KCTD1 suppresses canonical Wnt signaling pathway by enhancing Œ≤-catenin degradation
Authors: Zhongheng Liang
Cheng Chen
Xiang Hu
Ke Wei
Yuzhong Xiao
Wenhuan Huang
Xinxin Li
Zhenxing Wan
Shuanglin Xiang
Jian Zhang
Xiaofeng Ding
Fangmei Wang
Journal: PLoS ONE (2014)
Discipline: Multidisciplinary
Keywords: Wnt signaling pathway; Œ≤-catenin; KCTD1; TCF/LEF reporter activity; ubiquitination/degradation
Affiliations: Key Laboratory of Protein Chemistry and Development Biology of State Education Ministry of China, College of Life Science, Hunan Normal University, Changsha, China.

Abstract:  The canonical Wnt signaling pathway controls normal embryonic development, cellular proliferation and growth, and its aberrant activity results in human carcinogenesis. The core component in regulation of this pathway is Œ≤-catenin, but molecular regulation mechanisms of Œ≤-catenin stability are not completely known. Here, our recent studies have shown that KCTD1 strongly inhibits TCF/LEF reporter activity. Moreover, KCTD1 interacted with Œ≤-catenin both in vivo by co-immunoprecipitation as well as in vitro through GST pull-down assays. We further mapped the interaction regions to the 1-9 armadillo repeats of Œ≤-catenin and the BTB domain of KCTD1, especially Position Ala-30 and His-33. Immunofluorescence analysis indicated that KCTD1 promotes the cytoplasmic accumulation of Œ≤-catenin. Furthermore, protein stability assays revealed that KCTD1 enhances the ubiquitination/degradation of Œ≤-catenin in a concentration-dependent manner in HeLa cells. And the degradation of Œ≤-catenin mediated by KCTD1 was alleviated by the proteasome inhibitor, MG132. In addition, KCTD1-mediated Œ≤-catenin degradation was dependent on casein kinase 1 (CK1)- and glycogen synthase kinase-3Œ≤ (GSK-3Œ≤)-mediated phosphorylation and enhanced by the E3 ubiquitin ligase Œ≤-transducin repeat-containing protein (Œ≤-TrCP). Moreover, KCTD1 suppressed the expression of endogenous Wnt downstream genes and transcription factor AP-2Œ±. Finally, we found that Wnt pathway member APC and tumor suppressor p53 influence KCTD1-mediated downregulation of Œ≤-catenin. These results suggest that KCTD1 functions as a novel inhibitor of Wnt signaling pathway. 

Retracted: Yes

PubPeer comments:
 Several concerns about this paper were reported to the journal in October 2015, but nothing has happened so far. * Figure 4C: the righthand side of the blot appears to show many duplications, as marked by me with boxes of the same color. Image made darker to bring out details. * Figure 5B. Unexpected repetitive patterns, marked with dark blue and moss green boxes * Figure 7B and 8C: two lanes in three panels look similar to each other. Might be the same experiment, but panels appear to sometimes be flipped.  , 
 Retraction, 12 May 2022: https: journals.plos.org plosone article?id=10.1371 journal.pone.0268604  Following the publication of this article [1], concerns were raised regarding the results presented in multiple figures. Specifically, * In Fig 4C, there appear to be repetitive elements in the background within and between lanes 5u201310 when color levels are adjusted. * In Fig 5B, there appear to be repetitive elements in the background of lanes 2u20133 when color levels are adjusted. * In Figs 7B and 8C, the following bands appear similar: * u25cb Lanes 1 and 2 of the u03b2-catenin panel in Fig 7B and the u03b2-catenin panel in Fig 8C flipped vertically. * u25cb Lanes 1 and 2 of the KCTD1 panel in Fig 7B and the KCTD1 panel in Fig 8C. * u25cb Lanes 1 and 2 of the u03b2-actin panel in Fig 7B and the u03b2-actin panel in Fig 8C flipped vertically. The corresponding author acknowledged that Figs 4C and 5B contain repetitive elements in the background and stated that the figures were adjusted in error. They provided raw image data underlying Figs 4C and 5B and repeat experiments. The raw data did not resolve the concerns regarding repetitive elements which question the integrity of these data, and the journal does not consider alternative experiment data to be sufficient to address these concerns. The corresponding author stated that the results in lanes 1u20132 of Fig 7B and the results in Fig 8C represent the same experimental conditions. Furthermore, the corresponding author clarified that the u03b2-catenin and u03b2-actin blots in Fig 8C were inadvertently flipped across the horizontal axes during figure preparation. In light of the concerns affecting Figs 4C and 5B that question the integrity of these data, the PLOS ONE Editors retract this article. XL, CC, FW, WH, and XD did not agree with the retraction and stand by the articleu2019s findings. All other authors either did not respond directly or could not be reached. ,