Dectin-1A is a C-type Lectin innate immunoreceptor that recognizes β-(1,3:1,6)-glucan, a structural component of Candidaspecies cell walls. The higher order structure of β-glucans ranges from random coil to insoluble fiber due to varying degrees of tertiary (helical) and quaternary structure. Model Saccharomyces cerevisiaeβ-glucans of medium and high molecular weight (MMW and HMW, respectively) are highly structured. In contrast, low MW glucan (LMW) is much less structured. Despite similar affinity for Dectin-1A, the ability of glucans to induce Dectin-1A mediated calcium influx and Syk phosphorylation positively correlates with their degree of higher order structure. Chemical denaturation and renaturation of MMW glucan showed that glucan structure determines agonistic potential, but not binding affinity, for Dectin-1A. We explored the role of glucan structure on Dectin-1A oligomerization, which is thought to be required for Dectin-1 signaling. Glucan signaling decreased Dectin-1A diffusion coefficient in inverse proportion to glucan structural content, which was consistent with Dectin-1A aggregation. Förster Resonance Energy Transfer (FRET) measurements revealed that molecular aggregation of Dectin-1 occurs in a manner dependent upon glucan higher order structure. Number and Brightness analysis specifically confirmed an increase in the Dectin-1A dimer and oligomer populations that is correlated with glucan structure content. Receptor modeling data confirms that in resting cells, Dectin-1A is predominantly in a monomeric state. Super Resolution Microscopy revealed that glucan-stimulated Dectin-1 aggregates are very small (<15 nm) collections of engaged receptors. Finally, FRET measurements confirmed increased molecular aggregation of Dectin-1A at fungal particle contact sites in a manner that positively correlated with the degree of exposed glucan on the particle surface. These results indicate that Dectin-1A senses the solution conformation of β-glucans through their varying ability to drive receptor dimer/oligomer formation and activation of membrane proximal signaling events.

中文翻译：

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Dectin-1分子聚集和信号传导对白色念珠菌细胞壁上的β-葡聚糖结构和葡聚糖暴露敏感。

Dectin-1A是一种C型凝集素固有免疫受体，可识别β-（1,3：1,6）-葡聚糖（念珠菌属细胞壁的结构成分）。由于三级（螺旋）和四级结构的程度不同，β-葡聚糖的高级结构范围从无规卷曲到不溶性纤维。中等和高分子量的酿酒酵母β-葡聚糖模型（分别为MMW和HMW）具有高度结构化。相反，低分子量葡聚糖（LMW）的结构要少得多。尽管对Dectin-1A的亲和力相似，但葡聚糖诱导Dectin-1A介导的钙内流和Syk磷酸化的能力与它们的高阶结构程度正相关。MMW葡聚糖的化学变性和复性表明，葡聚糖结构决定了Dectin-1A的激动潜能，但不决定其结合亲和力。我们探讨了葡聚糖结构对Dectin-1A寡聚的作用，据认为这是Dectin-1信号转导所必需的。葡聚糖信号以与葡聚糖结构含量成反比的方式降低Dectin-1A扩散系数，这与Dectin-1A聚集相一致。Förster共振能量转移（FRET）测量表明，Dectin-1的分子聚集以依赖于葡聚糖更高阶结构的方式发生。数量和亮度分析特别证实了Dectin-1A二聚体和低聚物群体的增加，这与葡聚糖结构含量有关。受体模型数据证实，在静息细胞中，Dectin-1A主要处于单体状态。超分辨率显微镜显示，葡聚糖刺激的Dectin-1聚集体非常小（< 15 nm）的受体集合。最后，FRET测量证实，真菌颗粒接触位点的Dectin-1A分子聚集增加，其与颗粒表面暴露的葡聚糖的程度呈正相关。这些结果表明，Dectin-1A通过其驱动受体二聚体/低聚物形成和激活膜近端信号事件的变化能力来感知β-葡聚糖的溶液构象。