Molecular identification, transcript expression, and functional deorphanization of the adipokinetic...

The recently discovered adipokinetic hormone/corazonin-related peptide (ACP) is an insect neuropeptide structurally intermediate between corazonin (CRZ) and adipokinetic (AKH) hormones, which all demonstrate homology to the vertebrate gonadotropin-releasing hormone (GnRH). To date, the function of the ACP signaling system remains unclear. In the present study, we molecularly identified the complete open reading frame encoding the Aedes aegypti ACP receptor (ACPR), which spans nine exons and undergoes alternative splicing giving rise to three transcript variants. Only a single variant, AedaeACPR-I, yielding a deduced 577 residue protein, contains all seven transmembrane domains characteristic of rhodopsin-like G protein-coupled receptors. Functional deorphanization of AedaeACPR-I using a heterologous cell culture-based system revealed highly-selective and dose-dependent receptor activation by AedaeACP (EC₅₀ = 10.25 nM). Analysis of the AedaeACPR-I and AedaeACP transcript levels in all post-embryonic developmental stages using quantitative RT-PCR identified enrichment of both transcripts after adult eclosion. Tissue-specific expression profiling in adult mosquitoes reveals expression of the AedaeACPR-I receptor transcript in the central nervous system, including significant enrichment within the abdominal ganglia. Further, the AedaeACP transcript is prominently detected within the brain and thoracic ganglia. Collectively, these results indicate a neuromodulator or neurotransmitter role for ACP and suggest this neuropeptide may function in regulation of post-ecdysis activities.