O-Plex Pro Mouse 23-plex Group 1 Cytokine Assay (Bio-Rad, Hercules, CA) according to the manufacturer’s protocol. This assay detected 23 cytokines and chemokines including IL-1a, IL-1b, IL-2, IL-3, IL-4, IL-5, IL-6, IL-9, IL-10, IL-12 (p40), 22948146 IL-12 (p70), IL-13, IL-17A, TNF, Eotaxin, G-CSF, GM-CSF, IFNc, KC, CCL2, CCL3, CCL4, and CCL5. H, PGD2 production by STXBP1+/+ and STXBP12/2 FceRI-activated mast cells was measured using enzyme immunoassay kit. (n = 4 separate experiments). doi:10.1371/journal.pone.0058560.gproduction. STXBP1+/+ and STXBP12/2 mast cells produced similar amounts of PGD2 (Fig. 3H).STXBP1 Deficiency does not Affect IgE-dependent IkBNFkB Pathway Activation, MAP Kinase Phosphorylation, or Transcription Factor ActivationSignaling mechanisms regulated by various kinase proteins are thought to contribute to orchestrating intracellular trafficking during mast cell degranulation. STXBP1 itself is a target for phosphorylation that is required for membrane fusion in endothelial cells [44,45,46,47]. To determine whether STXBP1 plays a role in the signaling pathways initiated in mast cellsfollowing activation through FceRI, STXBP1+/+ and STXBP12/ LMCs were sensitized with anti-TNP IgE and stimulated with TNP-BSA. Cell lysates were analyzed by Western blotting to detect phospho- or total IkB, p38, JNK, ERK1/2, Akt, and PKG1. We did not observe major difference in the expression or phosphorylation of these proteins (Fig. 4A). Syntaxin-1 is a STXBP1 binding partner. Similarly, no major difference of syntaxin-1 was found between STXBP1+/+ and STXBP12/2 LMCs (Fig. 4A). Previous work in our lab has shown that Egr1 plays an important role in regulating mast cell activation and cytokine production [38,48,49]. To examine the effect of STXBPSTXBP1 Is Not Required for AllergyFigure 4. STXBP1 is not required for IkB-NFkB pathway activation, MAP kinase phosphorylation, or Egr and NFAT activity in FceRIactivated mast cells. A, STXBP1+/+ and STXBP12/2 mast cells were sensitized with anti-TNP IgE and stimulated with TNP-BSA (10 ng/ml) for various times. Whole cell lysates were analyzed by Western blotting for phospho-IkB and total IkB, phospho-p38 and total p38, phospho-JNK and total JNK, phospho-ERK1/2 and total ERK1/2, phospho-Akt and total Akt, Syntaxin-1, PKG-1, and Actin. B-D, STXBP1+/+ and STXBP12/2 mast cells were sensitized with anti-TNP IgE and stimulated with TNP-BSA (10 ng/ml) for various times. The 
nuclear proteins were isolated and subjected to EMSA. Egr binding consensus sequence (59-GGA TCC AGC GGG GGC GAG CGG GGG CGA ACG-39) (B), NF-kB binding consensus sequence (59-TTA TCA AAT GTG GGA TTT TCC CAT-39) from IL-6 promoter (C), and NFAT binding concensus sequence (59-AAG GTG TTT CCC CAA GCC TTT CCC-39) from IL-13 promoter (D) were labeled with 32P for EMSA. Shown is a representative from three independent experiments. doi:10.1371/journal.pone.0058560.gdeficiency on Egr1 transcriptional activity, LMCs from wild-type and STXBP12/2 mice were sensitized using anti-TNP IgE and stimulated with TNP-BSA for various times. Nuclear proteins of these LMCs were isolated and analyzed by EMSA using a 32Plabeled Egr family binding consensus sequence as a probe. STXBP1 deficiency showed no effect on Egr1 transcriptional activity (Fig. 4B). The pro-inflammatory transcription factors NFkB and NFAT also play an important role in the regulation of de novo synthesis of cytokines and chemokines following IgE-FceRI stimulation. We examined the effect of S.