Interleukin-1 stimulated activation of the COT catalytic subunit through the phosphorylation of Thr290 and Ser62

The protein kinase COT/Tpl2 is activated by interleukin-1 (IL-1), TNF alpha and lipopolysaccharide, and its activation by these agonists involves the I kappa B kinase beta (IKK beta) catalysed phosphorylation of the p105 regulatory subunit. Here, we show that COT activation also requires catalytic subunit phosphorylation, since IL-I beta induced a 5-10-fold activation of a COT mutant unable to bind p105. Activation was paralleled by the phosphorylation of Thr290 and Ser62 and unaffected by the IKK beta inhibitor PS1145 at concentrations which prevented the degradation of I kappa B alpha. Mutagenesis experiments indicated that COT activation is initiated by Thr290 phosphorylation catalysed by an IL-1stimulated protein kinase distinct from IKK beta, while Ser62 phosphorylation is an autophosphorylation event required for maximal activation. (c) 2006 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.