Liver mTOR Controls IGF-I Bioavailability by Regulation of Protein Kinase CK2 and IGFBP-1 Phosphorylation in Fetal Growth Restriction
Liver mTOR Controls IGF-I Bioavailability by Regulation of Protein Kinase CK2 and IGFBP-1 Phosphorylation in Fetal Growth Restriction
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DOI：
10.1210/en.2013-1759
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发表时间：
2014-04-01
期刊：
影响因子：
4.8
通讯作者：
Gupta, Madhulika B.
中科院分区：
文献类型：
--
作者：
Abu Shehab, Majida;Damerill, Ian;Gupta, Madhulika B.
胎儿生长受限（FGR）增加了围产期并发症的风险，并使婴儿在以后的生活中易患糖尿病和心血管疾病。目前尚无FGR的治疗方法，其潜在的病理生理机制仍知之甚少。IGFBP-1磷酸化的增加被认为是胎儿生长减少的重要机制。然而，循环IGFBP-1在FGR中磷酸化的程度是未知的，并且将FGR与IGFBP-1磷酸化联系起来的分子机制尚未建立。我们使用适合胎龄（阿加）和生长受限的人胎儿的脐带血浆，并测定IGFBP-1和IGF-I浓度（ELISA）和位点特异性IGFBP-1磷酸化（使用IGFBP-1磷酸化位点特异性抗体的蛋白质印迹法）。此外，我们使用由30%母体营养限制产生的FGR狒狒模型，并通过Western印迹、酶法测定和ELISA测定狒狒胎肝中的哺乳动物雷帕霉素靶蛋白（mTOR）C1活性、CK 2表达/活性、IGFBP-1表达和磷酸化以及IGF-I水平。HepG 2细胞和原代胎狒狒肝细胞用于探索mTORC 1信号传导和IGFBP-1磷酸化之间的机制联系。IGFBP-1在人FGR胎儿脐带血浆中的Ser 101、Ser 119和Ser 169高度磷酸化。IGFBP-1在生长受限狒狒胎儿肝脏中的Ser 101、Ser 119和Ser 169处也高度磷酸化。在体内生长受限的狒狒胎肝中，mTOR信号被显著抑制，而CK 2的表达和活性增加。使用HepG 2细胞和原代胎狒狒肝细胞，我们建立了mTOR抑制、CK 2激活、IGFBP-1过度磷酸化和IGF-I诱导的IGF-I受体自身磷酸化降低之间的机制联系。我们提供了FGR中IGFBP-1过度磷酸化的明确证据，并确定了mTOR和CK 2介导的IGF-I生物利用度调节机制。我们的研究结果与模型一致，即胎肝中mTOR的抑制，导致CK 2活性增加和IGFBP-1过度磷酸化，构成了营养缺乏和胎儿生长受限之间的新机制联系。
Fetal growth restriction (FGR) increases the risk for perinatal complications and predisposes the infant to diabetes and cardiovascular disease later in life. No treatment for FGR is available, and the underlying pathophysiology remains poorly understood. Increased IGFBP-1 phosphorylation has been implicated as an important mechanism by which fetal growth is reduced. However, to what extent circulating IGFBP-1 is phosphorylated in FGR is unknown, and the molecular mechanisms linking FGR to IGFBP-1 phosphorylation have not been established. We used umbilical cord plasma of appropriate for gestational age (AGA) and growth-restricted human fetuses and determined IGFBP-1 and IGF-I concentrations (ELISA) and site-specific IGFBP-1 phosphorylation (Western blotting using IGFBP-1 phospho-site specific antibodies). In addition, we used a baboon model of FGR produced by 30% maternal nutrient restriction and determined mammalian target of rapamycin (mTOR) C1 activity, CK2 expression/activity, IGFBP-1 expression and phosphorylation, and IGF-I levels in baboon fetal liver by Western blot, enzymatic assay, and ELISA. HepG2 cells and primary fetal baboon hepatocytes were used to explore mechanistic links between mTORC1 signaling and IGFBP-1 phosphorylation. IGFBP-1 was hyperphosphorylated at Ser101, Ser119, and Ser169 in umbilical plasma of human FGR fetuses. IGFBP-1 was also hyperphosphorylated at Ser101, Ser119, and Ser169 in the liver of growth-restricted baboon fetus. mTOR signaling was markedly inhibited, whereas expression and activity of CK2 was increased in growth-restricted baboon fetal liver in vivo. Using HepG2 cells and primary fetal baboon hepatocytes, we established a mechanistic link between mTOR inhibition, CK2 activation, IGFBP-1 hyperphosphorylation, and decreased IGF-I-induced IGF-I receptor autophosphorylation. We provide clear evidence for IGFBP-1 hyperphosphorylation in FGR and identified an mTOR and CK2-mediated mechanism for regulation of IGF-I bioavailability. Our findings are consistent with the model that inhibition of mTOR in the fetal liver, resulting in increased CK2 activity and IGFBP-1 hyperphosphorylation, constitutes a novel mechanistic link between nutrient deprivation and restricted fetal growth.