前沿进展 | 肝素诱导调节人白细胞介素-12生物活性的分子机制

人白细胞介素-12 (hIL-12)是一种可与肝素结合细胞因子，前期研究可见其活性可以是由肝素和其他硫酸糖胺聚糖(GAGs)增强。目前的研究探讨了肝素增加hIL-12活性的机制。使用多个人类细胞类型,包括自然杀伤细胞,一个IL-12细胞系,和初级外周血单核细胞和T细胞,随着生物活性,流式细胞术,和等温滴定量热法分析,我们发现肝素依赖的hIL-12的调节功能与肝素的一些生物物理特性,包括链长、硫酸盐化作用水平,和浓度等相关。具体来说，只有肝素分子长度超过8个糖单位才能增强hIL-12的活性。此外，在hIL-12的结合和活性增强方面，每个双糖单元中含有3个硫酸基团的肝素分子优于每个双糖单元中含有1或2个硫酸基团的肝素分子。肝素还显著降低hIL-12的EC50达11.8倍，与不同的细胞类型相关。细胞因子谱分析显示，肝素影响淋巴细胞在hIL-12反应中产生的细胞因子的水平，而不是类型。尽管小鼠IL-12也与肝素结合，但肝素并未增强其活性。利用收集到的数据，我们提出了一个hIL-12稳定模型，其中肝素作为一种共受体，增强了异二聚体hIL-12及其受体亚基之间的相互作用。本研究结果为进一步研究肝素与IL-12家族细胞因子的相互作用以及肝素作为免疫调节剂的应用提供了基础。

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.

来源：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]