title: Secreted Frizzled-related protein-2 (sFRP2) augments canonical Wnt3a-induced signaling.
abstract: Secreted Frizzled-related proteins (sFRP) are involved in embryonic development as well as pathological conditions including bone and myocardial disorders and cancer. Because of their sequence homology with the Wnt-binding domain of Frizzled, they have generally been considered antagonists of canonical Wnt signaling. However, additional activities of various sFRPs including both synergism and mimicry of Wnt signaling as well as functions other than modulation of Wnt signaling have been reported. Using human embryonic kidney cells (HEK293A), we found that sFRP2 enhanced Wnt3a-dependent phosphorylation of LRP6 as well as both cytosolic β-catenin levels and its nuclear translocation. While addition of recombinant sFRP2 had no activity by itself, Top/Fop luciferase reporter assays showed a dose-dependent increase of Wnt3a-mediated transcriptional activity. sFRP2 enhancement of Wnt3a signaling was abolished by treatment with the Wnt antagonist, Dickkopf-1 (DKK1). Wnt-signaling pathway qPCR arrays showed that sFRP2 enhanced the Wnt3a-mediated transcriptional up-regulation of several genes regulated by Wnt3a including its antagonists, DKK1, and Naked cuticle-1 homolog (NKD1). These results support sFRP2's role as an enhancer of Wnt/β-catenin signaling, a result with biological impact for both normal development and diverse pathologies such as tumorigenesis.
authors: Craniofacial and Skeletal Diseases Branch, NIDCR, NIH, DHHS, Bethesda, MD, USA.
authors: Zofia
authors: Z
authors: von Marschall
authors: Larry W
authors: LW
authors: Fisher
mesh_terms: D021581:Active Transport, Cell Nucleus; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D026502:LDL-Receptor Related Proteins / Q000378:metabolism; D060488:Low Density Lipoprotein Receptor-Related Protein-6; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D010766:Phosphorylation; D055550:Protein Stability; D015398:Signal Transduction; D014158:Transcription, Genetic; D051153:Wnt Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D060508:Wnt3 Protein; D060509:Wnt3A Protein; D051176:beta Catenin / Q000378:metabolism; D000094742:Secreted Frizzled-Related Proteins
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; D036341:Intercellular Signaling Peptides and Proteins; D026502:LDL-Receptor Related Proteins; D060488:Low Density Lipoprotein Receptor-Related Protein-6; D008565:Membrane Proteins; D051153:Wnt Proteins; D060508:Wnt3 Protein; D060509:Wnt3A Protein; D051176:beta Catenin; C501126:DKK1 protein, human; C555475:LRP6 protein, human; C555476:Lrp6 protein, mouse; C449091:NKD1 protein, human; C109618:SFRP2 protein, human; D000094742:Secreted Frizzled-Related Proteins; C555510:WNT3A protein, human; C555511:Wnt3a protein, mouse