Regulation of GSK-3beta and beta-Catenin by Galphaq in HEK293T cells.
Recent studies have shown that heterotrimeric G proteins are involved in the regulation of the canonical Wnt/beta-Catenin pathway. However, the mechanism(s) behind this involvement is (are) poorly understood. Our previous results have shown that activation of Galphaq in Xenopus oocytes leads to inhibition of GSK-3beta and stabilization of the beta-Catenin protein, suggesting that Galphaq might stabilize beta-Catenin via inhibition of GSK-3beta. In this study, we have observed similar results in HEK293T cells. In these cells optimal activation of endogenous Galphaq by expressing M3-muscarinic acetylcholine receptor (with or without carbachol treatment), or exposing the cells to thrombin led to an increase of 2 to 3-fold in endogenous cytoplasmic beta-Catenin protein levels. In addition, expression of the activated mutant of Galphaq (GalphaqQL) dramatically enhanced accumulation of exogenous beta-Catenin with no effect on beta-catenin (CTNNB1) gene transcription. The Galphaq-mediated cellular accumulation of beta-Catenin was blocked by expression of a minigene encoding a Galphaq specific inhibitory peptide but not by a minigene encoding a Galphas blocking peptide. Also, expression of GalphaqQL led to a significant reduction in GSK-3beta kinase activity, supporting the idea that the positive role of Galphaq signaling in inducing cellular accumulation of beta-Catenin is mediated through inhibition of GSK-3beta.
Salmanian
Sara
S
Department of Cell & Molecular Biology, School of Biology, University College of Science, University of Tehran, Tehran, Iran.
Najafi
S Mahmoud A
SM
Rafipour
Maryam
M
Arjomand
Maryam Rezaei
MR
Shahheydari
Hamideh
H
Ansari
Sara
S
Kashkooli
Leily
L
Rasouli
S Javad
SJ
Jazi
Marie Saghaeian
MS
Minaei
Tayebeh
T
D002460:Cell Line; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000235:genetics / Q000378:metabolism*; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D043587:Receptor, Muscarinic M3 / Q000819:agonists / Q000096:biosynthesis; D014158:Transcription, Genetic; D051153:Wnt Proteins / Q000378:metabolism*; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism*
C495270:CTNNB1 protein, human; D043587:Receptor, Muscarinic M3; D051153:Wnt Proteins; D051176:beta Catenin; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D038362:Glycogen Synthase Kinase 3; D043802:GTP-Binding Protein alpha Subunits, Gq-G11