Architecture of the high-affinity immunoglobulin E receptor

Area of Science:

• Structural biology
• Immunology
• Biochemistry

Background:

• The high-affinity immunoglobulin E (IgE) receptor (FcεRI) is crucial for type I hypersensitivity reactions.
• FcεRI is a multimeric complex comprising α, β, and γ subunits, with IgE binding to the α subunit and signaling mediated by β and γ subunits via ITAMs.

Purpose of the Study:

• To determine the cryo-electron microscopy (cryo-EM) structures of the apo and Fcε-bound states of FcεRI.
• To elucidate the structural basis of FcεRI assembly and signaling.
• To identify potential species-specific differences in FcεRI structure and activation.

Main Methods:

• Cryo-electron microscopy (cryo-EM) was employed to visualize the FcεRI complex.
• Structural analysis focused on the transmembrane domain (TMD) and extracellular domains (ECDs).

Main Results:

• The apo and Fcε-bound FcεRI structures reveal a tightly packed αγ2 bundle within the TMD, assembling with the β subunit.
• Fcε binding does not induce significant conformational changes in the receptor.
• Species-specific differences in juxtamembrane interactions between mouse and human FcεRI were observed.

Conclusions:

• The study provides a structural framework for Fc receptor assembly and type I hypersensitivity signaling.
• Findings offer insights into the design of targeted antiallergic therapeutics.