AKT-mediated phosphorylation of ZDHHC5 promotes NOD1 palmitoylation and innate immune signaling.

Introduction: Nucleotide-binding oligomerization domain 1 (NOD1) is an intracellular pattern recognition receptor that detects bacterial peptidoglycan and initiates innate immune responses through membrane-associated signaling complexes. NOD1 activation depends on ZDHHC5-mediated palmitoylation, which promotes its membrane recruitment. However, whether growth factors and insulin modulate this NOD1 activation remains poorly defined. Methods: We investigated the effects of growth factors and insulin on NOD1 signaling using biochemical and cell-based approaches. Protein phosphorylation and interactions were analyzed by immunoblotting, co-immunoprecipitation, and mutagenesis assays. NOD1 palmitoylation, membrane localization, and downstream signaling activities were evaluated following modulation of AKT signaling and ZDHHC5 phosphorylation. Results: We found that growth factors and insulin positively regulate NOD1 activation through an AKT-ZDHHC5-NOD1 signaling axis. Mechanistically, AKT directly phosphorylated the palmitoyltransferase ZDHHC5 at Ser345 and Ser380, promoting its retention at the plasma membrane and enhancing its enzymatic activity toward NOD1. AKT-dependent phosphorylation increased NOD1 palmitoylation and membrane recruitment, thereby facilitating activation of downstream innate immune signaling pathways. Discussion: These findings identify a previously unrecognized mechanism linking growth factor- and insulin-mediated AKT activation to innate immune signaling. AKT-dependent phosphorylation of ZDHHC5 promotes NOD1 palmitoylation and activation, revealing a positive regulatory axis that integrates metabolic cues with innate immune responses. The AKT-ZDHHC5 pathway may therefore represent a potential target for modulating NOD1- driven inflammatory diseases.