Functional redundancy of GSK-3alpha and GSK-3beta in Wnt/beta-catenin signaling shown by using an allelic series of embryonic stem cell lines.
In mammalian cells, glycogen synthase kinase-3 (GSK-3) exists as two homologs, GSK-3alpha and GSK-3beta, encoded by independent genes, which share similar kinase domains but differ substantially in their termini. Here, we describe the generation of an allelic series of mouse embryonic stem cell (ESC) lines with 0-4 functional GSK-3 alleles and examine GSK-3-isoform function in Wnt/beta-catenin signaling. No compensatory upregulation in GSK-3 protein levels or activity was detected in cells lacking either GSK-3alpha or GSK-3beta, and Wnt/beta-catenin signaling was normal. Only in cells lacking three or all four of the alleles was a gene-dosage effect on beta-catenin/TCF-mediated transcription observed. Indeed, GSK-3alpha/beta double-knockout ESCs displayed hyperactivated Wnt/beta-catenin signaling and were severely compromised in their ability to differentiate, but could be rescued to normality by re-expression of functional GSK-3. The rheostatic regulation of GSK-3 highlights the importance of considering the contributions of both homologs when studying GSK-3 functions in mammalian systems.
Doble
Bradley W
BW
Samuel Lunenfeld Research Institute, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario M5G 1X5, Canada.
Patel
Satish
S
Wood
Geoffrey A
GA
Kockeritz
Lisa K
LK
Woodgett
James R
JR
D000818:Animals; D002460:Cell Line; D003600:Cytosol / Q000378:metabolism; D004622:Embryo, Mammalian / Q000166:cytology / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D038362:Glycogen Synthase Kinase 3 / Q000235:genetics / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D049452:Green Fluorescent Proteins / Q000378:metabolism; D051379:Mice; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013234:Stem Cells / Q000378:metabolism; D051153:Wnt Proteins / Q000235:genetics / Q000378:metabolism*; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism*
D051153:Wnt Proteins; D051176:beta Catenin; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; D038362:Glycogen Synthase Kinase 3; C448021:glycogen synthase kinase 3 alpha