title: SUMO-1 modification of the C-terminal KVEKVD of Axin is required for JNK activation but has no effect on Wnt signaling.
abstract: Axin is a multifunctional protein, regulating Wnt signaling and the c-Jun N-terminal/stress-activated protein kinase (JNK/SAPK) pathway as well as tumorigenesis. In the present study, we found that Axin interacts with three SUMO-1 (small ubiquitin-related modifier) conjugating enzymes 3 (E3), PIAS1, PIASxbeta, and PIASy. The extreme C-terminal six amino acid residues of Axin are critical for the Axin/E3 interaction as deletion of the six residues (AxinDeltaC6) completely abolished the ability of Axin to interact with E3 enzymes. AxinDeltaC6 also failed to activate JNK, although it was intact in both its interaction with MEKK1 and homodimerization. Consistent with the presence of a doublet of the KV(E/D) sumoylation consensus motif at the C-terminal end (KVEKVD), we found that Axin is heavily sumoylated. Deletion of the C-terminal six amino acids drastically reduced sumoylation, indicating that the C-terminal six amino acids stretch is the main sumoylation site for Axin. Sumoylation-defective mutants failed to activate JNK but effectively destabilized beta-catenin and attenuated LEF1 transcriptional activity. In addition, we show that dominant negative Axin mutants blocked PIAS-mediated JNK activation, in accordance with the requirement of sumoylation for Axin-mediated JNK activation. Taken together, we demonstrate that sumoylation plays a role for Axin to function in the JNK pathway.
authors.affiliation: Department of Biochemistry, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
authors.forename: Hong-Liang
authors.initials: HL
authors.lastname: Rui
authors.forename: Ernest
authors.initials: E
authors.lastname: Fan
authors.forename: Hai-Meng
authors.initials: HM
authors.lastname: Zhou
authors.forename: Zhen
authors.initials: Z
authors.lastname: Xu
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
authors.forename: Sheng-Cai
authors.initials: SC
authors.lastname: Lin
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D060466:Axin Protein; D001665:Binding Sites; D002460:Cell Line; D003001:Cloning, Molecular; D016384:Consensus Sequence; D004268:DNA-Binding Proteins / Q000378:metabolism; D019281:Dimerization; D004789:Enzyme Activation; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D007668:Kidney; D051821:Lymphoid Enhancer-Binding Factor 1; D048728:MAP Kinase Kinase Kinase 1; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry; D011499:Protein Processing, Post-Translational; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000502:physiology; D011506:Proteins / Q000737:chemistry* / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D012097:Repressor Proteins; D025842:SUMO-1 Protein / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics; D017384:Sequence Deletion; D015398:Signal Transduction / Q000502:physiology*; D014157:Transcription Factors / Q000378:metabolism; D051153:Wnt Proteins; D029961:Zebrafish Proteins
chemical_list: D060466:Axin Protein; D004268:DNA-Binding Proteins; C497573:LEF1 protein, human; C497574:Lef1 protein, mouse; D051821:Lymphoid Enhancer-Binding Factor 1; D010446:Peptide Fragments; D011506:Proteins; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D012097:Repressor Proteins; D025842:SUMO-1 Protein; D014157:Transcription Factors; D051153:Wnt Proteins; D029961:Zebrafish Proteins; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048728:MAP Kinase Kinase Kinase 1; C482576:MAP3K1 protein, human; C482578:Map3k1 protein, mouse