Identification of the Axin and Frat binding region of glycogen synthase kinase-3.
Glycogen synthase kinase-3 (GSK-3) is a key component of several signaling pathways including those regulated by Wnt and insulin ligands. Specificity in GSK-3 signaling is thought to involve interactions with scaffold proteins that localize GSK-3 regulators and substrates. This report shows that GSK-3 forms a low affinity homodimer that is disrupted by binding to Axin and Frat. Based on the crystal structure of GSK-3, we have used surface-scanning mutagenesis to identify residues that differentially affect GSK-3 interactions. Mutations that disrupt Frat and Axin cluster at the dimer interface explaining their effect on homodimer formation. Loss of the Axin binding site blocks the ability of dominant negative GSK-3 to cause axis duplication in Xenopus embryos. The Axin binding site is conserved within all GSK-3 proteins, and its loss affects both cell motility and gene expression in the nonmetazoan, Dictyostelium. Surprisingly, we find no genetic interaction between a non-Axin-binding GSK-3 mutant and T-cell factor activity, arguing that Axin interactions alone cannot explain the regulation of T-cell factor-mediated gene expression.
Fraser
Elizabeth
E
Cancer Research Campaign Centre for Cell and Molecular Biology and Section of Structural Biology, Institute of Cancer Research, 237 Fulham Rd., London SW3 6JB, United Kingdom.
Young
Neville
N
Dajani
Rana
R
Franca-Koh
Jonathan
J
Ryves
Jonathan
J
Williams
Robin S B
RS
Yeo
Margaret
M
Webster
Marie-Therese
MT
Richardson
Chris
C
Smalley
Matthew J
MJ
Pearl
Laurence H
LH
Harwood
Adrian
A
Dale
Trevor C
TC
D048868:Adaptor Proteins, Signal Transducing; D019943:Amino Acid Substitution; D000818:Animals; D060466:Axin Protein; D001665:Binding Sites; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins; D002460:Cell Line; D018360:Crystallography, X-Ray; D038362:Glycogen Synthase Kinase 3; D038341:Glycogen Synthase Kinases; D006801:Humans; D007150:Immunohistochemistry; D047908:Intracellular Signaling Peptides and Proteins; D008958:Models, Molecular; D016296:Mutagenesis; D009363:Neoplasm Proteins; D011487:Protein Conformation; D011506:Proteins / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D012097:Repressor Proteins; D014981:Xenopus; D029867:Xenopus Proteins
D048868:Adaptor Proteins, Signal Transducing; D060466:Axin Protein; D002352:Carrier Proteins; C491819:FRAT1 protein, human; D047908:Intracellular Signaling Peptides and Proteins; D009363:Neoplasm Proteins; C112892:PIAS1 protein, Xenopus; D011506:Proteins; D011518:Proto-Oncogene Proteins; D012097:Repressor Proteins; D029867:Xenopus Proteins; C555454:axin1 protein, Xenopus; D038341:Glycogen Synthase Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D038362:Glycogen Synthase Kinase 3