title: TGF beta receptor II interacting protein-1, an intracellular protein has an extracellular role as a modulator of matrix mineralization.
abstract: Transforming growth factor beta receptor II interacting protein 1 (TRIP-1), a predominantly intracellular protein is localized in the ECM of bone. TRIP-1 lacks a signal peptide, therefore, in this study, we provide evidence that intracellular TRIP-1 can be packaged and exported to the ECM via exosomes. Overexpression of TRIP-1 in MC3T3-E1 cells resulted in increased matrix mineralization during differentiation and knockdown resulted in reduced effects. In vivo function of TRIP-1 was studied by an implantation assay performed using TRIP-1 overexpressing and knockdown cells cultured in a 3-dimmensional scaffold. After 4 weeks, the subcutaneous tissues from TRIP-1 overexpressing cells showed higher calcium and phosphate deposits, arranged collagen fibrils and increased expression of Runx2 and alkaline phosphatase. Nucleation studies on demineralized and deproteinized dentin wafer is a powerful tool to determine the functional role of noncollagenous proteins in matrix mineralization. Using this system, we provide evidence that TRIP-1 binds to Type-I collagen and can promote mineralization. Surface plasmon resonance analysis demonstrated that TRIP-1 binds to collagen with KD= 48 μM. SEM and TEM analysis showed that TRIP-1 promoted the nucleation and growth of calcium phosphate mineral aggregates. Taken together, we provide mechanistic insights of this intracellular protein in matrix mineralization.
authors.affiliation: Brodie Tooth Development Genetics &Regenerative Medicine Research Laboratory, Department of Oral Biology, University of Illinois at Chicago, Chicago, Il 60612, USA.
authors.forename: Amsaveni
authors.initials: A
authors.lastname: Ramachandran
authors.affiliation: Brodie Tooth Development Genetics &Regenerative Medicine Research Laboratory, Department of Oral Biology, University of Illinois at Chicago, Chicago, Il 60612, USA.
authors.forename: Sriram
authors.initials: S
authors.lastname: Ravindran
authors.affiliation: Brodie Tooth Development Genetics &Regenerative Medicine Research Laboratory, Department of Oral Biology, University of Illinois at Chicago, Chicago, Il 60612, USA.
authors.forename: Chun-Chieh
authors.initials: CC
authors.lastname: Huang
authors.affiliation: Brodie Tooth Development Genetics &Regenerative Medicine Research Laboratory, Department of Oral Biology, University of Illinois at Chicago, Chicago, Il 60612, USA.
authors.forename: Anne
authors.initials: A
authors.lastname: George
mesh_terms: D000818:Animals; D002113:Calcification, Physiologic / Q000502:physiology*; D002130:Calcium Phosphates / Q000378:metabolism; D002454:Cell Differentiation / Q000235:genetics; D002460:Cell Line; D024042:Collagen Type I / Q000378:metabolism; D039621:Eukaryotic Initiation Factor-3 / Q000378:metabolism; D039642:Eukaryotic Initiation Factors / Q000235:genetics / Q000378:metabolism*; D055354:Exosomes / Q000378:metabolism; D005109:Extracellular Matrix / Q000502:physiology*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D008297:Male; D008819:Mice, Nude; D010006:Osteoblasts / Q000378:metabolism* / Q000502:physiology; D010012:Osteogenesis / Q000235:genetics; D051381:Rats; D012886:Skull / Q000166:cytology
chemical_list: D002130:Calcium Phosphates; D024042:Collagen Type I; D039621:Eukaryotic Initiation Factor-3; D039642:Eukaryotic Initiation Factors; D047908:Intracellular Signaling Peptides and Proteins; C576121:TRIP-1 protein, mouse; C576123:TRIP-1 protein, rat; C096013:EIF3I protein, human; C020243:calcium phosphate