Molecular physiological studies on insect excretion and water regulation and its application -physiology of aquaporin and its disorder-

50多年来，人们一直在探索水运输中的上皮和细胞机制。近年来，关于生物体内水分调节的分子方面的知识有了很大的增长。水通过质膜的运输依赖于水通道-水通道蛋白(AQP)的存在。尽管离子和水的运动有着千丝万缕的联系，但到目前为止，关于昆虫上皮中水分运输本身的研究还很缺乏。目前，有关AQP在昆虫上皮细胞中的多种功能的生理学研究还很少。本课题旨在研究昆虫水通道蛋白的研究现状以及毛虫水通道蛋白的分子和细胞功能的最新研究进展。目前，除毛虫的水通道蛋白外，所有昆虫水通道蛋白都是水特异性的，它具有另一种能够运输甘油和尿素的异构体(水甘油通道蛋白：GLP)。昆虫中与水有关的水通道蛋白被分为两个亲缘关系密切的亚家族，在系统发育上称为果蝇固有蛋白(Drodexila Intrative Protein)和果蝇固有蛋白(Pyrocoelia Rufa Intrative Protein)。在最近的报告中，昆虫AQP属于水滴或PRIP。在家蚕中，我们已经鉴定出这三种类型，即AQP-Bom1为滴流型，Bom2为GLP-型，Bom3为PRIP-型。毛虫(固体/植物喂食者)与液体/植物喂食者(如叶蝉)相比，通常能耐受干旱和饥饿。因此，家蚕幼虫的这三种水通道蛋白协同作用，不仅维持了家蚕幼虫体内的水分平衡，而且还维持了家蚕幼虫的排泄。

Epithelial and cellular mechanisms in water transport has been explored over 50 years. Knowledge on the molecular aspects of water regulation in living organisms has greately increased in recent years. Water transport across the plasma membrane depends on the presence of water channel-aquaporin (AQP). Studies on water transport itself in insect epithelia is so far lacking, although the movement of ions and water are inextricably linked. There are still few physiological studies on the multiple functions of AQP in insect epithelia. This project set out to investigate the present status on our understanding of insect aquaporins and the recent advances in the molecular and cellular roles of caterpillar's AQP.Currently, all insect AQPs are water-specific except for the caterpillar's AQP, which possess the other isoform which enables to transport glycerol and urea (aquaglyceroporin : GLP). Water-specific AQPs in insects are classified into two closely related subfamilies, called DRIP (Drosophila Intrinsic Protein) and PRIP (Pyrocoelia rufa Intrinsic Protein) phylogenetically. Insect AQPs in very recent reports fall into DRIP or PRIP. In the silkworm, Bombyx mori, we have identified these three types, i.e., AQP-Bom1 as DRIP-type, Bom2 as GLP-type, Bom3 as PRIP-type. Caterpillars (solid/plant feeder) are normally endurable against drought and starvation compare to the liquid/plant feeders such as a leafhopper. Therefore, these three AQPs of B. mori, collaborate to maintain not only water balance, but also excretion in silkworm larvae.