ABSTRACT
IgE-mediated cell signaling, induced by cross-linking of high affinity receptor for IgE [FepsilonRI] in the presence of antigen [Ag], is a well known mechanism described for mast cell activation in allergy and hypersensitivity reactions, which induces a spectrum of cellular responses such as secretion and up-regulation of cell surface FepsilonRL Although for several years IgE binding to FepsilonRI was considered to be a passive sensitization process, the outcomes of several recent studies have revealed a variety of different cellular responses to IgE binding compared to IgE plus Antigen binding. The present study applied a functional proteomics-based approach to investigate mast cell signaling events and provided new insights to FcsRI-mediated cell signaling in RBL-2H3.1 cells, and may point to the activation of alternative signaling pathways in response to IgE or IgE plus Ag. Comparative analysis by 2-D PAGE of RBL cells activated with IgE plus Ag for three and four hours compared to non-activated cells was followed by mass spectrometric protein identification and provided evidence for the induction of Stathmin 1 [STMN1] gene expression in response to IgE plus Ag activation. Complementary SDS-PAGE analysis showed a distinct up-regulation of STMN1 induction in response to challenge with IgE plus Ag compared to sensitization with IgE only. Phosphoproteomics analysis gave evidence for significant increase at phosphorylation of STMN1 on ser16 after 1min, though a slight rise at 5 min, and on ser38 after 1 and 5min sensitization with IgE and a similar result was observed for 1min IgE plus Ag-activation. IgE plus Ag-activation was also found to induce the phosphorylation of ser38 to a greater extent than sensitization with IgE. In contrast, IgE alone was more effective than IgE plus Ag at inducing phosphorylation of ser 16. Collectively this study provides further insights into the role of Stathmin 1 in FepsilonRI-mediated activation of cells of mast cell lineage and might shed light on the diverse response of these cells to IgE or IgE plus Ag