Fc γ receptor IIIa/CD16a is an activating cell surface receptor with a well-defined role in natural killer (NK) cell and monocyte effector function. The extracellular domain is decorated with five asparagine (N)-linked glycans; N-glycans at N162 and N45 directly contribute to high-affinity antibody binding and protein stability. N-glycan structures at N162 showed significant donor-dependent variation in a recent study of CD16a isolated from primary human NK cells, but structures at N45 were relatively homogeneous. In this study, we identified variations in N45 glycan structures associated with a polymorphism coding for histidine instead of leucine at position 48 of CD16a from two heterozygous donors. It is known that H48 homozygous individuals suffer from immunodeficiency and recurrent viral infections. A mass spectrometry analysis of protein isolated from the primary natural killer cells of individuals expressing both CD16a L48 and H48 variants demonstrated clear processing differences at N45. CD16a H48 displayed a greater proportion of complex-type N45 glycans compared to the more common L48 allotype with predominantly hybrid N45-glycoforms. Structures at the four other N-glycosylation sites showed minimal differences from data collected on donors expressing only the predominant L48 variant. CD16a H48 purified from a pool of monocytes similarly displayed increased processing at N45. Here, we provide evidence that CD16a processing is affected by the H48 residue in primary NK cells and monocytes from healthy human donors.

中文翻译：

---

来自原代人类自然杀伤细胞和单核细胞的 CD16a N45-聚糖的同种异型特异性加工。

Fc γ 受体 IIIa/CD16a 是一种活化细胞表面受体，在自然杀伤 (NK) 细胞和单核细胞效应器功能中具有明确的作用。胞外域装饰有五个天冬酰胺 (N) 连接的聚糖；N162 和 N45 处的 N-聚糖直接有助于高亲和力抗体结合和蛋白质稳定性。在最近对从原代人类 NK 细胞中分离的 CD16a 的研究中，N162 处的 N-聚糖结构显示出显着的供体依赖性变异，但 N45 处的结构相对均匀。在这项研究中，我们确定了 N45 聚糖结构的变异与编码组氨酸而不是来自两个杂合供体的 CD16a 48 位亮氨酸的多态性相关。众所周知，H48 纯合个体患有免疫缺陷和反复病毒感染。从表达 CD16a L48 和 H48 变体的个体的初级自然杀伤细胞中分离的蛋白质的质谱分析表明，在 N45 处有明显的加工差异。与更常见的 L48 同种异型相比，CD16a H48 显示出更大比例的复合型 N45 聚糖。其他四个 N-糖基化位点的结构与仅表达主要 L48 变体的供体收集的数据差异很小。从单核细胞池中纯化的 CD16a H48 同样显示出在 N45 处的处理增加。在这里，我们提供了 CD16a 加工受原代 NK 细胞和健康人类供体单核细胞中 H48 残基影响的证据。