title: GSK-3β controls autophagy by modulating LKB1-AMPK pathway in prostate cancer cells.
abstract: BACKGROUND
  Glycogen synthase kinase 3β (GSK3B, GSK-3β) is a multi-functional protein kinase involved in various cellular processes and its activity elevates after serum deprivation. We have shown that inhibition of GSK-3β activity triggered a profound autophagic response and subsequent necrotic cell death after serum deprivation in prostate cancer cells. In this study, we dissected the mechanisms involved in GSK-3β inhibition-triggered autophagy.
  
  
  METHODS
  Prostate cancer PC-3 and DU145 cells were used in the study. Multiple GSK-3β specific inhibitors were used including small chemicals TDZD8, Tideglusib, TWS119, and peptide L803-mts. Western blot assay coupled with phospho-specific antibodies were used in detecting signal pathway activation. ATP levels were assessed with ATPLite kit and HPLC methods. Autophagy response was determined by evaluating Microtubule-associated proteins 1A/1B light chain 3B (LC3B) processing and p62 protein stability in Western blot assays. Immunofluorescent microscopy was used to detect LKB1 translocation.
  
  
  RESULTS
  Inhibition of GSK-3β activity resulted in a significant decline of cellular ATP production, leading to a significant increase of AMP/ATP ratio, a strong trigger of AMP-activated protein kinase (AMPK) activation in prostate cancer PC-3 cells. In parallel with increased LC-3B biosynthesis and p62 protein reduction, the classical sign of autophagy induction, AMPK was activated after inhibition of GSK-3β activity. Further analysis revealed that Liver kinase B1 (LKB1) but not Calcium/calmodulin-dependent protein kinase kinase β (CaMKKβ) is involved in AMPK activation and autophagy induction triggered by GSK-3β inhibition. Meanwhile, GSK-3β inhibition promoted LKB1 translocation from nuclear to cytoplasmic compartment and enhanced LKB1 interaction with its regulatory partners Mouse protein-25 (MO25) and STE20-related adaptor (STRAD).
  
  
  CONCLUSIONS
  In conclusion, our data suggest that GSK-3β plays an important role in controlling autophagy induction by modulating the activation of LKB1-AMPK pathway after serum deprivation.
authors.affiliation: Department of Pathology, Shaoxing University School of Medicine, Shaoxing, China.|Department of Urology, University of Kansas Medical Center, Kansas City, Kansas.
authors.forename: Aijing
authors.initials: A
authors.lastname: Sun
authors.affiliation: Department of Urology, University of Kansas Medical Center, Kansas City, Kansas.
authors.forename: Changlin
authors.initials: C
authors.lastname: Li
authors.affiliation: Department of Urology, University of Kansas Medical Center, Kansas City, Kansas.
authors.forename: Ruibao
authors.initials: R
authors.lastname: Chen
authors.affiliation: Department of Urology, University of Kansas Medical Center, Kansas City, Kansas.|Department of Pathology, China Three Gorges University College of Medicine, Yichang, China.
authors.forename: Yiling
authors.initials: Y
authors.lastname: Huang
authors.affiliation: Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, Kansas City, Kansas.
authors.forename: Qi
authors.initials: Q
authors.lastname: Chen
authors.affiliation: Department of Clinical Immunology and Rheumatology, Yichang Renmin Hospital, China Three Gorges University, Yichang, China.
authors.forename: Xiangjun
authors.initials: X
authors.lastname: Cui
authors.affiliation: Department of Internal Medicine and Kidney Institute, The Affiliated Hospital, Guangdong Medical College, Zhanjiang, China.
authors.forename: Huafeng
authors.initials: H
authors.lastname: Liu
authors.affiliation: Department of Urology, University of Kansas Medical Center, Kansas City, Kansas.
authors.forename: J Brantley
authors.initials: JB
authors.lastname: Thrasher
authors.affiliation: Department of Urology, University of Kansas Medical Center, Kansas City, Kansas.|Department of Pathology, China Three Gorges University College of Medicine, Yichang, China.|Department of Clinical Immunology and Rheumatology, Yichang Renmin Hospital, China Three Gorges University, Yichang, China.|Department of Internal Medicine and Kidney Institute, The Affiliated Hospital, Guangdong Medical College, Zhanjiang, China.
authors.forename: Benyi
authors.initials: B
authors.lastname: Li
mesh_terms: D000091162:AMP-Activated Protein Kinase Kinases; D055372:AMP-Activated Protein Kinases / Q000502:physiology*; D000818:Animals; D001343:Autophagy / Q000187:drug effects / Q000502:physiology*; D045744:Cell Line, Tumor; D004791:Enzyme Inhibitors / Q000494:pharmacology; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors / Q000502:physiology*; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D008297:Male; D051379:Mice; D011471:Prostatic Neoplasms / Q000378:metabolism* / Q000473:pathology; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*
chemical_list: D004791:Enzyme Inhibitors; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; D017346:Protein Serine-Threonine Kinases; C109790:STK11 protein, human; D038362:Glycogen Synthase Kinase 3; D000091162:AMP-Activated Protein Kinase Kinases; D055372:AMP-Activated Protein Kinases
keywords: AMPK; GSK-3β; LKB1; autophagy; serum deprivation