Department of Pathology, University of New Mexico, School of Medicine, Albuquerque, New Mexico.
Department of Pathology, University of New Mexico, School of Medicine, Albuquerque, New Mexico; Department of Physics and Astronomy, University of New Mexico, Albuquerque, New Mexico.
Biophys J. 2023 Sep 19;122(18):3749-3767. doi: 10.1016/j.bpj.2023.07.021. Epub 2023 Jul 27.
Dectin-1A is a C-type lectin innate immunoreceptor that recognizes β-(1,3;1,6)-glucan, a structural component of Candida species cell walls. β-Glucans can adopt solution structures ranging from random coil to insoluble fiber due to tertiary (helical) and quaternary structure. Fungal β-glucans of medium and high molecular weight are highly structured, but low molecular weight glucan is much less structured. Despite similar affinity for Dectin-1, the ability of glucans to induce Dectin-1A-mediated signaling correlates with degree of structure. Glucan denaturation experiments showed that glucan structure determines agonistic potential, but not receptor binding affinity. We explored the impact of glucan structure on molecular aggregation of Dectin-1A. Stimulation with glucan signaling decreased Dectin-1A diffusion coefficient. Fluorescence measurements provided direct evidence of ligation-induced Dectin-1A aggregation, which positively correlated with increasing glucan structure content. In contrast, Dectin-1A is predominantly in a low aggregation state in resting cells. Molecular aggregates formed during interaction with highly structured, agonistic glucans did not exceed relatively small (<15 nm) clusters of a few engaged receptors. Finally, we observed 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.
Dectin-1A 是一种 C 型凝集素先天免疫受体，可识别 β-(1,3;1,6)-葡聚糖，这是真菌细胞壁的结构成分。β-葡聚糖由于三级（螺旋）和四级结构，可以采用从无规卷曲到不溶性纤维的溶液结构。中高分子量的真菌β-葡聚糖高度结构化，但低分子量葡聚糖的结构则少得多。尽管与 Dectin-1A 具有相似的亲和力，但葡聚糖诱导 Dectin-1A 介导的信号转导的能力与结构程度相关。葡聚糖变性实验表明，葡聚糖结构决定了激动剂的潜力，但不决定受体结合亲和力。我们探讨了葡聚糖结构对 Dectin-1A 分子聚集的影响。葡聚糖信号刺激降低了 Dectin-1A 的扩散系数。荧光测量提供了直接证据表明配体诱导的 Dectin-1A 聚集，其与增加的葡聚糖结构含量呈正相关。相比之下，在静止细胞中，Dectin-1A 主要处于低聚集状态。与高度结构化的激动性葡聚糖相互作用时形成的分子聚集体没有超过少数几个参与的受体的相对较小（<15nm）簇。最后，我们观察到 Dectin-1A 在真菌颗粒接触部位的分子聚集增加，其与颗粒表面暴露的葡聚糖程度呈正相关。这些结果表明，Dectin-1A 通过其驱动受体二聚体/寡聚体形成和激活膜近端信号事件的能力的变化来感知β-葡聚糖的溶液构象。
