Model studies of transmembrane interaction of FcEpsilonRIAlpha/FcRGamma reveal novel strategies to inhibit allergic responses

ABSTRACT

The high-affinity IgE receptor complex plays an essential part in allergic responses and involved in downstream signaling, released inflammatory mediators that cause allergic responses. The transmembrane region of the high-affinity IgE has a conserved motif [LFAVDTGL] where a polar aspartate [D194] is important for the ligand binding. This modeling study proposes novel potential binding sites between high affinity immunoglobulin E receptor Alpha subunit [FcEpsilonRIAlpha] and FcRGamma and as a consequence, we propose a new model of FcEpsilonRIAlpha and FcRGamma interaction [T194] which can mediate downstream signaling in allergic response. The docking of FcRGamma with wild-type [D194] and mutant human high affinity immunoglobulin E receptor Alpha subunit [D194T, D194I, D194L, D194A, D194V, D194E, D194S and D194R] has been performed on Autodock Vina. This modeling study is based on lab data obtained by carrying out sitedirected mutagenesis done at residue D194 of FcEpsilonRIAlpha to assess its functional importance for the mediation of intracellular signal cascade. HuFcEpsilonRIAlpha D194 residue was replaced with threonine, leucine, serine, arginine, alanine, asparagine and glutamic acid. FcRGamma docking on mutated huFcEpsilonRIAlpha [D194T] indicated a new site of interaction and emphasizes the significance of the charge and size of an amino acid at position 194 in huFcEpsilonRIAlpha subunit. Amino acids D and T at position 194 are important for cell surface localization, interactions, distribution and downstream signaling of IgE receptor subunit. These proposed models may herald in better therapeutic interventions to combat unfavorably allergic diseases