LRP6

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Identifiers
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External IDsGeneCards: [1]
Orthologs
SpeciesHumanMouse
Entrez
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RefSeq (mRNA)

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RefSeq (protein)

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Low-density lipoprotein receptor-related protein 6 is a protein that in humans is encoded by the LRP6 gene.[1][2] LRP6 is a key component of the LRP5/LRP6/Frizzled co-receptor group that is involved in canonical Wnt pathway.

Structure

LRP6 is a transmembrane low-density lipoprotein receptor that shares a similar structure with LRP5. In each protein, about 85% of its 1600-amino-acid length is extracellular. Each has four β-propeller motifs at the amino terminal end that alternate with four epidermal growth factor (EGF)-like repeats. Most extracellular ligands bind to LRP5 and LRP6 at the β-propellers. Each protein has a single-pass, 22-amino-acid segment that crosses the cell membrane and a 207-amino-acid segment that is internal to the cell.[3]

Function

LRP6 acts as a co-receptor with LRP5 and the Frizzled protein family members for transducing signals by Wnt proteins through the canonical Wnt pathway.[3]

Interactions

Canonical WNT signals are transduced through Frizzled receptor and LRP5/LRP6 coreceptor to downregulate GSK3beta (GSK3B) activity not depending on Ser-9 phosphorylation.[4] Reduction of canonical Wnt signals upon depletion of LRP5 and LRP6 results in p120-catenin degradation.[5]

LRP6 is regulated by extracellular proteins in the Dickkopf (Dkk) family (like DKK1[6]), sclerostin, R-spondins and members of the cysteine-knot-type protein family.[3]

Clinical significance

Loss-of-function mutations or LRP6 in humans lead to increased plasma LDL and triglycerides, hypertension, diabetes and osteoporosis.[3] Similarly, mice with a loss-of-function Lrp6 mutation have low bone mass.[7] LRP6 is critical in bone's anabolic response to parathyroid hormone (PTH) treatment, whereas LRP5 is not involved.[7] On the other hand, LRP6 does not appear active in mechanotransduction (bone's response to forces), while LRP5 is critical in that role.[7] Sclerostin, one of the inhibitors of LRP6, is a promising osteocyte-specific Wnt antagonist in osteoporosis clinical trials.[8][9]

References

  1. Brown SD, Twells RC, Hey PJ, Cox RD, Levy ER, Soderman AR, Metzker ML, Caskey CT, Todd JA, Hess JF (1998). "Isolation and characterization of LRP6, a novel member of the low density lipoprotein receptor gene family". Biochem. Biophys. Res. Commun. 248 (3): 879–88. doi:10.1006/bbrc.1998.9061. PMID 9704021.
  2. "Entrez Gene: LRP6 low density lipoprotein receptor-related protein 6".
  3. 3.0 3.1 3.2 3.3 Williams BO, Insogna KL (2009). "Where Wnts went: the exploding field of Lrp5 and Lrp6 signaling in bone". J. Bone Miner. Res. 24 (2): 171–8. doi:10.1359/jbmr.081235. PMC 3276354. PMID 19072724.
  4. Katoh M, Katoh M (2006). "Cross-talk of WNT and FGF signaling pathways at GSK3beta to regulate beta-catenin and SNAIL signaling cascades". Cancer Biol. Ther. 5 (9): 1059–64. doi:10.4161/cbt.5.9.3151. PMID 16940750.
  5. Hong JY, Park JI, Cho K, Gu D, Ji H, Artandi SE, McCrea PD (2010). "Shared molecular mechanisms regulate multiple catenin proteins: canonical Wnt signals and components modulate p120-catenin isoform-1 and additional p120 subfamily members". J. Cell Sci. 123 (Pt 24): 4351–65. doi:10.1242/jcs.067199. PMC 2995616. PMID 21098636.
  6. Semënov MV, Tamai K, Brott BK, Kühl M, Sokol S, He X (2001). "Head inducer Dickkopf-1 is a ligand for Wnt coreceptor LRP6". Curr. Biol. 11 (12): 951–61. doi:10.1016/s0960-9822(01)00290-1. PMID 11448771.
  7. 7.0 7.1 7.2 Kang KS, Robling AG (2014). "New Insights into Wnt-Lrp5/6-β-Catenin Signaling in Mechanotransduction". Front Endocrinol (Lausanne). 5: 246. doi:10.3389/fendo.2014.00246. PMC 4299511. PMID 25653639.
  8. Baron R, Kneissel M (February 2013). "WNT signaling in bone homeostasis and disease: from human mutations to treatments". Nature Medicine. 19 (2): 179–192. doi:10.1038/nm.3074. PMID 23389618.
  9. Burgers TA, Williams BO (June 2013). "Regulation of Wnt/beta-catenin signaling within and from osteocytes". Bone. 54 (2): 244–249. doi:10.1016/j.bone.2013.02.022. PMC 3652284. PMID 23470835.

Further reading



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