Chun-Hui Lan1, Dongfeng Chen2, Bin Wang3,4, Liang Zhang5, Qin Liu5, Ke-Wei Liu5, Zhong-Yi Qin5, Guang-Xi Zhu5, Li-Ting Shen5, Ni Zhang5, Bi-Ying Liu5, Lin-Rong Che5, Jin-Yang Li5, Tao Wang5, Liang-Zhi Wen5, Kai-Jun Liu5, Yan Guo5, Xin-Ru Yin5, Xing-Wei Wang5, Zhi-Hua Zhou6, Hua-Liang Xiao7, You-Hong Cui8, Xiu-Wu Bian8. 1. Department of Gastroenterology, Daping Hospital, Army Medical University (Third Military Medical University), Chongqing, 400042, People's Republic of China. lanchunhui@tmmu.edu.cn. 2. Department of Gastroenterology, Daping Hospital, Army Medical University (Third Military Medical University), Chongqing, 400042, People's Republic of China. chendf1981@126.com. 3. Department of Gastroenterology, Daping Hospital, Army Medical University (Third Military Medical University), Chongqing, 400042, People's Republic of China. wb_tmmu@126.com. 4. Institute of Pathology and Southwest Cancer Center, Key Laboratory of Tumor Immunopathology of Ministry of Education of China, Southwest Hospital, Army Medical University (Third Military Medical University), Chongqing, 400038, People's Republic of China. wb_tmmu@126.com. 5. Department of Gastroenterology, Daping Hospital, Army Medical University (Third Military Medical University), Chongqing, 400042, People's Republic of China. 6. Department of Pathology, The 904 Hospital of People Liberation Army, Wuxi, People's Republic of China. 7. Department of Pathology, Daping Hospital, Army Medical University (Third Military Medical University), Chongqing, 400042, People's Republic of China. 8. Institute of Pathology and Southwest Cancer Center, Key Laboratory of Tumor Immunopathology of Ministry of Education of China, Southwest Hospital, Army Medical University (Third Military Medical University), Chongqing, 400038, People's Republic of China.
Abstract
BACKGROUND: Aberrant activation of Wnt/β-catenin signaling by dysregulated post-translational protein modifications, especially ubiquitination is causally linked to cancer development and progression. Although Lys48-linked ubiquitination is known to regulate Wnt/β-catenin signaling, it remains largely obscure how other types of ubiquitination, such as linear ubiquitination governs its signaling activity. METHODS: The expression and regulatory mechanism of linear ubiquitin chain assembly complex (LUBAC) on Wnt/β-catenin signaling was examined by immunoprecipitation, western blot and immunohistochemical staining. The ubiquitination status of β-catenin was detected by ubiquitination assay. The impacts of SHARPIN, a core component of LUBAC on malignant behaviors of gastric cancer cells were determined by various functional assays in vitro and in vivo. RESULTS: Unlike a canonical role in promoting linear ubiquitination, SHARPIN specifically interacts with β-catenin to maintain its protein stability. Mechanistically, SHARPIN competes with the E3 ubiquitin ligase β-Trcp1 for β-catenin binding, thereby decreasing β-catenin ubiquitination levels to abolish its proteasomal degradation. Importantly, SHARPIN is required for invasiveness and malignant growth of gastric cancer cells in vitro and in vivo, a function that is largely dependent on its binding partner β-catenin. In line with these findings, elevated expression of SHARPIN in gastric cancer tissues is associated with disease malignancy and correlates with β-catenin expression levels. CONCLUSIONS: Our findings reveal a novel molecular link connecting linear ubiquitination machinery and Wnt/β-catenin signaling via SHARPIN-mediated stabilization of β-catenin. Targeting the linear ubiquitination-independent function of SHARPIN could be exploited to inhibit the hyperactive β-catenin signaling in a subset of human gastric cancers.
BACKGROUND: Aberrant activation of Wnt/β-catenin signaling by dysregulated post-translational protein modifications, especially ubiquitination is causally linked to cancer development and progression. Although Lys48-linked ubiquitination is known to regulate Wnt/β-catenin signaling, it remains largely obscure how other types of ubiquitination, such as linear ubiquitination governs its signaling activity. METHODS: The expression and regulatory mechanism of linear ubiquitin chain assembly complex (LUBAC) on Wnt/β-catenin signaling was examined by immunoprecipitation, western blot and immunohistochemical staining. The ubiquitination status of β-catenin was detected by ubiquitination assay. The impacts of SHARPIN, a core component of LUBAC on malignant behaviors of gastric cancer cells were determined by various functional assays in vitro and in vivo. RESULTS: Unlike a canonical role in promoting linear ubiquitination, SHARPIN specifically interacts with β-catenin to maintain its protein stability. Mechanistically, SHARPIN competes with the E3 ubiquitin ligase β-Trcp1 for β-catenin binding, thereby decreasing β-catenin ubiquitination levels to abolish its proteasomal degradation. Importantly, SHARPIN is required for invasiveness and malignant growth of gastric cancer cells in vitro and in vivo, a function that is largely dependent on its binding partner β-catenin. In line with these findings, elevated expression of SHARPIN in gastric cancer tissues is associated with disease malignancy and correlates with β-catenin expression levels. CONCLUSIONS: Our findings reveal a novel molecular link connecting linear ubiquitination machinery and Wnt/β-catenin signaling via SHARPIN-mediated stabilization of β-catenin. Targeting the linear ubiquitination-independent function of SHARPIN could be exploited to inhibit the hyperactive β-catenin signaling in a subset of human gastric cancers.
Entities:
Keywords:
Gastric cancer; Linear ubiquitination; SHARPIN; Wnt/β-catenin signaling