Institute of Biochemistry, Leipzig University, 04103 Leipzig, Germany.
Institute of Biological Information Processing, IBI-1, Research Center Jülich, 52428 Jülich, Germany.
Int J Mol Sci. 2020 Dec 8;21(24):9334. doi: 10.3390/ijms21249334.
The catecholamines norepinephrine and epinephrine are important regulators of vertebrate physiology. Insects such as honeybees do not synthesize these neuroactive substances. Instead, they use the phenolamines tyramine and octopamine for similar physiological functions. These biogenic amines activate specific members of the large protein family of G protein-coupled receptors (GPCRs). Based on molecular and pharmacological data, insect octopamine receptors were classified as either α- or β-adrenergic-like octopamine receptors. Currently, one α- and four β-receptors have been molecularly and pharmacologically characterized in the honeybee. Recently, an α-adrenergic-like octopamine receptor was identified in (DmOctα2R). This receptor is activated by octopamine and other biogenic amines and causes a decrease in intracellular cAMP ([cAMP]). Here, we show that the orthologous receptor of the honeybee (AmOctα2R), phylogenetically groups in a clade closely related to human α-adrenergic receptors. When heterologously expressed in an eukaryotic cell line, AmOctα2R causes a decrease in [cAMP]. The receptor displays a pronounced preference for octopamine over tyramine. In contrast to DmOctα2R, the honeybee receptor is not activated by serotonin. Its activity can be blocked efficiently by 5-carboxamidotryptamine and phentolamine. The functional characterization of AmOctα2R now adds a sixth member to this subfamily of monoaminergic receptors in the honeybee and is an important step towards understanding the actions of octopamine in honeybee behavior and physiology.
儿茶酚胺去甲肾上腺素和肾上腺素是脊椎动物生理学的重要调节剂。昆虫，如蜜蜂，不合成这些神经活性物质。相反，它们使用苯乙胺酪胺和章鱼胺来发挥类似的生理功能。这些生物胺激活了 G 蛋白偶联受体（GPCR）大家族中特定的成员。基于分子和药理学数据，昆虫章鱼胺受体被分类为α-或β-肾上腺素样章鱼胺受体。目前，在蜜蜂中已经分子和药理学上鉴定出一种α-和四种β-受体。最近，在 （DmOctα2R）中鉴定出一种α-肾上腺素样章鱼胺受体。该受体被章鱼胺和其他生物胺激活，导致细胞内 cAMP（[cAMP]）减少。在这里，我们表明，蜜蜂的同源受体（AmOctα2R）在系统发育上与人类α-肾上腺素受体密切相关。当在真核细胞系中异源表达时，AmOctα2R 导致 [cAMP] 减少。该受体对章鱼胺比对酪胺表现出明显的偏好。与 DmOctα2R 不同，蜜蜂受体不受血清素激活。5-羧基色胺和苯氧胺可以有效地阻断其活性。AmOctα2R 的功能表征现在为蜜蜂的单胺能受体亚家族增加了第六个成员，这是理解章鱼胺在蜜蜂行为和生理学中的作用的重要一步。
