日本質量分析学会 第70回質量分析総合討論会会

演題概要

ポスター発表

第3日 6月24日(金)  P会場(501,502,503)

水素/重水素交換質量分析とクロスリンク質量分析を用いたFcγRIIIaおよび抗原との結合におけるIgGの構造解析

(1阪大院工2ExCELLS3分子研4名市大院薬5サーモフィッシャー)
o山口祐希1若泉なつみ1入佐充音1丸野孝浩1嶋田麻里1新谷晃也1西海遥夏1與語理那2,3,4谷中冴子2,3,4肥後大輔5鳥巣哲生1加藤晃一2,3,4内山進1,2

The interaction between immunoglobulin G1 (IgG1) and Fc gamma receptor IIIa (FcγRIIIa) is essential for mediating immune responses. IgG1 is composed of two Fab portions and one Fc portion. FcγRIIIa is expressed primarily on natural killer cells and consists of two extracellular domains: the membrane-distal domain (D1) and membrane-proximal domain (D2). Recent studies have shown that Fab and Fc are involved in IgG-FcγRIII interactions. Here, we conducted hydrogen/deuterium exchange mass spectrometry (HDX-MS) and crosslinking mass spectrometry (XL-MS) to clarify the interaction sites and structural changes upon formation of IgG-FcγRIII complexes using marketed therapeutic antibodies. Moreover, the influence of antigen-binding on IgG-FcγRIII interactions was investigated by HDX-MS. Combined HDX-MS and XL-MS revealed that the CL domain of Fab was in close proximity to FcγRIIIa, indicating that this domain specifically interacts with D1 and D2 of FcγRIIIa. The decreases in deuterium uptake of the segments in the CH1 may represent another interacting region with FcγRIIIa. Moreover, our HDX-MS detected the structural alterations in CH3 caused by FcγRIIIa-binding and the structural alterations in Fab caused by antigen-binding, which potentially facilitate the stabilization and clusterization of antigen-IgG-FcγRIII complexes for the subsequent activation of immune cells.