前沿進(jìn)展 | 肝素誘導(dǎo)調(diào)節(jié)人白細(xì)胞介素-12生物活性的分子機(jī)制

人白細(xì)胞介素-12 (hIL-12)是一種可與肝素結(jié)合細(xì)胞因子，前期研究可見其活性可以是由肝素和其他硫酸糖胺聚糖(GAGs)增強(qiáng)。目前的研究探討了肝素增加hIL-12活性的機(jī)制。使用多個人類細(xì)胞類型,包括自然殺傷細(xì)胞,一個IL-12細(xì)胞系,和初級外周血單核細(xì)胞和T細(xì)胞,隨著生物活性,流式細(xì)胞術(shù),和等溫滴定量熱法分析,我們發(fā)現(xiàn)肝素依賴的hIL-12的調(diào)節(jié)功能與肝素的一些生物物理特性,包括鏈長、硫酸鹽化作用水平,和濃度等相關(guān)。具體來說，只有肝素分子長度超過8個糖單位才能增強(qiáng)hIL-12的活性。此外，在hIL-12的結(jié)合和活性增強(qiáng)方面，每個雙糖單元中含有3個硫酸基團(tuán)的肝素分子優(yōu)于每個雙糖單元中含有1或2個硫酸基團(tuán)的肝素分子。肝素還顯著降低hIL-12的EC50達(dá)11.8倍，與不同的細(xì)胞類型相關(guān)。細(xì)胞因子譜分析顯示，肝素影響淋巴細(xì)胞在hIL-12反應(yīng)中產(chǎn)生的細(xì)胞因子的水平，而不是類型。盡管小鼠IL-12也與肝素結(jié)合，但肝素并未增強(qiáng)其活性。利用收集到的數(shù)據(jù)，我們提出了一個hIL-12穩(wěn)定模型，其中肝素作為一種共受體，增強(qiáng)了異二聚體hIL-12及其受體亞基之間的相互作用。本研究結(jié)果為進(jìn)一步研究肝素與IL-12家族細(xì)胞因子的相互作用以及肝素作為免疫調(diào)節(jié)劑的應(yīng)用提供了基礎(chǔ)。

附原文：Human?interleukin-12?(hIL-12) isa heparin-binding cytokine whose activity was previously shown to be enhancedby heparin and other sulfated glycosaminoglycans (GAGs). The current studyinvestigated the?mechanisms?by which heparin increaseshIL-12?activity. Using multiple?humancell types, including naturalkiller cells, an IL-12?indicator cell line, and primary peripheral bloodmononuclear and T cells, along with?bioactivity, flow cytometry, andisothermal titration calorimetry assays, we found that heparin-dependent?modulation?ofhIL-12?function correlates with several of heparin's biophysicalcharacteristics, including chain length, sulfation level, and concentration.Specifically, only heparin molecules longer than eight saccharide units enhancedhIL-12?activity. Furthermore, heparin molecules with three sulfate groupsper disaccharide unit outperformed heparin molecules with one or two sulfategroups per disaccharide unit in terms of enhanced hIL-12?binding andactivity. Heparin also significantly reduced the half-maximal effectiveconcentration of hIL-12?by up to 11.8-fold, depending on the respondingcell type. Cytokine-profiling analyses revealed that heparin affected thelevel, but not the type, of cytokines produced by lymphocytes in response tohIL-12. Interestingly, although murine IL-12?also binds heparin, heparindid not enhance its activity. Using the gathered data, we propose a model ofhIL-12?stabilization in which heparin serves as a co-receptor enhancingthe interaction between heterodimeric hIL-12?and its receptor subunits.The results of this study provide a foundation for further investigation ofheparin's interactions with IL-12?family cytokines and for the use ofheparin as an immunomodulatory agent.

來源：Molecular?mechanisms?of?heparin-induced?modulation?of?human?interleukin?12?bioactivity.

J Biol Chem.?2019 Jan22. pii: jbc.RA118.006193. doi: 10.1074/jbc.RA118.006193. [Epub ahead of print]