PaOctβ2R: Identification and Functional Characterization of an Octopamine Receptor Activating Adenylyl Cyclase Activity in the American Cockroach Periplaneta americana

Abstract

Biogenic amines constitute an important group of neuroactive substances that control and modulate various neural circuits. These small organic compounds engage members of the guanine nucleotide-binding protein coupled receptor (GPCR) superfamily to evoke specific cellular responses. In addition to dopamine- and 5-hydroxytryptamine (serotonin) receptors, arthropods express receptors that are activated exclusively by tyramine and octopamine. These phenolamines functionally substitute the noradrenergic system of vertebrates Octopamine receptors that are the focus of this study are classified as either α- or β-adrenergic-like. Knowledge on these receptors is scarce for the American cockroach (Periplaneta americana). So far, only an α–adrenergic-like octopamine receptor that primarily causes Ca2+ release from intracellular stores has been studied from the cockroach (PaOctα1R). Here we succeeded in cloning a gene from cockroach brain tissue that encodes a β-adrenergic-like receptor and leads to cAMP production upon activation. Notably, the receptor is 100-fold more selective for octopamine than for tyramine. A series of synthetic antagonists selectively block receptor activity with epinastine being the most potent. Bioinformatics allowed us to identify a total of 19 receptor sequences that build the framework of the biogenic amine receptor clade in the American cockroach. Phylogenetic analyses using these sequences and receptor sequences from model organisms showed that the newly cloned gene is an β2-adrenergic-like octopamine receptor. The functional characterization of PaOctβ2R and the bioinformatics data uncovered that the monoaminergic receptor family in the hemimetabolic P. americana is similarly complex as in holometabolic model insects like Drosophila melanogaster and the honeybee, Apis mellifera. Thus, investigating these receptors in detail may contribute to a better understanding of monoaminergic signaling in insect behavior and physiology.

Pharmacological Properties and Function of the PxOctβ3 Octopamine Receptor in Plutella xylostella (L.)

“…Insect Octβ3Rs are specifically activated by either octopamine or tyramine, resulting in increased levels of intracellular cAMP [ 30 , 31 ]. Thus, corresponding experiments were conducted on transformed HEK293 cells that stably expressed PxOAB3.…”

Molecular and Pharmacological Characterization of β-Adrenergic-like Octopamine Receptors in the Endoparasitoid Cotesia chilonis (Hymenoptera: Braconidae)

“…To meet this opportunity, determining the molecular and pharmacological data of OAR subtypes is an important step. OARs have been characterized in D. melanogaster [ 33 , 40 , 54 ], Bombyx mori [ 55 , 56 ], Periplaneta americana [ 57 , 58 ], A. mellifera [ 41 , 59 , 60 ], N. lugens [ 42 , 49 ], and P. xylostella [ 43 , 46 , 61 , 62 ]. Here, we cloned three OARs from C. chilonis , investigated their expression profiles, and pharmacologically characterized them.…”

“…CcOctβRs belong to the class A GPCR family, which are supported by D 3.49 RY motif at the cytoplasmic of TM3 and N 7.49 PLIY in TM7 ( Supplementary Figures S1–S3 ). Most class A GPCRs are activated by ligands docking to specific amino acid residues in the receptor binding pocket close to the extracellular side [ 58 ], and functionally important residues of β-adrenergic-like OARs are highly conserved in CcOctβRs. The D 3.32 residue in TM3 (D 121 in CcOctβ1R, D 127 in CcOctβ2R, D 75 in CcOctβ3R), acts as an important residue that interacts with the protonated amino group of OA or TA.…”

Behavioral roles of biogenic amines in bumble bee males

“…Two µl of dopamine (Sigma-Aldrich) and octopamine (Sigma-Aldrich) solution (10 –4 , 10 –3 , and 10 –2 M) were dissolved in 0.1 M phosphate buffer (pH 7.0) or 2 µl of 0.1 M phosphate buffer (control). Epinastine (TCI, Tokyo, Japan, octopamine receptor antagonist 44 , 45 ) was dissolved in 0.1 M phosphate buffer to the concentration of 10 –2 M. To examine the roles of biogenic amines in the locomotion, light preference, and flight behaviors of bumble bee males, prepared solutions were injected into the abdomens of 4 day-old males using a 10-µL microsyringe with a fine needle. The duration of acclimatization was 15 min after drug injection before observing locomotor activities.…”