title: Localization of transforming growth factor beta receptor II interacting protein-1 in bone and teeth: implications in matrix mineralization.
abstract: Transforming growth factor beta receptor II (TGFβR-II) interacting protein 1 (TRIP-1) is a WD-40 protein that binds to the cytoplasmic domain of the TGF-β type II receptor in a kinase-dependent manner. To investigate the role of TRIP-1 in mineralized tissues, we examined its pattern of expression in cartilage, bone, and teeth and analyzed the relationship between TRIP-1 overexpression and mineralized matrix formation. Results demonstrate that TRIP-1 was predominantly expressed by osteoblasts, odontoblasts, and chondrocytes in these tissues. Interestingly, TRIP-1 was also localized in the extracellular matrix of bone and at the mineralization front in dentin, suggesting that TRIP-1 is secreted by nonclassical secretory mechanisms, as it is devoid of a signal peptide. In vitro nucleation studies demonstrate a role for TRIP-1 in nucleating calcium phosphate polymorphs. Overexpression of TRIP-1 favored osteoblast differentiation of undifferentiated mesenchymal cells with an increase in mineralized matrix formation. These data indicate an unexpected role for TRIP-1 during development of bone, teeth, and cartilage.
authors.affiliation: Brodie Tooth Development Genetics & Regenerative Medicine Research Laboratory, Department of Oral Biology, University of Illinois at Chicago, Chicago, Illinois, USA.
authors.forename: Amsaveni
authors.initials: A
authors.lastname: Ramachandran
authors.forename: Sriram
authors.initials: S
authors.lastname: Ravindran
authors.forename: Anne
authors.initials: A
authors.lastname: George
mesh_terms: D001842:Bone and Bones / Q000378:metabolism*; D002113:Calcification, Physiologic; D002460:Cell Line; D039621:Eukaryotic Initiation Factor-3 / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D014070:Tooth / Q000378:metabolism*
chemical_list: D039621:Eukaryotic Initiation Factor-3; C096013:EIF3I protein, human