1. Dual degradation signals destruct GLI1: AMPK inhibits GLI1 through β-TrCP-mediated proteasome degradation
- Author
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Yen Hsing Li, Chun Ju Chang, Jer Yen Yang, Rui Zhang, GuangJun Zhang, Wei Hsuan Hsu, Kay Ka Wai Li, and Sherri Y. Huang
- Subjects
AMPK ,0301 basic medicine ,Proteasome Endopeptidase Complex ,medicine.medical_specialty ,Cellular pathology ,Beta-Transducin Repeat-Containing Proteins ,GLI1 ,Active Transport, Cell Nucleus ,Gene Expression ,AMP-Activated Protein Kinases ,medulloblastoma ,Zinc Finger Protein GLI1 ,Mice ,03 medical and health sciences ,Ubiquitin ,AMP-activated protein kinase ,Cell Line, Tumor ,Neoplasms ,Internal medicine ,β-transducin repeat containing protein (β-TrCP) ,medicine ,Animals ,Humans ,Phosphorylation ,Cell Proliferation ,integumentary system ,biology ,Ubiquitination ,beta-Transducin Repeat-Containing Proteins ,Hedgehog signaling pathway ,3. Good health ,Cell biology ,Protein Transport ,030104 developmental biology ,Endocrinology ,Oncology ,Proteolysis ,biology.protein ,Signal transduction ,Hedgehog ,Research Paper ,Signal Transduction - Abstract
// Rui Zhang 1, * , Sherri Y. Huang 1, * , Kay Ka-Wai Li 2 , Yen-Hsing Li 1 , Wei-Hsuan Hsu 1 , Guang Jun Zhang 3, 4 , Chun-Ju Chang 1, 3 and Jer-Yen Yang 1, 3 1 Department of Basic Medical Sciences, West Lafayette, Indiana, USA 2 5/F of Cancer Centre, Prince of Wales Hospital, Department of Anatomical and Cellular Pathology, The Chinese University of Hong Kong, Shatin, Hong Kong 3 Center for Cancer Research, Purdue University, West Lafayette, Indiana, USA 4 Department of Comparative Pathobiology, Purdue University, West Lafayette, Indiana, USA * These authors contributed equally to this work Correspondence to: Jer-Yen Yang, email: jyyang@purdue.edu Keywords: AMPK, β-transducin repeat containing protein (β-TrCP), Hedgehog, GLI1, medulloblastoma Received: December 15, 2016 Accepted: April 05, 2017 Published: May 10, 2017 ABSTRACT Overexpression of the GLI1 gene has frequently been found in various cancer types, particularly in brain tumors, in which aberrant GLI1 induction promotes cancer cell growth. Therefore, identifying the molecular players controlling GLI1 expression is of clinical importance. Previously, we reported that AMPK directly phosphorylated and destabilized GLI1, resulting in the suppression of the Hedgehog signaling pathway. The current study not only demonstrates that AMPK inhibits GLI1 nuclear localization, but further reveals that β-TrCP plays an essential role in AMPK-induced GLI1 degradation. We found that activation of AMPK promotes the interaction between β-TrCP and GLI1, and induces β-TrCP-mediated GLI1-ubiquitination and degradation. Inhibiting AMPK activity results in the dissociation of the β-TrCP and GLI1 interaction, and diminishes β-TrCP-mediated-GLI1 ubiquitination and degradation. On GLI1, substitution of AMPK phosphorylation sites to aspartic acid (GLI1 3E ) results in stronger binding affinity of GLI1 with β-TrCP, accompanied by enhanced GLI1 ubiquitination and later degradation. In contrast, the GLI1 alanine mutant (GLI1 3A ) shows weaker binding with β-TrCP, which is accompanied by reduced β-TrCP-mediated ubiquitination and degradation. Together, these results demonstrate that AMPK regulates GLI1 interaction with β-TrCP by phosphorylating GLI1 and thus both post-translational modifications by AMPK and β-TrCP ultimately impact GLI1 degradation.
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- 2017