Calmodulin trimethylation by calmodulin-lysine N-methyltransferase plays an anti-inflammatory role by inhibiting caspase-11 noncanonical inflammasome in macrophages.

Noncanonical inflammasomes have recently emerged as critical regulators of macrophage-driven inflammatory responses, however, their molecular functions remain incompletely defined. Calmodulin (CaM)-lysine N-methyltransferase (CAMKMT) has been identified as a novel nonhistone protein methyltransferase responsible for CaM methylation, yet the contribution of CAMKMT-dependent CaM methylation to inflammatory responses has not been explored. In this study, we investigated the anti-inflammatory role of CAMKMT-mediated CaM methylation in caspase-11 noncanonical inflammasome-activated inflammatory responses in macrophages. Activation of the caspase-11 noncanonical inflammasome in J774A.1 macrophages markedly reduced CAMKMT expression, CaM trimethylation at lysine 116 (Tme-K), and the activation of the CaM-dependent kinases CaMKK2 and CaMKIV. Enforced expression of CAMKMT significantly attenuated caspase-11 noncanonical inflammasome-driven inflammatory responses and restored CaM Tme-K level and CaMKK2 and CaMKIV activation suppressed by inflammasome signaling. Similarly, CaM inhibited caspase-11 noncanonical inflammasome-mediated inflammatory responses, whereas CaM lysine 116 mutant (CaM K116A) abrogated CaMKK2 and CaMKIV activation and exacerbated inflammasome-driven inflammation in J774A.1 cells. In vivo, CaM conferred protection against LPS-induced acute lethal sepsis, as evidenced by improved survival, reduced murine sepsis scores, lower serum pro-inflammatory cytokine levels, and diminished pyroptotic cell death, in contrast, CaM K116A failed to provide such protection. Collectively, these findings identify the CAMKMT-CaM Tme-K axis as a critical anti-inflammatory regulator of caspase-11 noncanonical inflammasome-driven inflammatory responses in macrophages.