Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR, USA.
Department of Biomedical Engineering, University of Arkansas, Fayetteville, AR, USA.
Sci Rep. 2017 Jul 13;7(1):5360. doi: 10.1038/s41598-017-05382-1.
Glycosaminoglycans (GAGs), especially heparin and heparan sulfate (HS), modulate the functions of numerous cytokines. The aims of this multidisciplinary research were to characterize heparin binding to interleukin-12 (IL-12) and determine the mechanism(s) by which heparin influences IL-12 bioactivity. Heparin and HS were found to bind human IL-12 (hIL-12) with low micromolar affinity and increase hIL-12 bioactivity by more than 6-fold. Conversely, other GAGs did not demonstrate significant binding, nor did their addition affect hIL-12 bioactivity. Biophysical studies demonstrated that heparin induced only minor conformational changes while size-exclusion chromatography and small angle X-ray scattering studies indicated that heparin induced dimerization of hIL-12. Heparin modestly protected hIL-12 from proteolytic degradation, however, this was not a likely mechanism for increased cytokine activity in vitro. Flow cytometry studies revealed that heparin increased the amount of hIL-12 bound to cell surfaces. Heparin also facilitated hIL-12 binding and signaling in cells in which both hIL-12 receptor subunits were functionally deleted. Results of this study demonstrate a new role for heparin in modulating the biological activity of IL-12.
糖胺聚糖（GAGs），特别是肝素和硫酸乙酰肝素（HS），可调节多种细胞因子的功能。这项多学科研究的目的是研究肝素与白细胞介素-12（IL-12）的结合，并确定肝素影响 IL-12 生物活性的机制。研究发现肝素和 HS 与人类白细胞介素-12（hIL-12）以低微摩尔亲和力结合，并使 hIL-12 生物活性增加超过 6 倍。相反，其他 GAG 则没有明显的结合，也没有影响 hIL-12 生物活性。生物物理研究表明肝素仅诱导轻微的构象变化，而排阻层析和小角 X 射线散射研究表明肝素诱导 hIL-12 的二聚化。肝素适度保护 hIL-12 免受蛋白水解降解，但这不是体外细胞因子活性增加的可能机制。流式细胞术研究表明肝素增加了与细胞表面结合的 hIL-12 量。肝素还促进了细胞中 hIL-12 的结合和信号转导，而细胞中 hIL-12 受体亚基均功能缺失。这项研究的结果表明肝素在调节 IL-12 的生物学活性方面具有新的作用。
