Abstract
Upon FcεRI stimulation, mast cells secrete inflammatory cytokines and chemical mediators are related to allergic inflammation. FcεRI complex shows a tetrameric structure composed of three distinct polypeptides, which include the IgE-binding α chain, the four-folded membrane-spanning β chain, and the disulfide-linked γ- γ homodimer. The β chain acts as an amplifier for allergic reaction in mast cells. The β chain ITAM shows a notable depature from the consensus immunoreceptor tyrosine-based activation motif (ITAM) sequence with the presence of the third tyrosine between the two canonical tyrosines (YX5YX3Y). Our previous study revealed that degranulation and leukotriene production were impaired in cells expressing the mutated FcεRI β ITAM (FYY, YYF, FYF, FFF). However, cytokine production was enhanced in the YFY and FFF mutant. Here, we describe conformational studies of the C-terminal 43 peptide of wild type and mutated FcεRI β ITAM motifs FFF, FYF, YFY, FYY and YYF by circular dichroism(CD) spectroscopy. All of the far-UV CD spectra of WT, FFF, FYF, YFY, FYY, and YYF give typical α-helical feature. The temperature dependence of CD signal showed that midpoint temperature (Tm) decreased by almost 2 degree in FFF and YYF compared to that in WT. Near-UV CD of mutated FcεRI β chains are still ongoing. [J Physiol Sci. 2008;58 Suppl:S97]
