Peroxynitrite-dependent zinc release and inactivation of guanosine 5'-triphosphate cyclohydrolase 1 instigate its ubiquitination in diabetes.
Peroxynitrite-dependent zinc release and inactivation of guanosine 5'-triphosphate cyclohydrolase 1 instigate its ubiquitination in diabetes.
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作者：
Zhao Y;Wu J;Zhu H;Song P;Zou MH
鸟苷 5'-三磷酸环水解酶 1 (GTPCH1) 的异常降解导致四氢生物蝶呤缺乏，被认为是糖尿病内皮功能障碍的主要原因。 GTPCH1 如何变得容易受到降解仍然未知。我们假设过氧亚硝酸盐 (ONOO−)（一氧化氮和超氧阴离子产生的强氧化剂）对锌离子的氧化和释放会引发 GTPCH1 泛素化和降解。在糖尿病小鼠的纯化 GTPCH1、内皮细胞和心脏中检测了锌含量、GTPCH1 泛素化和 GTPCH1 活性。外源性ONOO−剂量依赖性地释放锌，抑制其活性，并增加体外和内皮细胞中GTPCH1的泛素结合亲和力。一致地，高葡萄糖 (30 mmol/L) 会抑制 GTPCH1 活性，同时泛素化增加，而泛素化会受到抗氧化剂的抑制。此外，锌结合半胱氨酸（141）（C141R或C141A）的突变显着降低了GTPCH1活性并缩短了其半衰期，但增加了GTPCH1泛素化，表明锌离子在维持GTPCH1的催化活性和稳定性中发挥着重要作用。最后，在糖尿病小鼠的主动脉和心脏中，GTPCH1 泛素化和降解显着增加，同时 GTPCH1 活性降低，这两种活性在小鼠体内均被 ONOO− 抑制剂减弱。综上所述，我们得出结论，ONOO− 释放锌并抑制 GTPCH1，导致其泛素化和酶降解。
Aberrant degradation of guanosine 5′-triphosphate cyclohydrolase 1 (GTPCH1) with consequent deficiency of tetrahydrobiopterin is considered the primary cause for endothelial dysfunction in diabetes. How GTPCH1 becomes susceptible to the degradation remains unknown. We hypothesized that oxidation and release of the zinc ion by peroxynitrite (ONOO−), a potent oxidant generated by nitric oxide and superoxide anions, instigates GTPCH1 ubiquitination and degradation. Zinc contents, GTPCH1 ubiquitination, and GTPCH1 activity were assayed in purified GTPCH1, endothelial cells, and hearts from diabetic mice. Exogenous ONOO− dose-dependently released zinc, inhibited its activity, and increased the ubiquitin binding affinity of GTPCH1 in vitro and in endothelial cells. Consistently, high glucose (30 mmol/L) inhibited GTPCH1 activity with increased ubiquitination, which was inhibited by antioxidants. Furthermore, mutation of the zinc-binding cysteine (141) (C141R or C141A) significantly reduced GTPCH1 activity and reduced its half-life but increased GTPCH1 ubiquitination, indicating an essential role of the zinc ion in maintaining the catalytic activity and stability of GTPCH1. Finally, GTPCH1 ubiquitination and degradation markedly increased in parallel with decreased GTPCH1 activity in the aortas and hearts of diabetic mice, both of which were attenuated by the inhibitors of ONOO− in mice in vivo. Taken together, we conclude that ONOO− releases zinc and inhibits GTPCH1, resulting in its ubiquitination and degradation of the enzyme.
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影响因子：
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作者：
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DOI：
10.1161/hypertensionaha.110.160622
发表时间：
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