title: Expression and distribution of grp-78/bip in mineralizing tissues and mesenchymal cells.
abstract: Glucose-regulated protein 78 (GRP-78) is one of the many endoplasmic reticulum chaperone proteins that have been shown to possess multifunctional roles. We have previously demonstrated that GRP-78 functions as a receptor for dentin matrix protein 1 (DMP1) and is required for DMP1-mediated calcium release; that it is a secreted protein and can bind to type I collagen and DMP1 extracellularly and aid in the nucleation of calcium phosphate. We provide evidence in this study that tyrosine phosphorylation is required for DMP1/GRP-78-mediated calcium release in mesenchymal cells. We further demonstrate that GRP-78 is localized in the nucleus of mesenchymal cells and that the cell surface GRP-78 is not associated with the G-protein Gαq in mesenchymal cells. Results from this study show that during development of mineralized tissues, increased expression of GRP-78 can be observed in condensing cartilage and mesenchymal cells of the alveolar bone, endochondral bone and dental pulp. Additionally, we show that GRP-78 is present in the mineralizing matrices of teeth, bone and in the extracellular matrix of differentiating human marrow stromal cells and dental pulp stem cells. Collectively, our observations provide a new perspective on GRP-78 with respect to mineralized matrix formation.
authors.affiliation: Brodie Tooth Development Genetics and 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.forename: Qi
authors.initials: Q
authors.lastname: Gao
authors.forename: Amsaveni
authors.initials: A
authors.lastname: Ramachandran
authors.forename: Premanand
authors.initials: P
authors.lastname: Sundivakkam
authors.forename: Chinnaswamy
authors.initials: C
authors.lastname: Tiruppathi
authors.forename: Anne
authors.initials: A
authors.lastname: George
mesh_terms: D000818:Animals; D002113:Calcification, Physiologic; D002454:Cell Differentiation; D003782:Dental Pulp / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP; D005109:Extracellular Matrix / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000032:analysis / Q000378:metabolism*; D006801:Humans; D059630:Mesenchymal Stem Cells / Q000378:metabolism*; D051379:Mice; D009928:Organ Specificity; D010766:Phosphorylation
chemical_list: D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins