Tyrosine phosphorylation of dihydrolipoamide dehydrogenase as a potential cadmium target and its inhibitory role in regulating mouse sperm motility
Tyrosine phosphorylation of dihydrolipoamide dehydrogenase as a potential cadmium target and its inhibitory role in regulating mouse sperm motility
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DOI：
10.1016/j.tox.2016.06.003
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发表时间：
2016-05-16
期刊：
影响因子：
4.5
通讯作者：
Zhang, Yukun
中科院分区：
文献类型：
--
作者：
Li, Xinhong;Wang, Lirui;Zhang, Yukun
据报道，镉 (Cd) 会降低精子活力和功能。然而，镉引起的毒性的分子机制仍然很大程度上未知，这在生殖毒理学研究中存在重大知识空白。在本研究中，我们鉴定了一种候选蛋白二氢硫辛酰胺脱氢酶（DLD），它是一种丙酮酸后代谢酶，在体内和体外暴露于镉的小鼠精子中都表现出酪氨酸磷酸化。免疫沉淀实验表明DLD的酪氨酸残基被磷酸化，Cd处理后表达没有改变，这进一步证实了我们的鉴定结果。然而，DLD的酪氨酸磷酸化并不参与小鼠精子获能，牛血清白蛋白(BSA)有效地阻止了DLD的酪氨酸磷酸化。此外，Cd诱导的DLD酪氨酸磷酸化降低了其脱氢酶活性，同时Cd抑制了烟酰胺腺嘌呤二核苷酸氢（NADH）含量、三磷酸腺苷（ATP）生成和精子活力。有趣的是，当BSA阻断DLD的酪氨酸磷酸化时，DLD活性、NADH和ATP含量以及精子活力的降低也同时受到抑制。这些结果表明，Cd 诱导的 DLD 酪氨酸磷酸化抑制了其活性，从而抑制了三羧酸 (TCA) 循环，从而导致 NADH 减少，从而减少了通过氧化磷酸化 (OPHOXS) 产生的 ATP。综上所述，我们的结果表明，Cd 诱导 DLD 酪氨酸磷酸化，以响应调节 TCA 代谢途径，从而降低 ATP 水平，这些负面影响导致精子活力下降。这项研究为镉对精子活力和功能产生有害影响的机制提供了新的认识。 (C) 2016 Elsevier Ireland Ltd. 保留所有权利。
Cadmium (Cd) is reported to reduce sperm motility and functions. However, the molecular mechanisms of Cd-induced toxicity remain largely unknown, presenting a major knowledge gap in research on reproductive toxicology. In the present study, we identified a candidate protein, dihydrolipoamide dehydrogenase (DLD), which is a post-pyruvate metabolic enzyme, exhibiting tyrosine phosphorylation in mouse sperm exposed to Cd both in vivo and in vitro. Immunoprecipitation assay demonstrated DLD was phosphorylated in tyrosine residues without altered expression after Cd treatment, which further confirmed our identified result. However, the tyrosine phosphorylation of DLD did not participate in mouse sperm capacitation and Bovine Serum Albumin (BSA) effectively prevented the tyrosine phosphorylation of DLD. Moreover, Cd-induced tyrosine phosphorylation of DLD lowered its dehydrogenase activity and meanwhile, Nicotinamide Adenine Dinucleotide Hydrogen (NADH) content, Adenosine Triphosphate (ATP) production and sperm motility were all inhibited by Cd. Interestingly, when the tyrosine phosphorylation of DLD was blocked by BSA, the decrease of DLD activity, NADH and ATP content as well as sperm motility was also suppressed simultaneously. These results suggested that Cd-induced tyrosine phosphorylation of DLD inhibited its activity and thus suppressed the tricarboxylic acid (TCA) cycle, which resulted in the reduction of NADH and hence the ATP production generated through oxidative phosphorylation (OPHOXS). Taken together, our results revealed that Cd induced DLD tyrosine phosphorylation, in response to regulate TCA metabolic pathway, which reduced ATP levels and these negative effects led to decreased sperm motility. This study provided new understanding of the mechanisms contributing to the harmful effects of Cd on the motility and function of spermatozoa. (C) 2016 Elsevier Ireland Ltd. All rights reserved.