I-mfa domain proteins interact with Axin and affect its regulation of the Wnt and c-Jun N-terminal kinase signaling pathways.
I-mfa has been identified as an inhibitor of myogenic basic helix-loop-helix transcription factors, and a related human I-mfa domain-containing protein (HIC) also has been identified as a protein that regulates Tat- and Tax-mediated expression of viral promoters. HIC and I-mfa represent a family of proteins that share a highly conserved cysteine-rich domain, termed the I-mfa domain. We show here that both I-mfa domain proteins, HIC and I-mfa, interacted in vivo with the Axin complex through their C-terminal I-mfa domains. This interaction inhibited Axin-mediated downregulation of free levels of cytosolic beta-catenin. I-mfa and HIC also both directly interacted with lymphocyte enhancer factor (LEF); however, I-mfa but not HIC significantly inhibited reporter constructs regulated by beta-catenin. The overexpression of HIC but not I-mfa decreased the inhibitory effects of Axin on beta-catenin-regulated reporter constructs, while both HIC and I-mfa decreased Axin-mediated c-Jun N-terminal kinase (JNK) activation. These data reveal for the first time that I-mfa domain proteins interact with the Axin complex and affect Axin regulation of both the Wnt and the JNK activation pathways. Interestingly, HIC differs from I-mfa in that I-mfa affects both Axin function and T-cell factor- or LEF-regulated transcription in the Wnt signaling pathway while HIC affects primarily Axin function.
Kusano
Shuichi
S
Lineberger Comprehensive Cancer Center, School of Medicine, University of North Carolina, Chapel Hill, 27599-7295, USA.
Raab-Traub
Nancy
N
D020816:Amino Acid Motifs; D000818:Animals; D060466:Axin Protein; D015153:Blotting, Western; D019556:COS Cells; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002460:Cell Line; D003545:Cysteine / Q000737:chemistry; D003598:Cytoskeletal Proteins / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D015536:Down-Regulation; D004591:Electrophoresis, Polyacrylamide Gel; D015723:Gene Library; D005982:Glutathione Transferase / Q000378:metabolism; D038362:Glycogen Synthase Kinase 3; D006801:Humans; D015151:Immunoblotting; D048031:JNK Mitogen-Activated Protein Kinases; D008156:Luciferases / Q000378:metabolism; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008957:Models, Genetic; D018006:Myogenic Regulatory Factors / Q000737:chemistry / Q000378:metabolism*; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000378:metabolism*; D012097:Repressor Proteins; D015398:Signal Transduction; D015534:Trans-Activators / Q000378:metabolism; D051153:Wnt Proteins; D014981:Xenopus; D029867:Xenopus Proteins; D029961:Zebrafish Proteins; D051176:beta Catenin
D060466:Axin Protein; C495266:CTNNB1 protein, Xenopus; C495270:CTNNB1 protein, human; D003598:Cytoskeletal Proteins; D018006:Myogenic Regulatory Factors; D011506:Proteins; D011518:Proto-Oncogene Proteins; D012097:Repressor Proteins; D015534:Trans-Activators; D051153:Wnt Proteins; D029867:Xenopus Proteins; D029961:Zebrafish Proteins; C555454:axin1 protein, Xenopus; D051176:beta Catenin; C101295:MDFI protein, human; D008156:Luciferases; D005982:Glutathione Transferase; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D038362:Glycogen Synthase Kinase 3; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases; D003545:Cysteine