title: Analysis of endogenous LRP6 function reveals a novel feedback mechanism by which Wnt negatively regulates its receptor.
abstract: The canonical Wnt pathway plays a crucial role in embryonic development, and its deregulation is involved in human diseases. The LRP6 single-span transmembrane coreceptor is essential for transmission of canonical Wnt signaling. However, due to the lack of immunological reagents, our understanding of LRP6 structure and function has relied on studies involving its overexpression, and regulation of the endogenous receptor by the Wnt ligand has remained unexplored. Using a highly sensitive and specific antibody to LRP6, we demonstrate that the endogenous receptor is modified by N-glycosylation and is phosphorylated in response to Wnt stimulation in a sustained yet ligand-dependent manner. Moreover, following triggering by Wnt, endogenous LRP6 is internalized and recycled back to the cellular membrane within hours of the initial stimulus. Finally, we have identified a novel feedback mechanism by which Wnt, acting through beta-catenin, negatively regulates LRP6 at the mRNA level. Together, these findings contribute significantly to our understanding of LRP6 function and uncover a new level of regulation of Wnt signaling. In light of the direct role that the Wnt pathway plays in human bone diseases and malignancies, our findings may support the development of novel therapeutic approaches that target Wnt signaling through LRP6.
authors: Department of Oncological Sciences, The Mount Sinai School of Medicine, Box 1130, One Gustave L. Levy Place, New York, NY 10029, USA.
authors: Zahid
authors: Z
authors: Khan
authors: Sapna
authors: S
authors: Vijayakumar
authors: Teresa Villanueva
authors: TV
authors: de la Torre
authors: Sabrina
authors: S
authors: Rotolo
authors: Anna
authors: A
authors: Bafico
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D060466:Axin Protein; D002460:Cell Line; D019281:Dimerization; D025461:Feedback, Physiological; D006801:Humans; D008024:Ligands; D060488:Low Density Lipoprotein Receptor-Related Protein-6; D051379:Mice; D011499:Protein Processing, Post-Translational; D011973:Receptors, LDL / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D014158:Transcription, Genetic; D051153:Wnt Proteins / Q000235:genetics / Q000378:metabolism*; D060508:Wnt3 Protein; D051176:beta Catenin / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D060466:Axin Protein; C555475:LRP6 protein, human; D008024:Ligands; D060488:Low Density Lipoprotein Receptor-Related Protein-6; C555476:Lrp6 protein, mouse; D011973:Receptors, LDL; D012097:Repressor Proteins; D051153:Wnt Proteins; D060508:Wnt3 Protein; D051176:beta Catenin
references: Cytokine Growth Factor Rev. 2005 Dec;16(6):637-58
references: 15998596
references: Mol Cell Biol. 2005 May;25(9):3475-82
references: 15831454
references: Nature. 2005 Dec 8;438(7069):873-7
references: 16341017
references: Dev Cell. 2006 Aug;11(2):213-23
references: 16890161
references: J Biol Chem. 2006 Aug 11;281(32):22429-33
references: 16793760
references: BMC Cell Biol. 2006;7:28
references: 16824228
references: Cell. 2006 Nov 3;127(3):469-80
references: 17081971
references: Oncogene. 2006 Dec 4;25(57):7461-8
references: 17143290
references: Cell Signal. 2007 Apr;19(4):659-71
references: 17188462
references: J Biol Chem. 2007 May 25;282(21):15903-11
references: 17400545
references: Genes Dev. 2000 Aug 1;14(15):1837-51
references: 10921899
references: Nature. 2000 Sep 28;407(6803):527-30
references: 11029006
references: Nature. 2000 Sep 28;407(6803):530-5
references: 11029007
references: Nature. 2000 Sep 28;407(6803):535-8
references: 11029008
references: Cell. 2000 Oct 13;103(2):211-25
references: 11057895
references: Mol Cell. 2001 Apr;7(4):801-9
references: 11336703
references: Nature. 2001 May 17;411(6835):321-5
references: 11357136
references: Nat Cell Biol. 2001 Jul;3(7):683-6
references: 11433302
references: Curr Biol. 2001 Jun 26;11(12):951-61
references: 11448771
references: Nat Rev Mol Cell Biol. 2002 Dec;3(12):893-905
references: 12461556
references: Exp Cell Res. 2003 Mar 10;284(1):78-88
references: 12648467
references: Nat Cell Biol. 2003 May;5(5):410-21
references: 12717440
references: J Cell Sci. 2003 Jul 1;116(Pt 13):2627-34
references: 12775774
references: Mol Cell Biol. 2003 Aug;23(16):5825-35
references: 12897152
references: Science. 2003 Sep 5;301(5638):1391-4
references: 12958364
references: Mol Cell. 2004 Jan 16;13(1):149-56
references: 14731402
references: Development. 2004 Apr;131(8):1663-77
references: 15084453
references: Nat Rev Genet. 2004 Sep;5(9):691-701
references: 15372092
references: Development. 2004 Oct;131(20):5103-15
references: 15459103
references: Gene. 2004 Oct 27;341:19-39
references: 15474285
references: FEBS Lett. 2004 Oct 22;576(3):401-7
references: 15498570
references: Proc Natl Acad Sci U S A. 1983 Dec;80(24):7501-5
references: 6143315
references: J Biol Chem. 1988 Feb 25;263(6):2581-4
references: 3343225
references: Mol Endocrinol. 1992 Dec;6(12):2090-102
references: 1491690
references: Nature. 1996 Jul 18;382(6588):225-30
references: 8717036
references: Science. 1997 Mar 21;275(5307):1787-90
references: 9065402
references: Genes Dev. 1997 Dec 15;11(24):3286-305
references: 9407023
references: Oncogene. 1998 May 28;16(21):2819-25
references: 9652750
references: Cancer Cell. 2004 Nov;6(5):497-506
references: 15542433
references: Nat Rev Mol Cell Biol. 2005 Feb;6(2):112-26
references: 15687999
references: Nature. 2005 Dec 8;438(7069):867-72
references: 16341016