Fc Epsilon RI Signaling Pathway

1. Fc Epsilon RI Signaling Pathway Fc epsilon RI, also known as FcεRI, is a high-affinity receptor for IgE that binds to the Fc portion of IgE. Its structural characteristics are as follows: Fc ε heteromultimeric complex that is multiple strands of immunological recognition receptors. It exists in the form of an αβγ2 tetramer or an αγ2 trimer. The alpha subunit includes an extracellular region and a transmembrane region. The extracellular domain contains two near-membrane-end structural region that binds to the IgE Fc segment, and the other structural region that is involved in high-affinity binding. The alpha subunit contains seven glycosylation sites of N-chain that affect receptor secretion and stability. Further studies indicate that these glycosylation sites are not required for proper folding of the alpha chain and do not affect its binding to IgE. Additionally, the alpha subunit is a key site that triggers an allergic reaction. Studies by David et al. have confirmed that mice that remove the alpha subunit do not fully express Fc ε RI and have no IgE-mediated allergic reactions. RI is a immunoglobulin-like regions, the The beta subunit has a transmembrane region and an intracellular region. It is an antigenic receptor that penetrates the membrane four times and is now named as the MS4A gene family with CD20 and HTM4. Therefore, both the N-terminus and the C-terminus are in the cytoplasm; the N-terminus contains a characteristic proline, and its function is unknown; the C-terminus contains an immunoreceptor tyrosine activation motif (ITAM). The β subunit is a gamma subunit-mediated amplification of the Syk tyrosine kinase activation effect, which can amplify the activity of tyrosine kinase and calcium influx by 5 to 7 times, while itself has little or produces no signal transduction by crosslinking of FcεRI. Researchers find that the β subunit has a second amplification function, which is to amplify the expression of FcεRI on the cell surface. The above findings also provide a possible explanation for the large differences in the distribution density of FcεRI between different cells, such as the differential between β-negative cells (monocytes, dendritic cells) and β-positive cells (mast cells, basophils). The gamma subunit exists as a homodimer. Extracellularly, two gamma subunits are linked by a disulfide bond, and each has a transmembrane region. The intracellular region has an ITAM motif, and the gamma subunit belongs to the same family member with the TCR δ chain, which can be activated after cross-linking of Fc ε RI. Fc ε RI is required for cell membrane expression and intracellular signal transduction. https://www.creative-diagnostics.com/fc-epsilon-ri-signaling-pathway.htm