肝 mTOR 通过调节蛋白激酶 CK2 和 IGFBP-1 磷酸化控制胎儿生长受限的 IGF-I 生物利用度。
Liver mTOR controls IGF-I bioavailability by regulation of protein kinase CK2 and IGFBP-1 phosphorylation in fetal growth restriction.
机构信息
Departments of Pediatrics (M.A.S., M.B.G.) and Biochemistry (I.D., T.S., M.B.G.), Children's Health Research Institute (M.B.G.), University of Western Ontario, London, Ontario N6C 2V5, Canada; Center for Pregnancy and Newborn Research (F.J.R., M.N., P.W.N., T.J.), Department of Obstetrics and Gynecology and Department of Medicine (A.K.), University of Texas Health Science Center San Antonio, Texas 78229; and Geriatric Research Education and Clinical Centers (A.K.), South Texas Veterans Health Care System, San Antonio, Texas 78229.
出版信息
Endocrinology. 2014 Apr;155(4):1327-39. doi: 10.1210/en.2013-1759. Epub 2014 Jan 17.
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.
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。目前尚无针对 FGR 的治疗方法，其潜在的病理生理学仍知之甚少。IGFBP-1 的磷酸化增加已被认为是胎儿生长减少的重要机制。然而，FGR 中循环 IGFBP-1 的磷酸化程度尚不清楚，将 FGR 与 IGFBP-1 磷酸化联系起来的分子机制尚未建立。我们使用了适合胎龄（AGA）和生长受限的人类胎儿的脐带血浆，并通过 ELISA 测定了 IGFBP-1 和 IGF-I 浓度，通过 IGFBP-1 磷酸化位点特异性抗体的 Western 印迹测定了 IGFBP-1 的位点特异性磷酸化。此外，我们使用了通过 30%母体营养限制产生的狨猴 FGR 模型，通过 Western blot、酶测定和 ELISA 测定了狨猴胎肝中的哺乳动物雷帕霉素靶蛋白（mTOR）C1 活性、CK2 表达/活性、IGFBP-1 表达和磷酸化以及 IGF-I 水平。HepG2 细胞和原代狨猴胎肝细胞用于探索 mTORC1 信号与 IGFBP-1 磷酸化之间的机制联系。在人类 FGR 胎儿的脐带血浆中，IGFBP-1 在 Ser101、Ser119 和 Ser169 处发生过度磷酸化。在生长受限的狨猴胎儿的肝脏中，IGFBP-1 也在 Ser101、Ser119 和 Ser169 处过度磷酸化。在体内，生长受限的狨猴胎肝中的 mTOR 信号明显受到抑制，而 CK2 的表达和活性增加。使用 HepG2 细胞和原代狨猴胎肝细胞，我们建立了 mTOR 抑制、CK2 激活、IGFBP-1 过度磷酸化和 IGF-I 诱导的 IGF-I 受体自身磷酸化减少之间的机制联系。我们为 FGR 中的 IGFBP-1 过度磷酸化提供了明确的证据，并确定了 mTOR 和 CK2 介导的调节 IGF-I 生物利用度的机制。我们的研究结果与以下模型一致，即胎儿肝脏中 mTOR 的抑制导致 CK2 活性的增加和 IGFBP-1 的过度磷酸化，这构成了营养剥夺与胎儿生长受限之间的新的机制联系。
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