昆虫抑咽侧体神经肽功能及作用机制

回顾了近年来研究较多的昆虫咽侧体神经肽(AS)功能及作用机制方面的新进展。相关研究认为,大多数AS抑制CA对JH的合成。在JH的合成途径中,AS的抑制作用发生在JH生物合成的第一步,cAMP可能是其第二信使。但有些A型的AS对源昆虫的CA没有作用,这可能是在这些昆虫中存在另一个抑制JH合成的机制,包括完全不同类型的AS及第二信使等。一种昆虫中多个A型的AS成员基本上来自一个单一的多肽前体,这些成员可能作用于不同亚类的受体。A型的AS可能通过抑制对卵黄蛋白原的合成或吸收来抑制直翅类昆虫卵巢的发育,这个作用也可能与抑制CA对JH的合成有关。AS能抑制前肠、中肠、后肠肌肉的收缩,导致昆虫厌食、生长延迟、死亡率上升等现象,此外,还能抑制心脏、背血管和输卵管等器官中肌肉的收缩。AS对肌肉收缩的抑制的作用可能由一个Gi蛋白受体介导,且这类受体与AS抑制CA活性时的受体可能完全不同。

Functions and Mechenism of Insect Allatostatins

Recent advances in functions and mechanisms of insect allatostatins are reviewed. Relevant researches showed that most insect allatostatins inhibit the biosynthesis of JH by corpora allata (CA), which may function at the first step of biosynthesis pathway of JH and cAMP maybe is its second messenger. While some allatostatins of type A have no effect on CA of source insects, for there may be another mechenism of inhibiting JH synthesis in these insects, including different allatostatins and second messengers. Several allatostatins of type A from the same insect are origined from a single proprecursor, which maybe function via a complex mix with different affinity interactions with receptors in the CA. Allatostains of type A maybe inhibit vitellogenesis in orthopteroid insects through inhibition of biosynthesis and/or uptake of vitelloginin, and this function maybe relates to the inhibition of biosynthesis of JH by CA. Allatostatins have myoinhabitory effects on foregut, midgut and hindgut, which result in inhibition of food taking and growth as well as higher rate of mortality. Furthermore, allatostatins inhibit contraction of muscles in heart, dorsal vessel and oviducts. The myoinhabitory role of allatostatins may be mediated by a Gi-protein, which may be different from the receptor coupling with AS to inhibit the activity of CA.