Rcan1 negatively regulates FcεRI-mediated signaling and mast cell function

Aggregation of the high affinity IgE receptor (FcεRI) activates a cascade of signaling events leading to mast cell activation. Subsequently, inhibitory signals are engaged for turning off activating signals. We identified that regulator of calcineurin (Rcan) 1 serves as a negative regulator for turning off FcεRI-mediated mast cell activation. FcεRI-induced Rcan1 expression was identified by suppression subtractive hybridization and verified by real-time quantitative polymerase chain reaction and Western blotting. Deficiency of Rcan1 led to increased calcineurin activity, increased nuclear factor of activated T cells and nuclear factor κB activation, increased cytokine production, and enhanced immunoglobulin E–mediated late-phase cutaneous reactions. Forced expression of Rcan1 in wild-type or Rcan1-deficient mast cells reduced FcεRI-mediated cytokine production. Rcan1 deficiency also led to increased FcεRI-mediated mast cell degranulation and enhanced passive cutaneous anaphylaxis. Analysis of the Rcan1 promoter identified a functional Egr1 binding site. Biochemical and genetic evidence suggested that Egr1 controls Rcan1 expression. Our results identified Rcan1 as a novel inhibitory signal in FcεRI-induced mast cell activation and established a new link of Egr1 and Rcan1 in FcεRI signaling.