4-Aminoethylamino-emodin--a novel potent inhibitor of GSK-3beta--acts as an insulin-sensitizer avoiding downstream effects of activated beta-catenin.
Glycogen synthase kinase-3beta (GSK-3beta) is a key target and effector of downstream insulin signalling. Using comparative protein kinase assays and molecular docking studies we characterize the emodin-derivative 4-[N-2-(aminoethyl)-amino]-emodin (L4) as a sensitive and potent inhibitor of GSK-3beta with peculiar features. Compound L4 shows a low cytotoxic potential compared to other GSK-3beta inhibitors determined by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide assay and cellular ATP levels. Physiologically, L4 acts as an insulin-sensitizing agent that is able to enhance hepatocellular glycogen and fatty acid biosynthesis. These functions are particularly stimulated in the presence of elevated concentrations of glucose and in synergy with the hormone action at moderate but not high insulin levels. In contrast to other low molecular weight GSK-3beta inhibitors (SB216763 and LiCl) or Wnt-3alpha-conditioned medium, however, L4 does not induce reporter and target genes of activated beta-catenin such as TOPflash, Axin2 and glutamine synthetase. Moreover, when present together with SB216763 or LiCl, L4 counteracts expression of TOPflash or induction of glutamine synthetase by these inhibitors. Because L4 slightly activates beta-catenin on its own, these results suggest that a downstream molecular step essential for activation of gene transcription by beta-catenin is also inhibited by L4. It is concluded that L4 represents a potent insulin-sensitizing agent favouring physiological effects of insulin mediated by GSK-3beta inhibition but avoiding hazardous effects such as activation of beta-catenin-dependent gene expression which may lead to aberrant induction of cell proliferation and cancer.
Gebhardt
Rolf
R
Institute of Biochemistry, Medical Faculty, University of Leipzig, Leipzig, Germany. rgebhardt@medizin.uni-leipzig.de
Lerche
Katja S
KS
Götschel
Frank
F
Günther
Robert
R
Kolander
Jens
J
Teich
Lars
L
Zellmer
Sebastian
S
Hofmann
Hans-Jörg
HJ
Eger
Kurt
K
Hecht
Andreas
A
Gaunitz
Frank
F
D000818:Animals; D060466:Axin Protein; D047390:Casein Kinase II / Q000037:antagonists & inhibitors / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism; D004642:Emodin / Q000031:analogs & derivatives / Q000737:chemistry / Q000494:pharmacology*; D005227:Fatty Acids / Q000096:biosynthesis; D006003:Glycogen / Q000378:metabolism; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D022781:Hepatocytes / Q000187:drug effects / Q000201:enzymology; D006801:Humans; D020128:Inhibitory Concentration 50; D007328:Insulin / Q000494:pharmacology*; D051379:Mice; D008954:Models, Biological; D008958:Models, Molecular; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D055550:Protein Stability / Q000187:drug effects; D051381:Rats; D051820:TCF Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D051176:beta Catenin / Q000378:metabolism*
C552996:4-aminoethylamino-emodin; D060466:Axin Protein; C111729:Axin2 protein, mouse; D003598:Cytoskeletal Proteins; D005227:Fatty Acids; D007328:Insulin; D047428:Protein Kinase Inhibitors; D051820:TCF Transcription Factors; D051176:beta Catenin; D006003:Glycogen; D047390:Casein Kinase II; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; C000605508:Gsk3b protein, rat; D038362:Glycogen Synthase Kinase 3; D004642:Emodin