Folate Receptor Beta Regulates Macrophage NLRP3 Inflammasome Activation and Pyroptosis in a Folate-Independent Manner

Folate receptor beta (FRb), encoded by FOLR2, is selectively expressed in monocytes and macrophages, yet its function in innate immune signaling remains poorly defined. Here, we identify FRb as a novel regulator of NLRP3 inflammasome activation and pyroptosis in human THP-1 macrophages. Using CRISPR/Cas9-mediated gene deletion, we show that loss of FOLR2 impairs caspase-1 activation, gasdermin D cleavage, and IL-1b release in response to multiple NLRP3 stimuli, without altering pro-IL-1 b induction. These defects were not rescued by exogenous folate and were independent of extracellular folate concentrations. Mechanistically, FOLR2 deletion reduced potassium efflux and downregulated multiple potassium channel genes. Single-cell RNA sequencing revealed broad transcriptional repression in FRb-deficient macrophages, including genes involved in inflammasome signaling and ion transport. Genome-wide methylation profiling showed increased CpG hypermethylation in FOLR2-deficient cells, consistent with reduced transcriptional activity. Our findings indicate that FRb promotes NLRP3 activation in a folate-independent manner by regulating transcription and K⁺ efflux in macrophages. These data reveal a previously unrecognized immunoregulatory role for FRb with implications for host defense, autoimmunity, and macrophage function in tissue microenvironments such as the tumor or placenta.