Investigating the regulation of brain specific kinases 1 & 2 by phosphorylation

Bright NJ, Carling D, Thornton C
Source: J Biol Chem
Publication Date: (2008)
Issue: 283(22): 14946-54
Research Area:
Cells used in publication:
Species: human
Tissue Origin: brain
Nucleofector® I/II/2b
Brain specific kinases 1 and 2 (BRSK1/2) are 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 AMP-activated protein kinase (AMPK) cascade, can catalyse 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, Ca2+/calmodulin dependent protein kinase kinase ss (CaMKKss), from a role in activating BRSK1/2. We show that equivalent mutations in the UBA 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 (PKA) 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 (PP2C) is a likely candidate for catalysing the dephosphorylation and inactivation of BRSK1/2.