Regulation and Biosynthesis of Ecdysteroid Hormones

甲壳动物的生长、蜕皮和再生是由体腔中一对腺体(Y器官)中的类固醇激素(蜕皮激素)控制的。Y器官反过来又受大脑的蛋白质荷尔蒙(MIH)调节。这个系统类似于人类的腺体(睾丸、卵巢、肾上腺)，分泌类固醇激素(睾酮、雌激素、皮质醇)，由脑下垂体和大脑的蛋白质荷尔蒙控制。我们发现，甲壳类动物和人类一样，会从胆固醇中产生类固醇激素。因此，我们使用甲壳动物的腺体作为简化模型来研究胆固醇如何进入细胞并转化为激素，以及这一过程如何受到外部蛋白质的调节。我们已经知道甲壳类血液中的所有胆固醇都与高密度脂蛋白(HDL)结合，Y器官表面有识别和结合高密度脂蛋白的受体。使用放射性标记的胆固醇和高密度脂蛋白、电子显微镜和超速离心机，我们现在将发现胆固醇是如何进入细胞的，如果它仍然与高密度脂蛋白结合，它是如何被加工的，以及加工在细胞中的什么地方发生。这项研究的一部分是确定MIH如何控制胆固醇进入；例如，MIH是否改变了高密度脂蛋白的受体数量？我们还将尝试通过使用质谱仪来识别胆固醇转化为激素的各个步骤，从而确定蜕皮类固醇生物合成的细节。这个项目涵盖了神经生物学、内分泌学和发展领域，解决了神经内分泌功能协调的基本问题。

Growth, molting and regeneration in crustaceans is controlled by steroid hormones (ecdysteroids) from a pair of glands (Y-organs) in the body cavity. The Y-organs in turn are regulated by a protein hormone (MIH) from the brain. This system is comparable to human glands (testis, ovary, adrenal) that secrete steroid hormones (testosterone, estrogen, cortisone) and are controlled by protein hormones from pituitary and brain. We have found that crustaceans, like humans, make steroid hormones from cholesterol. Accordingly, we use crustacean glands as a simplified model to study how cholesterol enters cells and is converted to hormones, and how the process is regulated by the external proteins. We already know that all cholesterol in crustacean blood is bound to high-density lipoprotein (HDL), and that there are receptors on the surface of Y-organ that recognize and bind the HDL. Using radioactively labeled cholesterol and HDL, the electron microscope and the ultracentrifuge, we now will find how cholesterol enters the cells, how it is processed if still bound to HDL and where in the cells the processing takes place. Part of the study is to determine how MIH controls cholesterol entry; e.g., does MIH change the number of receptors for HDL? We will also attempt to work out the details of the biosynthesis of ecdysteroids, by using the mass spectrograph to identify the individual steps in the conversion of cholesterol to the hormones. This project embraces the fields of neurobiology, endocrinology and development in addressing basic questions on neuroendocrine coordination of functions.