Molecular and pharmacological characterization of the Chelicerata pyrokinin receptor from the southern cattle tick, Rhipicephalus (Boophilus) microplus.
We identified the first pyrokinin receptor (Rhimi-PKR) in Chelicerata and analyzed structure-activity relationships of cognate ligand neuropeptides and their analogs. Based on comparative and phylogenetic analyses, this receptor, which we cloned from larvae of the cattle tick Rhipicephalus microplus (Acari: Ixodidae), is the ortholog of the insect pyrokinin (PK)/pheromone biosynthesis activating neuropeptide (PBAN)/diapause hormone (DH) neuropeptide family receptor. Rhimi-PKR functional analyses using calcium bioluminescence were performed with a developed stable recombinant CHO-K1 cell line. Rhimi-PKR was activated by four endogenous PKs from the Lyme disease vector, the tick Ixodes scapularis (EC50s range: 85.4 nM-546 nM), and weakly by another tick PRX-amide peptide, periviscerokinin (PVK) (EC50 = 24.5 μM). PK analogs with substitutions of leucine, isoleucine or valine at the C-terminus for three tick PK peptides, Ixosc-PK1, Ixosc-PK2, and Ixosc-PK3, retained their potency on Rhimi-PKR. Therefore, Rhimi-PKR is less selective and substantially more tolerant than insect PK receptors of C-terminal substitutions of leucine to isoleucine or valine, a key structural feature that serves to distinguish insect PK from PVK/CAP2b receptors. In females, ovary and synganglion had the highest Rhimi-PKR relative transcript abundance followed by the rectal sac, salivary glands, Malpighian tubules, and midgut. This is the first pharmacological analysis of a PK/PBAN/DH-like receptor from the Chelicerata, which will now permit the discovery of the endocrinological roles of this neuropeptide family in vectors of vertebrate pathogens.
Department of Entomology, Texas A&M University, College Station, TX 77843-2475, USA.
Yunlong
Y
Yang
Insect Control and Cotton Disease Research Unit, Southern Plains Agricultural Research Center, U.S. Department of Agriculture, College Station, TX 77845, USA.
Ronald J
RJ
Nachman
Department of Entomology, Texas A&M University, College Station, TX 77843-2475, USA. Electronic address: p-pietrantonio@tamu.edu.
Patricia V
PV
Pietrantonio
D000595:Amino Acid Sequence; D000818:Animals; D060829:Arthropod Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D005260:Female; D015870:Gene Expression; D008969:Molecular Sequence Data; D048494:Rhipicephalus / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D060829:Arthropod Proteins
Acari; Arthropod PRX-amide peptidomimetics; GPCR; Neuromedin U; Pyrokinin (PK)/pheromone biosynthesis activating neuropeptide (PBAN)/diapause hormone (DH); Tissue expression