Bcl10 is phosphorylated on Ser138 by Ca2+/calmodulin-dependent protein kinase II

Ordered assembly of scaffold proteins Carma1–Bcl10–Malt1 determines NF-κB activation following T cell receptor (TCR) engagement. Carma1–Bcl10 interaction and the signaling pathway are controlled by Carma1 phosphorylation, which are induced by PKCθ and Ca2+/calmodulin-dependent protein kinase II (CaMKII). In addition to Carma1 phosphorylation, previous studies have demonstrated that Bcl10 is phosphorylated in the C-terminal Ser/Thr rich region following TCR engagement. However the kinases that phosphorylate Bcl10 are incompletely understood. Here we show that CaMKII phosphorylates Bcl10 on Ser138. Furthermore, a CaMKII inhibitor, KN93, and CaMKII siRNA substantially reduce Bcl10 phosphorylation induced by phorbol myristate acetate/ionomycin. S138A mutation prolongs Bcl10-induced NF-κB activation, suggesting that Bcl10 phosphorylation is involved in attenuation of NF-κB activation. These findings suggest that CaMKII modulates NF-κB activation via phosphorylating Bcl10 as well as Carma1.