The myokinins are invertebrate neuropeptides with myotropic and diuretic activity. The lymnokinin receptor from the snail Lymnaea stagnalis (Mollusca) has been the only previously identified myokinin receptor. We had cloned a G protein-coupled receptor (AF228521) from the tick Boophilus microplus (Arthropoda: Acari), 40% identical to the lymnokinin receptor, that we have now expressed in CHO-K1 cells. Myokinins at nanomolar concentrations induced intracellular calcium release, as measured by fluorescent cytometry and the receptor coupled to a pertussis toxin-insensitive G protein. Absence of extracellular calcium did not inhibit the fluorescence response, indicating that intracellular stores were sufficient for the initial response. Control cells only transfected with vector did not respond. We conclude that the tick receptor is the first myokinin receptor to be cloned from an arthropod.

Leucokinins are invertebrate neuropeptides that exhibit myotropic and diuretic activity. Only one leucokinin-like peptide receptor is known, the lymnokinin receptor from the mollusc Lymnaea stagnalis. A cDNA encoding a leucokinin-like peptide receptor was cloned from the Southern cattle tick, Boophilus microplus, a pest of cattle world-wide. This is the first neuropeptide receptor known from the Acari and the second known in the subfamily of leucokinin-like peptide G-protein-coupled receptors. The deduced amino acid sequence exhibits 40% identity to the lymnokinin receptor. The receptor transcript is present in all tick life stages as determined by semiquantitative reverse transcription polymerase chain reaction. We also propose that the sequence AAF50775.1 from the Drosophila melanogaster genome (CG10626) encodes the first identified insect leucokinin receptor.

A full-length cDNA encoding a 5-hydroxytryptamine (5-HT) receptor from the Southern cattle tick, Boophilus microplus, was isolated using a strategy based on sequence homology among G protein-coupled receptors. The deduced amino acid sequence revealed highest identity with Drosophila melanogaster 5HT-dro2A (Z11489, 50.8%) and 5HT-dro2B (Z11490, 49.5%) receptors. The receptor was transiently expressed in mammalian HEK293 cells, and Western blot analysis showed the expected 43.3 kDa band. In these cells, application of 5-HT (10 microm) inhibited forskolin-induced cAMP synthesis by 26%. The results indicate that the tick receptor is an invertebrate 5-HT1-like receptor that couples to Galphai protein.

We have cloned the fire ant glucose transporter 8 (GLUT8) cDNA providing the first molecular characterization of a GLUT8 in insects. Glucose is a poly-alcohol and, due to its high hydrophilicity, cannot move across cell membranes. GLUT8 is a putative facilitative transporter for the cellular import and export of glucose. The complete 2,974-bp cDNA encodes a 501-residue protein with a predicted molecular mass of 54.8 kDa. Transcripts were detected in the brain, midgut, hindgut, Malpighian tubule, fat body, ovary, and testis. The highest transcriptional expression was found in fat body. Northern blot analysis revealed different transcript sizes in mated queen brains, alate female ovaries, and male testes. We propose that four other sequences obtained from insect genome projects from the honey bee Apis mellifera (ENSAPMP00000006624), the malaria mosquito Anopheles gambiae (EAA11842), and the fruit fly Drosophila melanogaster (AAQ23604 and AAM52591) are likely the orthologues of the fire ant GLUT8. Phylogenetic relationships in insect glucose transporters are presented.

A cDNA encoding a putative aquaporin was cloned from the ovaries of the American dog tick, Dermacentor variabilis (Say) (Acari: Ixodidae). The encoded protein is most similar to the vertebrate aquaporin 9 protein family. Localization by reverse transcription-polymerase chain reaction (RT-PCR) shows expression in the gut and ovaries of adult females but not in the synganglion, Malpighian tubules, or salivary glands. Quantitative RT-PCR indicates that it is primarily expressed in the ovaries, with approximately 146 times more transcript than in the gut. When expressed in Xenopus oocytes, the aquaporin-like protein localized to the plasma membrane.