Quayle Kenneth, Coy Catherine, Standish Leanna, Lu Hailing
Tumor Vaccine Group, Department of Medicine, University of Washington, 850 Republican Street, Seattle, WA, 98109, USA,
J Nat Med. 2015 Apr;69(2):198-208. doi: 10.1007/s11418-014-0879-z. Epub 2014 Dec 16.
Protein-bound polysaccharide-K (Krestin; PSK) is a hot-water extract of Trametes versicolor with immune stimulatory activity. It has been used for the past 30 years and has demonstrated anti-tumor efficacy in multiple types of cancer. The ability of PSK to activate dendritic cells and T cells is dependent on its ability to stimulate Toll-like receptor 2 (TLR2), yet it remains unknown which structural component within PSK activates TLR2. The purpose of this study was to identify the TLR2 agonist within PSK and understand its role in the overall mechanism of PSK's immunogenic activity. TLR2 activity was eliminated by treatment with lipoprotein lipase but not by trypsin or lyticase. Rapid centrifugation of PSK can separate the fraction with TLR2 agonist activity from the soluble β-glucan fraction. To study the potential interaction between the β-glucan component and the lipid component, we labeled the soluble β-glucan with fluorescein. Uptake of the labeled β-glucan by J774A macrophages and JAWSII dendritic cells was inhibited by anti-Dectin-1 antibody but not by anti-TLR2 antibody, confirming that Dectin-1 is the receptor for β-glucan. Interestingly, pre-treatment of JAWSII cells with the TLR2-active lipid fraction significantly enhanced the uptake of the soluble β-glucan, indicating the synergy between the TLR2 agonist component and the β-glucan component. Altogether, these results present evidence that PSK has two active components-the well-characterized protein-bound β-glucan and a previously unreported lipid-which work synergistically via the Dectin-1 and TLR2 receptors.
蛋白结合多糖K（云芝多糖K；PSK）是云芝的热水提取物，具有免疫刺激活性。在过去30年中它一直被使用，并已在多种癌症中显示出抗肿瘤疗效。PSK激活树突状细胞和T细胞的能力取决于其刺激Toll样受体2（TLR2）的能力，但PSK中哪种结构成分激活TLR2仍不清楚。本研究的目的是鉴定PSK中的TLR2激动剂，并了解其在PSK免疫原性活性整体机制中的作用。用脂蛋白脂肪酶处理可消除TLR2活性，但用胰蛋白酶或溶菌酶处理则不能。对PSK进行快速离心可将具有TLR2激动剂活性的部分与可溶性β-葡聚糖部分分离。为了研究β-葡聚糖成分与脂质成分之间的潜在相互作用，我们用荧光素标记了可溶性β-葡聚糖。抗Dectin-1抗体可抑制J774A巨噬细胞和JAWSII树突状细胞对标记的β-葡聚糖的摄取，而抗TLR2抗体则不能，这证实了Dectin-1是β-葡聚糖的受体。有趣的是，用具有TLR2活性的脂质部分预处理JAWSII细胞可显著增强可溶性β-葡聚糖的摄取，表明TLR2激动剂成分与β-葡聚糖成分之间存在协同作用。总之，这些结果表明PSK有两种活性成分——特征明确的蛋白结合β-葡聚糖和一种以前未报道的脂质——它们通过Dectin-1和TLR2受体协同发挥作用。
