Rcan1 negatively regulates FcεRI-mediated signaling and mast cell function

Aggregation of the high affinity IgE receptor (Fc epsilon RI) 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 Fc epsilon RI-mediated mast cell activation. Fc epsilon RI-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 kappa B 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 Fc epsilon RI-mediated cytokine production. Rcan1 deficiency also led to increased Fc epsilon RI-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 Fc epsilon RI-induced mast cell activation and established a new link of Egr1 and Rcan1 in Fc epsilon RI signaling.