title: Functional analysis of disease-associated polymorphism LRP5.Q89R.
abstract: OBJECTIVE
  The canonical wingless and Int1 (Wnt) signaling pathway plays key roles in multiple biologic events. The pathway co-receptor, low density lipoprotein receptor-related protein 5 (LRP5), is involved in the pathogenesis of retinal diseases and has been implicated in glaucoma. We studied whether a disease-associated polymorphism LRP5.Q89R, which is located in the second blade of the first β-propeller domain, directly alters Wnt signaling activity with cell-based assays.
  
  
  METHODS
  The LRP5.Q89R polymorphism was evaluated by transfection of HEK293T or GTM3 cells with expression vectors. LRP5 expression and interaction with the molecular chaperone mesoderm development (MESD) were determined by western immunoblotting and co-immunoprecipitation analyses. To compare membrane-associated LRP5 proteins, surface proteins were labeled with biotin and pulled down with avidin beads followed by western immunoblotting. TCF-reporter plasmid-based luciferase assays were used to determine whether LRP5.Q89R affects the canonical Wnt signaling, or has altered efficacy to suppression by Dickkopf-1 (DKK-1).
  
  
  RESULTS
  Cell-based assays showed that this polymorphism did not change protein expression, interaction with the molecular chaperone MESD, protein trafficking, Wnt signaling transduction, or its efficacy in DKK1-mediated inhibition.
  
  
  CONCLUSIONS
  Our data suggest that this specific polymorphism does not appear to alter the canonical Wnt signaling pathway. Further studies of LRP5 polymorphisms are needed to elucidate their roles in various associated diseases.
authors.affiliation: Department of Cell Biology & Anatomy, North Texas Eye Research Institute, University of North Texas Health Science Center, Ft. Worth, TX, USA. Weiming.mao@unthsc.edu
authors.forename: Weiming
authors.initials: W
authors.lastname: Mao
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Wordinger
authors.forename: Abbot F
authors.initials: AF
authors.lastname: Clark
mesh_terms: D001120:Arginine / Q000235:genetics / Q000378:metabolism; D015153:Blotting, Western; D002461:Cell Line, Transformed; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D005901:Glaucoma / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology; D005973:Glutamine / Q000235:genetics / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D026502:LDL-Receptor Related Proteins / Q000235:genetics* / Q000378:metabolism*; D060492:Low Density Lipoprotein Receptor-Related Protein-5; D008156:Luciferases / Q000032:analysis; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism; D010957:Plasmids; D011110:Polymorphism, Genetic; D025941:Protein Interaction Mapping; D021381:Protein Transport; D015398:Signal Transduction; D014162:Transfection; D051153:Wnt Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: C501126:DKK1 protein, human; D036341:Intercellular Signaling Peptides and Proteins; D026502:LDL-Receptor Related Proteins; C555482:LRP5 protein, human; D060492:Low Density Lipoprotein Receptor-Related Protein-5; C506348:MESD protein, human; D018832:Molecular Chaperones; D051153:Wnt Proteins; D005973:Glutamine; D001120:Arginine; D008156:Luciferases