Sequence requirement and subtype specificity in the high-affinity interaction between human frizzled and dishevelled proteins.
Members of the Wnt family of lipoglycoproteins initiate signaling by binding to Frizzled (Fz) receptors, and the signal is then relayed by Disheveled (Dvl). The Dvl PDZ domain is known to interact directly with a peptide derived from the KTXXXW motif of Fz7, which is conserved in all known Fz subtypes. We found that an extended region spanning the KTXXXW motif on both its N-terminal and C-terminal sides dramatically influences the affinity of peptides derived from Fz7 for Dvl PDZ. An alanine scanning study identified the specific residues external to the KTXXXW motif that are important for high-affinity binding. In a circular dichroism analysis, mutation of some of these critical residues resulted in peptide conformational changes, suggesting that the secondary structure of the peptides contributes to Fz-Dvl PDZ binding. Of the 10 known Fz subtypes, peptides derived from only Fz1, Fz2, Fz3, Fz4, and Fz7 directly bound to Dvl PDZ domain in our study. Other Fz subtypes, including some known to be involved in Wnt/beta-catenin signaling (Fz5, Fz9), did not bind to Dvl, suggesting that direct interaction with Dvl PDZ does not determine the subtype-specific functionality of Fz. Molecular modeling and circular dichroism studies indicated that the Fz peptides that bind to Dvl PDZ domain form specific conformations that are different from those of nonbinding peptides.
Punchihewa
Chandanamali
C
Department of Chemical Biology and Therapeutics, St. Jude Children's Research Hospital, Memphis, Tennessee 38105-36781, USA.
Ferreira
Antonio M
AM
Cassell
Robert
R
Rodrigues
Patrick
P
Fujii
Naoaki
N
D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D020816:Amino Acid Motifs / Q000235:genetics; D000595:Amino Acid Sequence; D051157:Frizzled Receptors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009010:Monte Carlo Method; D054731:PDZ Domains / Q000235:genetics; D010750:Phosphoproteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D054730:Protein Interaction Domains and Motifs; D013816:Thermodynamics; D051153:Wnt Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D051157:Frizzled Receptors; D010750:Phosphoproteins; D051153:Wnt Proteins