Increasing evidence shows that there is an interaction between mitogen-activated protein kinase (MAPK) and Wnt signaling and that their interaction plays important roles in a variety of cellular processes.However, how the two signaling interacts is not clear.Previous studies suggest distinct functions of JNK1 and JNK2, both are MAPK members.Therefore, we investigated their interaction and regulation of Wnt/β-catenin respectively.First, we found that β-catenin expression was strikingly increased in the intestinal normal mucosa and tumors of JNKl-deficient mice by immunohistochemical staining, and that both β-catenin expression and transcriptional activity were significantly upregulated in JNKl-deficent mouse embryonic fibrobtasts (MEFs).However, active JNK1 significantly inhibited β-catenin expression and suppressed β-catenin-mediated transcription activity by enhancing glycogen synthase kinase 3β (GSK3β) activity.But β-catenin inhibition was reduced by GSK3 β inhibitor lithium chloride and proteasome inhibitor MG132.Further, mutant β-catenin at the phosphorylation sites of Ser33 and Ser37 by GSK3β was resistant to activated JNK1-induced β-catenin degradation.Moreover, the physical interaction between JNK1 and β-catenin was detected by immunoprecipitation, and their co-localization was seen in cellular nuclei and cytoplasm assayed by confocal microscopy.Second, similar approaches were utilized to investigate the crosstalk between JNK2 and Wnt-β-catenin in vitro.We found that like JNK1, JNK2 physically interacted with and negatively regulated β-catenin, in which GSK3β and proteasome pathway were also involved.In conclusion, our data provides direct evidence that both JNK1 and JNK2 interact with and negatively regulate Wnt/β-catenin signaling through increasing GSK3β activity.The interaction between JNK1/2 and β-catenin might play an important role in the maintenance of intestinal homeostasis and in the modulation of intestinal tumorigenesis.