昆虫体内的酪胺:合成、降解与生理功能

Tyramine in insects: synthesis, degradation and physiological functions

作为神经活性物质,昆虫体内的酪胺(tyramine, TA)主要在酪胺能神经元中合成,但也可在马氏管主细胞中合成。TA在结合其受体发挥生理功能后,可被突触前膜的转运体(transporter)转运回突触前膜重复利用。N-酰基化可能是昆虫体内TA降解的主要途径。目前,昆虫体内发现的TA受体均属于G蛋白偶联受体,通过与Gi或Gq结合导致cAMP或(和) Ca2+水平的变化,实现信号转导。此外,果蝇神经系统内星型胶质细胞、瞬时感受器电位通道Waterwitch (Wtrw)以及多巴胺能神经元也参与TA的信号转导。TA参与昆虫求偶与交配后行为的调节,与章鱼胺(octopamine, OA)、FMIRFamide神经肽协同调节精子和卵的贮存和排放;还参与调节马氏管排泄,与多巴胺(dopamine, DA)协同调节蜜蜂工蜂的生殖分化,与OA以相互拮抗的方式调节昆虫的运动。飞蝗群居型和散居型个体的分化也受TA和OA的协同调节。TA还可以调节采集蜂资源利用与开发的平衡。现综述该领域相关研究进展并展望未来研究方向。

As a neuroactive substance in insects, tyramine(TA) is mainly synthesized in tyraminergic neurons, in addition, it can also be synthesized in the principal cells of the Malpighian tubule. There is TA transshipment occurring after TA binding its receptor to perform physiological functions, it can be transported back to the presynaptic membrane by transporters. N-acylation may be the main catabolic pathway of insect TA. Currently, the TA receptors found in insects all belong to G-protein-coupled receptors, which transduce signals by binding Gi or Gq to change the level of cAMP or(and) Ca2+. Moreover, stellate glial cells, transient receptor potential channel Waterwitch(Wtrw) and dopaminergic neurons in Drosophila nervous system are also involved in TA signal transduction. TA is involved in the regulation of courtship and postmating behavior of insects, and cooperates with octopamine(OA) and FMIRFamide neuropeptides to regulate the storage and discharge of sperm and eggs. TA also takes part in the regulation of Malpighian tubule excretion, cooperates with dopamine(DA) to regulate the reproductive differentiation of worker bees, and regulates insect movement in a mutually antagonistic way with OA. The transformation between the gregarious and the solitary individuals in Locusta is also involved in the coordinated regulation of TA and OA. In addition, TA can also regulate the balance between resource utilization and development of foraging individuals in honeybee. In this article, the related research progress was reviewed and the future research direction was prospected.