title: Pharmacological characterization of a tyramine receptor from the southern cattle tick, Rhipicephalus (Boophilus) microplus.
abstract: The southern cattle tick (Rhipicephalus (Boophilus) microplus) is a hematophagous external parasite that vectors the causative agents of bovine babesiosis or cattle tick fever, Babesia bovis and B. bigemina, and anaplasmosis, Anaplasma marginale. The southern cattle tick is a threat to the livestock industry in many locations throughout the world. Control methods include the use of chemical acaricides including amitraz, a formamidine insecticide, which is proposed to activate octopamine receptors. Previous studies have identified a putative octopamine receptor from the southern cattle tick in Australia and the Americas. Furthermore, this putative octopamine receptor could play a role in acaricide resistance to amitraz. Recently, sequence data indicated that this putative octopamine receptor is probably a type-1 tyramine receptor (TAR1). In this study, the putative TAR1 was heterologously expressed in Chinese hamster ovary (CHO-K1) cells, and the expressed receptor resulted in a 39-fold higher potency for tyramine compared to octopamine. Furthermore, the expressed receptor was strongly antagonized by yohimbine and cyproheptadine, and mildly antagonized by mianserin and phentolamine. Tolazoline and naphazoline had agonistic or modulatory activity against the expressed receptor, as did the amitraz metabolite, BTS-27271; however, this was only observed in the presence of tyramine. The southern cattle tick's tyramine receptor may serve as a target for the development of anti-parasitic compounds, in addition to being a likely target of formamidine insecticides.
authors.affiliation: Pesticide Toxicology Laboratory, Department of Entomology, Iowa State University of Science and Technology, Ames IA 50011, USA; Department of Biomedical Science, Iowa State University of Science and Technology, Ames IA 50011, USA.
authors.forename: Aaron D
authors.initials: AD
authors.lastname: Gross
authors.affiliation: Knipling-Bushland United States Livestock Insects Research Laboratory and Veterinary Pest Genomics Center, United States Department of Agriculture-Agricultural Research Service, Kerrville, TX 78028, USA.
authors.forename: Kevin B
authors.initials: KB
authors.lastname: Temeyer
authors.affiliation: Department of Biomedical Science, Iowa State University of Science and Technology, Ames IA 50011, USA.
authors.forename: Tim A
authors.initials: TA
authors.lastname: Day
authors.affiliation: Knipling-Bushland United States Livestock Insects Research Laboratory and Veterinary Pest Genomics Center, United States Department of Agriculture-Agricultural Research Service, Kerrville, TX 78028, USA.
authors.forename: Adalberto A
authors.initials: AA
authors.lastname: Pérez de León
authors.affiliation: Department of Biomedical Science, Iowa State University of Science and Technology, Ames IA 50011, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Kimber
authors.affiliation: Pesticide Toxicology Laboratory, Department of Entomology, Iowa State University of Science and Technology, Ames IA 50011, USA. Electronic address: jcoats@iastate.edu.
authors.forename: Joel R
authors.initials: JR
authors.lastname: Coats
mesh_terms: D056810:Acaricides / Q000494:pharmacology; D000578:Amidines / Q000494:pharmacology; D000818:Animals; D016466:CHO Cells; D003412:Cricetulus; D003533:Cyproheptadine / Q000494:pharmacology; D009655:Octopamine / Q000378:metabolism; D017982:Receptors, Biogenic Amine / Q000037:antagonists & inhibitors / Q000378:metabolism*; D048494:Rhipicephalus / Q000378:metabolism*; D014052:Toluidines / Q000494:pharmacology; D014439:Tyramine / Q000378:metabolism*; D015016:Yohimbine / Q000494:pharmacology
chemical_list: D056810:Acaricides; D000578:Amidines; D017982:Receptors, Biogenic Amine; D014052:Toluidines; C027604:norsynephrine receptor; C066175:tyramine receptor; D009655:Octopamine; D015016:Yohimbine; D003533:Cyproheptadine; C025699:U 40481; C014983:amitraz; D014439:Tyramine
keywords: G-protein-coupled receptor; GPCR; Rhipicephalus microplus; Southern cattle tick; Tick; Tyramine receptor