title: The LPV Motif Is Essential for the Efficient Export of Secretory DMP1 From the Endoplasmic Reticulum.
abstract: Dentin matrix protein 1 (DMP1) is found abundantly in the extracellular matrices of bone and dentin. Secretory DMP1 begins with a tripeptide of leucine-proline-valine (LPV) after the endoplasmic reticulum (ER)-entry signal peptide is cleaved. The goal of this study was to determine the role of the LPV motif in the secretion of DMP1. A series of DNA constructs was generated to express various forms of DMP1 with or without the LPV motif. These constructs were transfected into a preosteoblast cell line, the MC3T3-E1 cells, and the subcellular localization and secretion of various forms of DMP1 were examined by immunofluorescent staining and Western-blotting analyses. Immunofluorescent staining showed that the LPV-containing DMP1 variants were primarily localized in the Golgi complex, whereas the LPV-lacking DMP1 variants were found abundantly within the ER. Western-blotting analyses demonstrated that the LPV-containing DMP1 variants were rapidly secreted from the transfected cells, as they did not accumulate within the cells, and the amounts increased in the conditioned media over time. In contrast, the LPV-lacking DMP1 variants were predominantly retained within the cells, and only small amounts were secreted out of the cells over time. These results suggest that the LPV motif is essential for the efficient export of secretory DMP1 from the ER to the Golgi complex.
authors.affiliation: Department of Biomedical Sciences and Center for Craniofacial Research and Diagnosis, Texas A&M University Baylor College of Dentistry, Dallas, Texas.
authors.forename: Tian
authors.initials: T
authors.lastname: Liang
authors.affiliation: Department of Biomedical Sciences and Center for Craniofacial Research and Diagnosis, Texas A&M University Baylor College of Dentistry, Dallas, Texas.
authors.forename: Tian
authors.initials: T
authors.lastname: Meng
authors.affiliation: Department of Biomedical Sciences and Center for Craniofacial Research and Diagnosis, Texas A&M University Baylor College of Dentistry, Dallas, Texas.
authors.forename: Suzhen
authors.initials: S
authors.lastname: Wang
authors.affiliation: Department of Biomedical Sciences and Center for Craniofacial Research and Diagnosis, Texas A&M University Baylor College of Dentistry, Dallas, Texas.
authors.forename: Chunlin
authors.initials: C
authors.lastname: Qin
authors.affiliation: Department of Biomedical Sciences and Center for Craniofacial Research and Diagnosis, Texas A&M University Baylor College of Dentistry, Dallas, Texas.
authors.forename: Yongbo
authors.initials: Y
authors.lastname: Lu
mesh_terms: D016475:3T3 Cells; D020816:Amino Acid Motifs / Q000235:genetics*; D000818:Animals; D003804:Dentin / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism*; D016326:Extracellular Matrix Proteins / Q000235:genetics / Q000378:metabolism*; D006056:Golgi Apparatus / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007930:Leucine / Q000235:genetics; D051379:Mice; D010006:Osteoblasts / Q000378:metabolism; D011392:Proline / Q000235:genetics; D014633:Valine / Q000235:genetics
chemical_list: C513308:Dmp1 protein, mouse; D016326:Extracellular Matrix Proteins; D011392:Proline; D007930:Leucine; D014633:Valine