Corticosteroid‐binding globulin (CBG) transports cortisol and other steroids. High‐affinity CBG (haCBG) undergoes proteolysis of the reactive center loop (RCL) by neutrophil elastase (NE) altering conformation to low‐affinity CBG (laCBG). Elevated temperature reduces CBG:cortisol binding affinity. Surface plasmon resonance was used to determine binding profiles of 19 steroids to haCBG and laCBG at 25, 37, and 39°C mimicking pyrexia and pH 7.4 and 7.0 mimicking acidosis, pathophysiological conditions relevant to sepsis. An expected 4–8‐fold reduction in affinity for cortisol, cortisone, corticosterone, 11‐deoxycortisol, progesterone, 17‐hydroxyprogesterone, and prednisolone occurred with NE‐mediated haCBG‐to‐laCBG conversion. CBG:cortisol binding affinity was further reduced 3.5‐fold at 39°C relative to 37°C, binding affinity was also reduced by acidosis for both haCBG and laCBG. Using a conformational antibody generated against the RCL, we confirmed RCL antibody binding was eliminated by NE cleavage, but preserved in pyrexia and acidosis. Molecular modeling studies performed at 40°C confirmed a critical role for Trp371, positioned within the steroid‐binding pocket, in ligand binding. These studies demonstrated CBG binding affinity to range of steroids is ligand specific and is reduced with NE‐mediated haCBG‐to‐laCBG transition. Reduced CBG:cortisol binding occurs with increased temperature and in acidosis. Increased flexibility of the Trp371 side chain is proposed in the thermo‐coupling mechanism of cortisol release. The synergy of NE cleavage, pyrexia, and acidosis on CBG:cortisol binding may serve to enhance cortisol delivery to the interstitial space in inflammation.

中文翻译：

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发热和酸中毒独立于中性粒细胞弹性蛋白酶反应中心环裂解作用，影响皮质醇从皮质类固醇结合球蛋白中释放

皮质类固醇结合球蛋白 (CBG) 运输皮质醇和其他类固醇。高亲和力 CBG (haCBG) 通过中性粒细胞弹性蛋白酶 (NE) 将反应中心环 (RCL) 蛋白水解成低亲和力 CBG (laCBG) 的构象。升高的温度会降低 CBG：皮质醇的结合亲和力。表面等离子共振用于确定 25、37 和 39°C 下 19 种类固醇与 haCBG 和 laCBG 的结合谱，模拟发热，pH 7.4 和 7.0 模拟酸中毒，与败血症相关的病理生理条件。在 NE 介导的 haCBG 到 laCBG 的转化中，对皮质醇、可的松、皮质酮、11-脱氧皮质醇、孕酮、17-羟基孕酮和泼尼松龙的亲和力预期降低 4-8 倍。CBG：皮质醇结合亲和力在 39°C 下比 37°C 进一步降低了 3.5 倍，haCBG 和 laCBG 的酸中毒也降低了结合亲和力。使用针对 RCL 产生的构象抗体，我们确认 RCL 抗体结合被 NE 切割消除，但在发热和酸中毒中保留。在 40°C 下进行的分子建模研究证实了位于类固醇结合口袋内的 Trp371 在配体结合中的关键作用。这些研究表明，CBG 对一系列类固醇的结合亲和力是配体特异性的，并且随着 NE 介导的 haCBG 到 laCBG 的转变而降低。降低 CBG：皮质醇结合会随着温度升高和酸中毒而发生。在皮质醇释放的热耦合机制中提出了增加 Trp371 侧链的灵活性。NE 裂解、发热和酸中毒对 CBG 的协同作用：