Redox regulation of brain selective kinases BRSK1/2: Implications for dynamic control of the eukaryotic AMPK family through Cys-based mechanisms

In eukaryotes, protein kinase signaling is regulated by a diverse array of
post-translational modifications (PTMs), including phosphorylation of
Ser/Thr residues and oxidation of cysteine (Cys) residues. While
regulation by activation segment phosphorylation of Ser/Thr residues is
well understood, relatively little is known about how oxidation of
cysteine residues modulate catalysis. In this study, we investigate redox
regulation of the AMPK-related Brain-selective kinases (BRSK) 1 and 2, and
detail how broad catalytic activity is directly regulated through
reversible oxidation and reduction of evolutionarily conserved Cys
residues within the catalytic domain. We show that redox-dependent control
of BRSKs is a dynamic and multilayered process involving oxidative
modifications of several Cys residues, including the formation of
intra-molecular disulfide bonds involving a pair of Cys residues near the
catalytic HRD motif and a highly conserved T-Loop Cys with a BRSK-specific
Cys within an unusual CPE motif at the end of the activation segment.
Consistently, mutation of the CPE-Cys increases catalytic activity in
vitro and drives phosphorylation of the BRSK substrate Tau in cells.
Molecular modeling and molecular dynamics simulations indicate that
oxidation of the CPE-Cys destabilizes a conserved salt bridge network
critical for allosteric activation. The occurrence of spatially proximal
Cys amino acids in diverse Ser/Thr protein kinase families suggests that
disulfide mediated control of catalytic activity may be a prevalent
mechanism for regulation within the broader AMPK family.