A noncatalytic domain of glycogen synthase kinase-3 (GSK-3) is essential for activity.
Glycogen synthase kinase-3 (GSK-3) isoforms, GSK-3alpha and GSK-3beta, are serine/threonine kinases involved in numerous cellular processes and diverse diseases, including Alzheimer disease, cancer, and diabetes. GSK-3 isoforms function redundantly in some settings, while, in others, they exhibit distinct activities. Despite intensive investigation into the physiological roles of GSK-3 isoforms, the basis for their differential activities remains unresolved. A more comprehensive understanding of the mechanistic basis for GSK-3 isoform-specific functions could lead to the development of isoform-specific inhibitors. Here, we describe a structure-function analysis of GSK-3alpha and GSK-3beta in mammalian cells. We deleted the noncatalytic N and C termini in both GSK-3 isoforms and generated point mutations of key regulatory residues. We examined the effect of these mutations on GSK-3 activity toward Tau, activity in Wnt signaling, interaction with Axin, and GSK-3alpha/beta Tyr(279/216) phosphorylation. We found that the N termini of both GSK-3 isoforms were dispensable, whereas progressive C-terminal deletions resulted in protein misfolding exhibited by deficient activity, impaired ability to interact with Axin, and a loss of Tyr(279/216) phosphorylation. Our data predict that small molecules targeting the divergent C terminus may lead to isoform-specific GSK-3 inhibition through destabilization of the GSK-3 structure.
Buescher
Jessica L
JL
Integrated Biomedical Science Graduate Program, College of Medicine, The Ohio State University, Columbus, Ohio 43210, USA.
Phiel
Christopher J
CJ
D060466:Axin Protein; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000502:physiology; D038362:Glycogen Synthase Kinase 3 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D007536:Isomerism; D007668:Kidney / Q000166:cytology; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D011392:Proline / Q000378:metabolism; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D014162:Transfection; D014443:Tyrosine / Q000378:metabolism; D051153:Wnt Proteins / Q000378:metabolism; D016875:tau Proteins / Q000378:metabolism
D060466:Axin Protein; C054369:MAPT protein, human; D012097:Repressor Proteins; D051153:Wnt Proteins; D016875:tau Proteins; D014443:Tyrosine; D011392:Proline; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D038362:Glycogen Synthase Kinase 3; C448021:glycogen synthase kinase 3 alpha