase; D051057:Proto-Oncogene Proteins c-akt; D000469:Alkaline Phosphatase
keywords: Alkaline Phosphatase activity; Fracture; Laser capture microdissection; Osterix; PI3K; Periosteum