Effects of anchor structure and glycosylation of Fcγ receptor III on ligand binding affinity.
Effects of anchor structure and glycosylation of Fcγ receptor III on ligand binding affinity.
复制标题
Fcγ受体III对配体结合亲和力的锚固结构和糖基化的影响。
DOI：
10.1091/mbc.e16-06-0470
复制
发表时间：
2016-11-07
影响因子：
3.3
通讯作者：
Zhu C
中科院分区：
文献类型：
--
作者：
Jiang N;Chen W;Jothikumar P;Patel JM;Shashidharamurthy R;Selvaraj P;Zhu C
CD 16的锚结构以配体特异性方式影响其结合亲和力。当锚从完全变为部分再变为无时，人IgG 1的配体结合亲和力降低，但鼠IgG 2a的配体结合亲和力增加。从CD 16去除N-糖基化也增加配体结合亲和力。Fcγ受体III亚型（FcγRIII或CD 16）是IgG Fc部分的细胞表面受体，也是体液免疫应答的重要调节因子。通过表面等离子体共振在三维和通过微量移液器粘附频率测定在二维中获得FcγRIII同种型的不同配体结合动力学。我们发现，从细胞膜分离的CD 16亚型的锚结构以配体特异性方式影响其结合亲和力。将受体锚结构从完全改变为部分改变为无，降低了对人IgG 1（hIgG 1）的配体结合亲和力，但增加了对鼠IgG 2a（mIgG 2a）的配体结合亲和力。通过衣霉素从CD 16蛋白核心去除N-糖基化也增加配体结合亲和力。分子动力学模拟表明，CD 16的Asn-163处的去糖基化消除了CD 16-hIgG 1 Fc结合的空间位阻，从而增加了结合亲和力。这些结果突出了配体结合受体锚结构和糖基化的意想不到的敏感性，并表明它们各自在变构控制CD 16的配体结合口袋的构象中的作用。
The anchor structure of CD16 affects its binding affinity in a ligand-specific manner. The ligand binding affinity decreases for human IgG1 but increases for murine IgG2a when the anchor is changed from full to partial to none. Removing N-glycosylation from CD16 also increases the ligand binding affinity. Isoforms of the Fcγ receptor III (FcγRIII or CD16) are cell surface receptors for the Fc portion of IgG and important regulators of humoral immune responses. Different ligand binding kinetics of FcγRIII isoforms are obtained in three dimensions by surface plasmon resonance and in two dimensions by a micropipette adhesion frequency assay. We show that the anchor structure of CD16 isoforms isolated from the cell membrane affects their binding affinities in a ligand-specific manner. Changing the receptor anchor structure from full to partial to none decreases the ligand binding affinity for human IgG1 (hIgG1) but increases it for murine IgG2a (mIgG2a). Removing N-glycosylation from the CD16 protein core by tunicamycin also increases the ligand binding affinity. Molecular dynamics simulations indicate that deglycosylation at Asn-163 of CD16 removes the steric hindrance for the CD16-hIgG1 Fc binding and thus increases the binding affinity. These results highlight an unexpected sensitivity of ligand binding to the receptor anchor structure and glycosylation and suggest their respective roles in controlling allosterically the conformation of the ligand binding pocket of CD16.