The function and regulation of the novel pregnancy-specific hexokinase HKDC1

 描述（由申请人提供）：孕激素高血糖可导致母亲和后代的急性和慢性不良结局。在最近的一项高血压和不良妊娠结局（HAPO）队列的遗传研究中，PI Layden、共同研究者Reddy和共同作者报告了一个与妊娠期母体血糖性状相关的新基因座。相关区域中的前导候选基因编码含己糖激酶结构域1（HKDC 1）蛋白。因此，本研究的总体目标是了解新基因HKDC1在妊娠期葡萄糖稳态中的作用。最近，PI Layden和共同研究者Reddy发表了HKDC 1的第一个表征，出乎意料地揭示了HKDC 1是第五种脊椎动物己糖激酶（Guo et al.，2015 Nature Communications）。该提案的目标是建立在这些初步发现的基础上，以验证HKDC 1是一种控制妊娠期间葡萄糖稳态的新型己糖激酶的中心假设。验证这一假设很重要，因为它将揭示导致全球最常见的妊娠并发症之一的新机制。这些结果也将对理解脊椎动物代谢产生广泛的影响，因为己糖激酶是糖酵解的第一步，第五种人类己糖激酶的首次表征将大大改变我们对健康和疾病期间控制葡萄糖稳态的酶的基本理解。中心假设将在三个互补层面上进行检验。首先，在初步发现HKDC 1是一种己糖激酶之后，将系统地表征该蛋白的酶活性。这样做将揭示HKDC 1是否更可能负责葡萄糖传感或葡萄糖代谢，并将HKDC 1与其他己糖激酶联系起来。这些见解对于理解HKDC1在孕产妇健康方面的作用至关重要。其次，将评估HKDC 1在妊娠期间葡萄糖稳态中的体内作用。组织表达模式表明，HKDC1在妊娠期间特别通过其在胰腺β细胞和肝脏中的作用调节葡萄糖稳态。通过整体和组织特异性消融小鼠模型，将评估妊娠期间的葡萄糖稳态。这些发现将转化为人胰岛和原代人肝细胞的体外研究。第三，HKDC1在人类妊娠期间调节葡萄糖的作用将通过检验妊娠期高血糖症相关的遗传变异改变HKDC1在妊娠期间的调节这一假设来研究。该假设将使用新型高通量报告基因测定法进行测试，以（i）发现调节HKDC 1表达的初级和次级激素和葡萄糖反应元件，以及（ii）鉴定改变原始GWAS群体中调节元件功能的遗传变体。这项建议的结果将是全面了解怀孕期间HKDC1的活性和转录调控。从长远来看，这些发现将支持下游预测，预防和治疗妊娠高血糖症的努力。

 DESCRIPTION (provided by applicant): Gestational hyperglycemia can result in acute and chronic adverse outcomes for mother and offspring. In a recent genetic study of the Hyperglycemia and Adverse Pregnancy Outcomes (HAPO) cohort, PI Layden, Co- investigator Reddy, and co-authors reported a novel loci associated with maternal glycemic traits specifically during pregnancy. The lead candidate gene in the associated region encodes the hexokinase-domain containing 1 (HKDC1) protein. Therefore, the overall objective of this proposal is to understand the role of the novel gene HKDC1 in gestational glucose homeostasis. Recently, PI Layden and co-Investigator Reddy published the first characterization of HKDC1, revealing unexpectedly that HKDC1 is a fifth vertebrate hexokinase (Guo et al., 2015 Nature Communications). The goal of this proposal, which builds upon those initial findings, is to test the central hypothesis that HKDC1 is a novel hexokinase that controls glucose homeostasis during pregnancy. Testing that hypothesis is important because it will reveal new mechanisms contributing to one of the most common complications of pregnancy worldwide. The results will also have broad-reaching impacts on understanding vertebrate metabolism because hexokinase is the first step in glycolysis, and the first characterization of the fifth human hexokinase will substantially revise our basic understanding of the enzymes controlling glucose homeostasis during health and disease. The central hypothesis will be tested at three complementary levels. First, following up on the initial discovery that HKDC1 is a hexokinase, the enzymatic activity of the protein will be systematically characterized. Doing so will reveal whether HKDC1 is more likely responsible for glucose sensing or glucose metabolism, and will relate HKDC1 to the other hexokinases. Those insights are essential for understanding the role of HKDC1 in maternal health. Second, the in vivo role of HKDC1 in glucose homeostasis during pregnancy will be assessed. Tissue expression patterns suggest that HKDC1 regulates glucose homeostasis during pregnancy specifically through its role in pancreatic β cells and liver. Through global and tissue-specific ablation mouse models, glucose homeostasis during pregnancy will be assessed. These findings will be translated to in vitro studies in human islets and primary human hepatocytes. Third, the role of HKDC1 in regulating glucose during human pregnancy will be investigated by testing the hypothesis that gestational hyperglycemia-associated genetic variants alter the regulation of HKDC1 during pregnancy. That hypothesis will be tested using novel high- throughput reporter assays (i) to discover the primary and secondary hormone and glucose response elements that regulate HKDC1 expression and (ii) to identify genetic variants that alter regulatory element function in the original GWAS population. The outcome of this proposal will be a comprehensive understanding of the activity and transcriptional regulation of HKDC1 during pregnancy. Long term, those findings will support downstream efforts to predict, prevent, and treat gestational hyperglycemia.