title: Chloroquine Increases Glucose Uptake via Enhancing GLUT4 Translocation and Fusion with the Plasma Membrane in L6 Cells.
abstract: OBJECTIVE
  Chloroquine can induce an increase in the cellular uptake of glucose; however, the underlying mechanism is unclear.
  
  
  METHODS
  In this study, translocation of GLUT4 and intracellular Ca2+ changes were simultaneously observed by confocal microscope in L6 cells stably over-expressing IRAP-mOrange. The GLUT4 fusion with the plasma membrane (PM) was traced using HA-GLUT4-GFP. Glucose uptake was measured using a cell-based glucose uptake assay. GLUT4 protein was detected by Western blotting and mRNA level was detected by RT-PCR.
  
  
  RESULTS
  We found that chloroquine induced significant increases in glucose uptake, glucose transporter GLUT4 translocation to the plasma membrane (GTPM), GLUT4 fusion with the PM, and intracellular Ca2+ in L6 muscle cells. Chloroquine-induced increases of GTPM and intracellular Ca2+ were inhibited by Gallein (Gβx03B3; inhibitor) and U73122 (PLC inhibitor). However, 2-APB (IP3R blocker) only blocked the increase in intracellular Ca2+ but did not inhibit GTPM increase. These results indicate that chloroquine, via the Gβx03B3;-PLC-IP3-IP3R pathway, induces elevation of Ca2+, and this Ca2+ increase does not play a role in chloroqui-ne-evoked GTPM increase. However, GLUT4 fusion with the PM and glucose uptake were significantly inhibited with BAPTA-AM. This suggests that Ca2+ enhances GLUT4 fusion with the PM resulting in glucose uptake increase.
  
  
  CONCLUSIONS
  Our data indicate that chloroquine via Gβx03B3;-PLC-IP3-IP3R induces Ca2+ elevation, which in turn promotes GLUT4 fusion with the PM. Moreover, chloroquine can enhance GLUT4 trafficking to the PM. These mechanisms eventually result in glucose uptake increase in control and insulin-resistant L6 cells. These findings suggest that chloroquine might be a potential drug for improving insulin tolerance in diabetic patients.
authors.forename: Qi
authors.initials: Q
authors.lastname: Zhou
authors.forename: Xinzhou
authors.initials: X
authors.lastname: Yang
authors.forename: Mingrui
authors.initials: M
authors.lastname: Xiong
authors.forename: Xiaolan
authors.initials: X
authors.lastname: Xu
authors.forename: Li
authors.initials: L
authors.lastname: Zhen
authors.forename: Weiwei
authors.initials: W
authors.lastname: Chen
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
authors.forename: Jinhua
authors.initials: J
authors.lastname: Shen
authors.forename: Ping
authors.initials: P
authors.lastname: Zhao
authors.forename: Qing-Hua
authors.initials: QH
authors.lastname: Liu
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000187:drug effects*; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D002738:Chloroquine / Q000494:pharmacology*; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism*; D051275:Glucose Transporter Type 4 / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D060888:Real-Time Polymerase Chain Reaction
chemical_list: D051275:Glucose Transporter Type 4; D012333:RNA, Messenger; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D004533:Egtazic Acid; D002738:Chloroquine; D005947:Glucose; D002118:Calcium