Department of Hematology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA.
Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, Virginia, USA.
J Clin Invest. 2018 Nov 1;128(11):5073-5082. doi: 10.1172/JCI99933. Epub 2018 Oct 8.
Arteriolar endothelial cell-expressed (EC-expressed) α-globin binds endothelial NOS (eNOS) and degrades its enzymatic product, NO, via dioxygenation, thereby lessening the vasodilatory effects of NO on nearby vascular smooth muscle. Although this reaction potentially affects vascular physiology, the mechanisms that regulate α-globin expression and dioxygenase activity in ECs are unknown. Without β-globin, α-globin is unstable and cytotoxic, particularly in its oxidized form, which is generated by dioxygenation and recycled via endogenous reductases. We show that the molecular chaperone α-hemoglobin-stabilizing protein (AHSP) promotes arteriolar α-globin expression in vivo and facilitates its reduction by eNOS. In Ahsp-/- mice, EC α-globin was decreased by 70%. Ahsp-/- and Hba1-/- mice exhibited similar evidence of increased vascular NO signaling, including arteriolar dilation, blunted α1-adrenergic vasoconstriction, and reduced blood pressure. Purified α-globin bound eNOS or AHSP, but not both together. In ECs in culture, eNOS or AHSP enhanced α-globin expression posttranscriptionally. However, only AHSP prevented oxidized α-globin precipitation in solution. Finally, eNOS reduced AHSP-bound α-globin approximately 6-fold faster than did the major erythrocyte hemoglobin reductases (cytochrome B5 reductase plus cytochrome B5). Our data support a model whereby redox-sensitive shuttling of EC α-globin between AHSP and eNOS regulates EC NO degradation and vascular tone.
血管内皮细胞表达的（EC 表达的）α-珠蛋白结合内皮型一氧化氮合酶（eNOS），并通过双加氧作用降解其酶产物一氧化氮（NO），从而减弱 NO 对附近血管平滑肌的血管舒张作用。尽管这种反应可能会影响血管生理学，但调节 EC 中α-珠蛋白表达和双加氧酶活性的机制尚不清楚。没有β-珠蛋白，α-珠蛋白不稳定且具有细胞毒性，尤其是在其氧化形式下，这种形式是通过双加氧作用产生的，并通过内源性还原酶循环回收。我们表明，分子伴侣α-血红蛋白稳定蛋白（AHSP）促进体内小动脉α-珠蛋白的表达，并促进其被 eNOS 还原。在 Ahsp-/- 小鼠中，EC α-珠蛋白减少了 70%。Ahsp-/-和 Hba1-/-小鼠表现出相似的血管 NO 信号增加的证据，包括小动脉扩张、α1-肾上腺素能血管收缩减弱和血压降低。纯化的α-珠蛋白结合 eNOS 或 AHSP，但不能同时结合两者。在培养的 EC 中，eNOS 或 AHSP 在后转录水平上增强α-珠蛋白的表达。然而，只有 AHSP 可以防止溶液中氧化的α-珠蛋白沉淀。最后，eNOS 使与 AHSP 结合的α-珠蛋白还原的速度比主要的红细胞血红蛋白还原酶（细胞色素 B5 还原酶加细胞色素 B5）快约 6 倍。我们的数据支持这样一种模型，即 EC α-珠蛋白在 AHSP 和 eNOS 之间的氧化还原敏感穿梭调节 EC 的 NO 降解和血管张力。
