title: Casein kinase I and casein kinase II differentially regulate axin function in Wnt and JNK pathways.
abstract: Axin uses different combinations of functional domains in down-regulation of the Wnt pathway and activation of the MEKK1/JNK pathway. We are interested in the elucidation of the functional switch of Axin. In the present study, we show that the Wnt activator CKIepsilon, but not CKIIalpha, Frat1, LRP5, or LRP6, inhibited Axin-mediated JNK activation. We also found that both CKIalpha and CKIepsilon interacted with Axin, whereas CKIIalpha did not bind to Axin and had no effect on Axin-mediated JNK activity even though CKIIalpha has also been suggested to be an activator for the Wnt pathway. The COOH-terminal region and the MEKK1-interacting domain of Axin are important for CKIalpha-Axin and CKIepsilon-Axin interaction. We further demonstrated that CKIepsilon and CKIalpha binding to Axin excluded MEKK1 binding, indicating that a competitive physical occupancy may underlie the inhibitory effect. Moreover, our data indicated that CKIepsilon kinase activity plays an additive role in this effect. Taken together, we have demonstrated that CKI and CKII exhibit differential effects on Axin-MEKK1 interaction and Axin-mediated JNK activation. Furthermore, our data suggest that CKI may provide a possible switch mechanism for Axin function in the regulation of Wnt and JNK pathways.
authors.affiliation: Department of Biochemistry, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
authors.forename: Wen-Jie
authors.initials: WJ
authors.lastname: Qiu
authors.forename: Siu Chiu
authors.initials: SC
authors.lastname: Chan
authors.forename: Jiahuai
authors.initials: J
authors.lastname: Han
authors.forename: Xi
authors.initials: X
authors.lastname: He
authors.forename: Sheng-Cai
authors.initials: SC
authors.lastname: Lin
mesh_terms: D000818:Animals; D060466:Axin Protein; D047390:Casein Kinase II; D047388:Casein Kinases; D002478:Cells, Cultured; D004789:Enzyme Activation; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases; D048728:MAP Kinase Kinase Kinase 1; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology*; D010449:Peptide Mapping; D011485:Protein Binding; D011494:Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism* / Q000502:physiology; D011506:Proteins / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D012097:Repressor Proteins; D051153:Wnt Proteins; D029961:Zebrafish Proteins
chemical_list: D060466:Axin Protein; D007527:Isoenzymes; D011506:Proteins; D011518:Proto-Oncogene Proteins; D012097:Repressor Proteins; D051153:Wnt Proteins; D029961:Zebrafish Proteins; D011494:Protein Kinases; D047390:Casein Kinase II; D047388:Casein 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