Investigating the regulation of brain-specific kinases 1 and 2 by phosphorylation.
Brain-specific kinases 1 and 2 (BRSK1/2) are AMP-activated protein kinase (AMPK)-related kinases that are highly expressed in mammalian forebrain. Studies using transgenic animal models have implicated a role for these kinases in the establishment of neuronal polarity. BRSK1 and BRSK2 are activated by phosphorylation of a threonine residue in the T-loop activation segment of the kinase domain. In vitro studies have demonstrated that LKB1, an upstream kinase in the AMPK cascade, can catalyze this phosphorylation. However, to date, a detailed comparative analysis of the molecular regulation of BRSK1/2 has not been undertaken. Here we present evidence that excludes another upstream kinase in the AMPK cascade, Ca(2+)/calmodulin-dependent protein kinase kinase beta, from a role in activating BRSK1/2. We show that equivalent mutations in the ubiquitin-associated domains of the BRSK isoforms produce differential effects on the activation of BRSK1 and BRSK2. Contrary to previous reports, activation of cAMP-dependent protein kinase does not affect BRSK1 or BRSK2 activity in mammalian cells. Furthermore, stimuli that activate AMPK had no effect on BRSK1/2. Finally, we provide evidence suggesting that protein phosphatase 2C is a likely candidate for catalyzing the dephosphorylation and inactivation of BRSK1/2.
Bright
Nicola J
NJ
Medical Research Council Cellular Stress Group, MRC Clinical Sciences Centre, Du Cane Road, London, United Kingdom.
Carling
David
D
Thornton
Claire
C
D000091162:AMP-Activated Protein Kinase Kinases; D000818:Animals; D054729:Calcium-Calmodulin-Dependent Protein Kinase Type 1; D002460:Cell Line; D004789:Enzyme Activation / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D016548:Prosencephalon / Q000201:enzymology; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D000071636:Protein Phosphatase 2C; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000502:physiology; D011817:Rabbits
D047908:Intracellular Signaling Peptides and Proteins; D007527:Isoenzymes; D011494:Protein Kinases; C523084:BRSK1 protein, human; C507732:Brsk2 protein, human; D017346:Protein Serine-Threonine Kinases; C109790:STK11 protein, human; D054729:Calcium-Calmodulin-Dependent Protein Kinase Type 1; D000091162:AMP-Activated Protein Kinase Kinases; C000607456:PPM1A protein, human; C000607457:PPM1B protein, human; C000607460:PPM1G protein, human; D010749:Phosphoprotein Phosphatases; D000071636:Protein Phosphatase 2C