MAVS positively regulates mitochondrial integrity and metabolic fitness in antigen receptor-activated B cells

The role of mitochondrial homeostatic control in the metabolic remodeling associated with antigen receptor stimulation in B cells remains incompletely defined. Here we report that the mitochondrial antiviral signaling (MAVS) adaptor protein is involved in B cell receptor (BCR) initiated cellular proliferation and prolonged survival. MAVS is well known as a mitochondrial tethered signaling adaptor for sensing viral double-stranded RNA and type I interferon inducer. The role of MAVS downstream of BCR stimulation was recognized in absence of interferon, suggesting a new pathway for MAVS activation that is independent of viral infection. Mitochondria of BCR-activated MAVS-deficient B cells exhibited a damaged phenotype including disrupted mitochondrial morphology, excess mitophagy and the temporal progressive blunting of mitochondrial oxidative capacity with mitochondrial hyperpolarization and cell death. Co-stimulation with anti-CD40, in addition to BCR stimulation, corrected the proliferative gap between MAVS-deficient and -sufficient B cells; however, mitochondrial structural defects and functionality were only partially restored. Our data reveal a previously unrecognized role of MAVS in controlling mitochondrial homeostasis in response to BCR initiated B cell proliferation. Overall design: Comparative gene expression profiling analysis of RNA-seq data for