Characterization of the Kremen-binding site on Dkk1 and elucidation of the role of Kremen in Dkk-mediated Wnt antagonism.
Wnt signaling is involved in a wide range of developmental, physiological, and pathophysiological processes and is negatively regulated by Dickkopf1 (Dkk1). Dkk1 has been shown to bind to two transmembrane proteins, the low density lipoprotein receptor-related proteins (LRP) 5/6 and Kremen. Here, we show that Dkk1 residues Arg(197), Ser(198), and Lys(232) are specifically involved in its binding to Kremen rather than to LRP6. These residues are localized at a surface that is at the opposite side of the LRP6-binding surface based on a three-dimensional structure of Dkk1 deduced from that of Dkk2. We were surprised to find that the Dkk1 mutants carrying a mutation at Arg(197), Ser(198), or Lys(232), the key Kremen-binding residues, could antagonize Wnt signaling as well as the wild-type Dkk1. These mutations only affected their ability to antagonize Wnt signaling when both LRP6 and Kremen were coexpressed. These results suggest that Kremen may not be essential for Dkk1-mediated Wnt antagonism and that Kremen may only play a role when cells express a high level of LRP5/6.
Wang
Ke
K
State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China.
Zhang
Yazhou
Y
Li
Xiaofeng
X
Chen
Lijun
L
Wang
He
H
Wu
Jianguo
J
Zheng
Jie
J
Wu
Dianqing
D
D000818:Animals; D001665:Binding Sites; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000737:chemistry* / Q000378:metabolism; D026502:LDL-Receptor Related Proteins / Q000737:chemistry; D060492:Low Density Lipoprotein Receptor-Related Protein-5; D060488:Low Density Lipoprotein Receptor-Related Protein-6; D008565:Membrane Proteins / Q000737:chemistry*; D051379:Mice; D008968:Molecular Conformation; D017434:Protein Structure, Tertiary; D051153:Wnt Proteins / Q000378:metabolism*
D036341:Intercellular Signaling Peptides and Proteins; D026502:LDL-Receptor Related Proteins; D060492:Low Density Lipoprotein Receptor-Related Protein-5; D060488:Low Density Lipoprotein Receptor-Related Protein-6; D008565:Membrane Proteins; D051153:Wnt Proteins; C501126:DKK1 protein, human; C501127:Dkk1 protein, mouse; C486075:KREMEN1 protein, human; C486077:Kremen1 protein, mouse; C555482:LRP5 protein, human; C555475:LRP6 protein, human; C555483:Lrp5 protein, mouse; C555476:Lrp6 protein, mouse