title: [APPL1-mediated effects of leptin on activity of GSK-3β in C2C12 cell].
abstract: OBJECTIVE
  To observe the effects of leptin on activity of GSK-3β and explore its mechanism.
  
  
  METHODS
  C2C12 myoblasts differentiated for 3 days into myotubes in differentiation medium. Myotubes were stimulated by leptin (100 nmol/L) for 0, 5, 15 or 30 min respectively. Western blot was used to detect the expression levels of GSK-3β and phospho-GSK-3β (ser-9). Co-immunoprecipitation (CO-IP) was performed to determine the relationship among APPL1, leptin receptor and GSK-3β in the presence or absence of leptin. The expression level of GSK-3β at phospho-GSK-3β (ser-9) was detected in APPL1-suppressed C2C12 myotube while that of APPL1 at phospho-APPL1 (ser-401) determined in GSK-3β overexpressed/inhibited C2C12 cell.
  
  
  RESULTS
  Leptin time-dependently increased the phosphorylation level of GSK-3β at ser-9 in C2C12 cell, and the pGSK-3β level in cells incubated by leptin for 30 min was as 4.08 times as which in control cells (P < 0.01). The triple complex of APPL1, leptin receptor and GSK-3β, in the presence of leptin, the binding capacity between APPL1 and GSK-3β was stronger. The level of phospho-GSK-3β was significantly lower in APPL1-suppressed C2C12 cell compared with that in control cells. And the phosphorylation of APPL1 at ser-401 could be induced by GSK-3β.
  
  
  CONCLUSIONS
  Leptin promotes muscle glycogen synthesis by inducing phosphorylation of GSK-3β in C2C12 cell. Such a function may be mediated by the triple complex of APPL1, leptin receptor and GSK-3β. Meanwhile, GSK-3β can also increase the phosphorylation of APPL1 at ser-401.
authors.affiliation: Department of Endocrinology & Metabolism, Shanghai Institute of Diabetes, Shanghai, China.
authors.forename: Miao
authors.initials: M
authors.lastname: Xu
authors.forename: Yuan-yuan
authors.initials: YY
authors.lastname: Xiao
authors.forename: Jun-feng
authors.initials: JF
authors.lastname: Han
authors.forename: Jun
authors.initials: J
authors.lastname: Yin
authors.forename: Jun-xi
authors.initials: JX
authors.lastname: Lu
authors.forename: Ruo-bing
authors.initials: RB
authors.lastname: Liu
authors.forename: Li
authors.initials: L
authors.lastname: Wei
authors.forename: Yu-qian
authors.initials: YQ
authors.lastname: Bao
authors.forename: Wei-ping
authors.initials: WP
authors.lastname: Jia
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D020738:Leptin / Q000494:pharmacology*; D051379:Mice; D032448:Myoblasts, Skeletal / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation; D054411:Receptors, Leptin / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C510733:Appl1 protein, mouse; D020738:Leptin; D054411:Receptors, Leptin; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; D038362:Glycogen Synthase Kinase 3