title: Influence of an LRP5 cytoplasmic SNP on Wnt signaling and osteoblastic differentiation.
abstract: The low density lipoprotein receptor-related protein 5 (LRP5) is a key determinant of bone mass, via the Wnt signaling pathway control of osteoblast function. This study examined human LRP5 signaling and the effects of an intracellular domain single nucleotide polymorphism (SNP: p.V1525A) on osteoblast differentiation and mineralization. Constitutively active LRP5 was constructed by deletion of the extracellular domain of LRP5 (LRP5DeltaN). Expression of LRP5DeltaN-V, which carries the allele p.1525V, induced higher beta-catenin/TCF-LEF activity compared to LRP5DeltaN-A, which carries the allele p.1525A. In a yeast two-hybrid assay, LRP5DeltaN-V also demonstrated a stronger interaction with AXIN than LRP5DeltaN-A. Expression of either of the alleles did not change cell proliferation. However, cells expressing LRP5DeltaN-V showed increased alkaline phosphatase activity and bone nodule formation compared to cells transfected with empty vector or LRP5DeltaN-A after osteogenic supplement (OS: beta-glycerophosphate and l-ascorbic acid) treatment. Cells expressing LRP5DeltaN-V revealed significantly increased bone sialoprotein (BSP) expression after 7 days of OS treatment and maintained elevated expression until day 21. Osteocalcin (OCN) mRNA levels were increased after 14-21 days of OS treatment in LRP5DeltaN-V expressing cells. LRP5DeltaN-V expressing cells demonstrated positive interaction with BMP-2 signaling of transcription at the SBE-luc promoter. LRP5 signaling is affected by the cytoplasmic SNP, p.V1525A. mRNA levels of Runx2 and Osterix were not affected by this SNP.
authors.affiliation: Curriculum in Oral Biology, Bone Biology and Implant Therapy Laboratory, 404 Brauer Hall, CB# 7450 School of Dentistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7455, USA.
authors.forename: J
authors.initials: J
authors.lastname: Guo
authors.forename: L F
authors.initials: LF
authors.lastname: Cooper
mesh_terms: D000469:Alkaline Phosphatase / Q000032:analysis / Q000378:metabolism; D000483:Alleles; D060466:Axin Protein; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000378:metabolism; D002454:Cell Differentiation / Q000235:genetics*; D002478:Cells, Cultured; D050659:Core Binding Factor Alpha 1 Subunit / Q000235:genetics / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D006801:Humans; D026502:LDL-Receptor Related Proteins / Q000235:genetics* / Q000378:metabolism; D060492:Low Density Lipoprotein Receptor-Related Protein-5; D010006:Osteoblasts / Q000166:cytology* / Q000378:metabolism; D015675:Osteocalcin / Q000235:genetics / Q000378:metabolism; D020641:Polymorphism, Single Nucleotide; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism; D017384:Sequence Deletion; D015398:Signal Transduction; D000076182:Sp7 Transcription Factor; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000378:metabolism; D020798:Two-Hybrid System Techniques; D051153:Wnt Proteins / Q000378:metabolism*; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism
chemical_list: D060466:Axin Protein; C525718:BMP2 protein, human; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D050659:Core Binding Factor Alpha 1 Subunit; D026502:LDL-Receptor Related Proteins; C555482:LRP5 protein, human; D060492:Low Density Lipoprotein Receptor-Related Protein-5; D012333:RNA, Messenger; D012097:Repressor Proteins; D000076182:Sp7 Transcription Factor; C478163:SP7 protein, human; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D051153:Wnt Proteins; D051176:beta Catenin; D015675:Osteocalcin; D000469:Alkaline Phosphatase