The A subunit of the high affinity IgE receptor (Fce RIA or FceRIA) is an IgE-binding type I transmembrane glycoprotein of the multichain immune recognition (MIRR) family. The receptor, Fce RI, is a tetrameric complex of oneA, one B and two G subunits (ABG2) on mast cells and basophils. An alternate trimeric form (AB2) is expressed on human, but not rodent, mast cells, basophils, eosinophils and professional antigen presenting cells. While the G subunit is essential for expression of Fce RIA on the cell surface and for cell signaling, the B subunit, when present, increases the halflife of the Fce RI complex on the cell surface. An isoform of the B subunit, BT, blocks processing of the A subunit and its cell surface expression. Human Fce RIA cDNA encodes 257aa including a 25aa signal sequence, a 180aa extracellular domain containing two Ig-like domains that bind IgE and an endoplasmic reticulum retention motif, a 21aa transmembrane domain with a charged aa (Asp219) that contributes to intracellular transport, and a 32aa cytoplasmic sequence. Human Fce RIA shares 50-62% aa sequence identity with mouse, rat, equine, ovine, bovine, porcine and canine Fce RIA. Binding of IgE alone increases surface expression of Fce RI, while crosslinking of IgE/Fce RI complexes by IgE ligands (allergens) initiates receptor internalization and signaling. Mast cell and basophil activation by IgE/Fce RI crosslinking causes degranulation, releasing histamine, leukotrienes, prostaglandins, and other mediators of immediate-type and late-phase allergic reactions. Circulating autoantibodies that crosslink Fce RIA are often found in patients with chronic urticaria. Fce RIA on human antigen presenting cells mediates uptake and processing of allergens for presentation by class II MHC. Fc epsilon RI expression on human DC and Langerhans cells is up-regulated during allergic reactions (atopy) and correlates with serum IgE concentration.
Recombinant protein corresponding to Val26-Gln205 fused to 6X His-Tag at C-terminal expressed in mouse myeloma cell line, NS0.
Molecular Weight:~21.9kD
Biological Activity:Measured by its binding ability in a functional ELISA. When recombinant human Fce RIA is immobilized at 2ug/ml (100ul/well), the concentration of human IgE that produces 50% of the optimal binding response is found to be ~0.05-0.2ug/ml.
Storage and Stability:Lyophilized and reconstituted products are stable for 6 months after receipt at -20°C. Reconstitute with sterile PBS. Aliquot to avoid repeated freezing and thawing. Store at -20°C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer.
