title: The low density lipoprotein receptor-1, LRP1, interacts with the human frizzled-1 (HFz1) and down-regulates the canonical Wnt signaling pathway.
abstract: Members of the low density lipoprotein receptor family (LDLR), LRP5/6, were shown to interact with the Frizzled (Fz) receptors and to function as Wnt coreceptors. Here we show that mLRP4T100, a minireceptor of LRP1, another member of the LDLR family, interacts with the human Fz-1 (HFz1), previously shown to serve as a receptor transmitting the canonical Wnt-3a-induced signaling cascade. However, in contrast to LRP5/6, mLRP4T100, as well as the full-length LRP1, did not cooperate with HFz1 in transmitting the Wnt-3a signaling but rather repressed it. mLRP4T100 inhibitory effect was displayed also by endocytosis-defective mLRP4T100 mutants, suggesting that LRP1 repressive effect is not attributable to LRP1-mediated enhanced HFz1 internalization and subsequent degradation. Enforced expression of mLRP4T100 decreased the capacity of HFz1 cysteine-rich domain (CRD) to interact with LRP6, in contrast to HFz1-CRD/Wnt-3a interaction that was not disrupted by overexpressing mLRP4T100. These data suggest that LRP1, by sequestering HFz1, disrupts the receptor/coreceptor complex formation, leading to the repression of the canonical Wnt signaling. Thus, this study implies that the ability to interact with Fz receptors is shared by several members of the LDLR family. However, whereas some members of the LDLR family, such as LRP5/6, interact with Fz and serve as Wnt coreceptors, others negatively regulate Wnt signaling, presumably by sequestering Fz.
authors.affiliation: Department of Human Microbiology, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel.
authors.forename: Alona
authors.initials: A
authors.lastname: Zilberberg
authors.forename: Abraham
authors.initials: A
authors.lastname: Yaniv
authors.forename: Arnona
authors.initials: A
authors.lastname: Gazit
mesh_terms: D015153:Blotting, Western; D002460:Cell Line; D003001:Cloning, Molecular; D003545:Cysteine / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D051157:Frizzled Receptors; D017930:Genes, Reporter; D005822:Genetic Vectors; D006801:Humans; D008024:Ligands; D026503:Low Density Lipoprotein Receptor-Related Protein-1 / Q000378:metabolism / Q000502:physiology*; D008156:Luciferases / Q000378:metabolism; D008856:Microscopy, Fluorescence; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D017981:Receptors, Neurotransmitter / Q000378:metabolism*; D015398:Signal Transduction; D013997:Time Factors; D014162:Transfection; D051153:Wnt Proteins; D060508:Wnt3 Protein; D060509:Wnt3A Protein; D029961:Zebrafish Proteins; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: C489740:FZD1 protein, human; D051157:Frizzled Receptors; D008024:Ligands; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D011506:Proteins; D011518:Proto-Oncogene Proteins; D017981:Receptors, Neurotransmitter; C555510:WNT3A protein, human; D051153:Wnt Proteins; D060508:Wnt3 Protein; D060509:Wnt3A Protein; D029961:Zebrafish Proteins; D008156:Luciferases; D001616:beta-Galactosidase; D003545:Cysteine