前沿進展 | 肝素誘導調節人白細胞介素-12生物活性的分子機制

人白細胞介素-12 (hIL-12)是一種可與肝素結合細胞因子，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。目前的研究探討了肝素增加hIL-12活性的機制。使用多個人類細胞類型,包括自然殺傷細胞,一個IL-12細胞系,和初級外周血單核細胞和T細胞,隨著生物活性,流式細胞術,和等溫滴定量熱法分析,我們發現肝素依賴的hIL-12的調節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。具體來說，只有肝素分子長度超過8個糖單位才能增強hIL-12的活性。此外，在hIL-12的結合和活性增強方面，每個雙糖單元中含有3個硫酸基團的肝素分子優于每個雙糖單元中含有1或2個硫酸基團的肝素分子。肝素還顯著降低hIL-12的EC50達11.8倍，與不同的細胞類型相關。細胞因子譜分析顯示，肝素影響淋巴細胞在hIL-12反應中產生的細胞因子的水平，而不是類型。盡管小鼠IL-12也與肝素結合，但肝素并未增強其活性。利用收集到的數據，我們提出了一個hIL-12穩定模型，其中肝素作為一種共受體，增強了異二聚體hIL-12及其受體亞基之間的相互作用。本研究結果為進一步研究肝素與IL-12家族細胞因子的相互作用以及肝素作為免疫調節劑的應用提供了基礎。

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]