In the present work we describe the functional and molecular characterization of two Aedes aegypti allatostatin-C receptor paralogs (AeAS-CrA and AeAS-CrB) and provide a detailed quantitative study of the expression of the AS-C receptor genes in an adult insect. The tissue distribution of the two AS-C receptors differed significantly; the mRNA levels of AeAS-CrB in the Malpighian tubules were the highest detected, while transcripts for AeAS-CrA were relatively low in this tissue. In addition, the transcript levels of both receptors were different in the thoracic and abdominal ganglia, corpora allata (CA) and the testis of the male. In the CA, the AeAS-CrB mRNA levels were constant from 0 to 72 h after female emergence, while the AeAS-CrA levels increased at 72 h. To complement the receptor expression studies, we analyzed the tissue specificity for allatostatin-C mRNA in female mosquitoes. Expression was high in abdominal ganglia and brain. Transcript levels of allatostatin-C in the head of females were elevated at eclosion and there were no major changes during the first week of adult life or after blood feeding. Fluorometric Imaging Plate Reader (FLIPR) recordings of calcium transients in HEK293T cells transiently expressing both putative receptors showed that they both responded selectively to allatostatin-C stimulation in the nanomolar concentration range. However, the peptide showed slightly greater affinity for AeAS-CrB than AeAS-CrA. Our studies suggest that some of the pleiotropic effects of allatostatin-C in mosquitoes could be mediated by the different receptor paralogs. Transcriptional regulation of the AS-C receptors may not have a critical role in the changes of CA responsiveness to the peptide that we previously described.
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