title: Ca2+/Calmodulin-dependent protein kinase kinase beta is regulated by multisite phosphorylation.
abstract: Ca(2+)/calmodulin-dependent protein kinase kinase β (CaMKKβ) is a serine/threonine-directed kinase that is activated following increases in intracellular Ca(2+). CaMKKβ activates Ca(2+)/calmodulin-dependent protein kinase I, Ca(2+)/calmodulin-dependent protein kinase IV, and the AMP-dependent protein kinase in a number of physiological pathways, including learning and memory formation, neuronal differentiation, and regulation of energy balance. Here, we report the novel regulation of CaMKKβ activity by multisite phosphorylation. We identify three phosphorylation sites in the N terminus of CaMKKβ, which regulate its Ca(2+)/calmodulin-independent autonomous activity. We then identify the kinases responsible for these phosphorylations as cyclin-dependent kinase 5 (CDK5) and glycogen synthase kinase 3 (GSK3). In addition to regulation of autonomous activity, we find that phosphorylation of CaMKKβ regulates its half-life. We find that cellular levels of CaMKKβ correlate with CDK5 activity and are regulated developmentally in neurons. Finally, we demonstrate that appropriate phosphorylation of CaMKKβ is critical for its role in neurite development. These results reveal a novel regulatory mechanism for CaMKKβ-dependent signaling cascades.
authors.affiliation: Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA.
authors.forename: Michelle F
authors.initials: MF
authors.lastname: Green
authors.forename: John W
authors.initials: JW
authors.lastname: Scott
authors.forename: Rohan
authors.initials: R
authors.lastname: Steel
authors.forename: Jonathan S
authors.initials: JS
authors.lastname: Oakhill
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Kemp
authors.forename: Anthony R
authors.initials: AR
authors.lastname: Means
mesh_terms: D000818:Animals; D019556:COS Cells; D054737:Calcium-Calmodulin-Dependent Protein Kinase Kinase / Q000235:genetics / Q000378:metabolism*; D002522:Chlorocebus aethiops; D051360:Cyclin-Dependent Kinase 5 / Q000235:genetics / Q000378:metabolism; D038362:Glycogen Synthase Kinase 3 / Q000235:genetics / Q000378:metabolism; D006207:Half-Life; D006801:Humans; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D016501:Neurites / Q000201:enzymology*; D010766:Phosphorylation / Q000502:physiology; D017434:Protein Structure, Tertiary; D051381:Rats; D015398:Signal Transduction / Q000502:physiology
chemical_list: D009419:Nerve Tissue Proteins; D051360:Cyclin-Dependent Kinase 5; C517698:CAMKK2 protein, human; D054737:Calcium-Calmodulin-Dependent Protein Kinase Kinase; C517702:Camkk2 protein, rat; C495905:CDK5 protein, human; C495907:Cdk5 protein, rat; D038362:Glycogen Synthase Kinase 3