title: The first propeller domain of LRP6 regulates sensitivity to DKK1.
abstract: The Wnt coreceptor LRP6 is required for canonical Wnt signaling. To understand the molecular regulation of LRP6 function, we generated a series of monoclonal antibodies against the extra cellular domain (ECD) of LRP6 and selected a high-affinity mAb (mAb135) that recognizes cell surface expression of endogenous LRP6. mAb135 enhanced Wnt dependent TCF reporter activation and antagonized DKK1 dependent inhibition of Wnt3A signaling, suggesting a role in modulation of LRP6 function. Detailed analysis of LRP6 domain mutants identified Ser 243 in the first propeller domain of LRP6 as a critical residue for mAb135 binding, implicating this domain in regulating the sensitivity of LRP6 to DKK1. In agreement with this notion, mAb135 directly disrupted the interaction of DKK1 with recombinant ECD LRP6 and a truncated form of the LRP6 ECD containing only repeats 1 and 2. Finally, we found that mAb135 completely protected LRP6 from DKK1 dependent internalization. Together, these results identify the first propeller domain as a novel regulatory domain for DKK1 binding to LRP6 and show that mAb against the first propeller domain of LRP6 can be used to modulate this interaction.
authors.affiliation: Arca Biopharma, San Carlos, CA 94070-6211, USA. minkebinnerts@mindspring.com
authors.forename: Minke E
authors.initials: ME
authors.lastname: Binnerts
authors.forename: Nenad
authors.initials: N
authors.lastname: Tomasevic
authors.forename: Jessica M
authors.initials: JM
authors.lastname: Bright
authors.forename: John
authors.initials: J
authors.lastname: Leung
authors.forename: Victoria E
authors.initials: VE
authors.lastname: Ahn
authors.forename: Kyung-Ah
authors.initials: KA
authors.lastname: Kim
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Zhan
authors.forename: Shouchun
authors.initials: S
authors.lastname: Liu
authors.forename: Shirlee
authors.initials: S
authors.lastname: Yonkovich
authors.forename: Jason
authors.initials: J
authors.lastname: Williams
authors.forename: Mei
authors.initials: M
authors.lastname: Zhou
authors.forename: Delphine
authors.initials: D
authors.lastname: Gros
authors.forename: Melissa
authors.initials: M
authors.lastname: Dixon
authors.forename: Wouter
authors.initials: W
authors.lastname: Korver
authors.forename: William I
authors.initials: WI
authors.lastname: Weis
authors.forename: Arie
authors.initials: A
authors.lastname: Abo
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology / Q000494:pharmacology; D001665:Binding Sites / Q000235:genetics / Q000276:immunology; D015153:Blotting, Western; D002460:Cell Line; D004705:Endocytosis / Q000187:drug effects; D005434:Flow Cytometry; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D026502:LDL-Receptor Related Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D060488:Low Density Lipoprotein Receptor-Related Protein-6; D009154:Mutation; D011485:Protein Binding / Q000187:drug effects; D034622:RNA Interference; D015398:Signal Transduction / Q000187:drug effects; D051153:Wnt Proteins / Q000235:genetics / Q000378:metabolism; D060508:Wnt3 Protein; D060509:Wnt3A Protein
chemical_list: D000911:Antibodies, Monoclonal; C501126:DKK1 protein, human; D036341:Intercellular Signaling Peptides and Proteins; D026502:LDL-Receptor Related Proteins; C555475:LRP6 protein, human; D060488:Low Density Lipoprotein Receptor-Related Protein-6; C555510:WNT3A protein, human; D051153:Wnt Proteins; D060508:Wnt3 Protein; D060509:Wnt3A Protein