PROCESSING OF HCG IN NORMAL AND ABNORMAL PREGNANCIES

我们实验室的初步研究与高糖基化(N-连接的寡糖上增加的触角和岩藻糖残基)与hCG的划痕或裂解之间的关系是一致的。其他初步研究表明，高糖化的hCG分子和含镍的hCG分子的结构不稳定和生物活性降低，以及它们如何可能成为循环中游离的β亚基和尿样中的β核心片段的来源。已发表的论文显示，滋养细胞疾病、妊娠剧吐或唐氏综合征患者的血清或尿样中hCG水平升高，游离β亚基和β核心片段水平的比例增加。我们的假设是，这些升高的水平是由hCG的高糖基化引起的，通过涉及划痕的途径，无效的自分泌控制hCG的产生，解离到镍的游离的β-亚基，并降解为β-核心片段。其他途径可提高先兆子痫患者的hCG水平，降低高糖化hCG的比例。提出了四组实验来验证这一假设，并调查了观察到的正常和异常妊娠的临床分支。本研究拟对1140组正常妊娠和异常妊娠的平行血清和尿样中hCG、游离β-亚基和β-核心片段的水平进行确认和比较(目标1A)；并使用平行的血清和尿样来研究两种新的免疫分析方法的临床应用，以及它们在唐氏综合征和先兆子痫筛查中的潜在应用(目标1B)。拟进行基础科学研究，从正常妊娠早、中、晚期妊娠尿样以及先兆子痫、恶性滋养细胞疾病和唐氏综合征孕妇尿样(各3例)中提纯hCG，并比较划痕的程度和位置，以及高糖化N-连接寡糖的类型、数量和位置(目标2)。进一步的研究计划通过比较正常和高糖基化的hCG作为切割酶的底物来研究高糖基化-切割的关系(目标3)；并检测21个纯化的正常和异常妊娠分子的生物学活性，并确定它们通过胎盘反馈和控制hCG合成的能力(目标4)。

Preliminary studies in our laboratory are consistent with a relationship between hyperglycosylation (additional antennae and fucose residues on N-linked oligosaccharides) and nicking or cleavage of hCG. Other preliminary studies indicate the structural instability and diminished biological activity of hyperglycosylated and of nicked hCG molecules, and how they may be the source of free beta-subunit in the circulation and beta-core fragment in urine samples. Papers have been published showing raised hCG levels, and raised proportions of free beta-subunit and beta-core fragment levels in serum or urine samples from patients with trophoblast disease, hyperemesis gravidarum, or Down syndrome pregnancies. It is our hypothesis these raised levels arise from the hyperglycosylation of hCG, through pathways involving nicking, ineffectual autocrine control of hCG production, and dissociation to nicked free beta-subunit, and degradation to beta-core fragment. Other pathways raise levels of hCG and lower the proportions of hyperglycosylated hCG in patients with preeclampsia. Four sets of experiments are proposed to test this hypothesis and investigate the clinical ramification of the observations in normal and abnormal pregnancies. Studies are proposed to confirm and compare the levels of hCG, free beta-subunit and beta-core fragment in 1140 sets of parallel serum and urine samples from normal and abnormal pregnancies (Aim 1A); and to use the parallel serum and urine samples to investigate the clinical use of two new immunoassays that specifically measure hyperglycosylated hCG and nicked hCG, and their potential uses in screening for Down syndrome and preeclampsia (Aim 1B). Basic science studies are proposed to purify hCG from normal first, second and third trimester pregnancy urine samples, and preeclampsia, hyperemesis trophoblast disease and Down syndrome pregnancy urine samples (3 each) and compare the extents and sites of nicking, and the type, amounts and locations of hyperglycosylated N-linked oligosaccharides (Aim 2). Further studies are planned to investigate the hyperglycosylation- nicking relationship by comparing normal and hyperglycosylated hCG as substrates for nicking enzymes (Aim 3); and to examine the biological activities of the 21 purified normal and abnormal pregnancy molecules, and to determine their ability abilities to feedback through to the placenta and control hCG synthesis (Aim 4).