We here describe the cloning and characterization of the functionally active (Drm) FMRFamide receptor, which we designated as DrmFMRFa-R. cognate ligands for this orphan receptor, which we annotated as the Drm FMRFamide receptor or DrmFMRFa-R. Materials and Methods Cloning of the DrmFMRFa-R. The ORF of the orphan GPCR was amplified by PCR performed around the genomic Drm bacterial artificial chromosome clone, RPCI98-21A2 (GenBank accession no. AC010561), which contains the entire uninterrupted coding sequence of the CG2114 gene (1). Oligonucleotide PCR primers were designed to encompass the ORF. The forward and reverse primers had the following sequences: forward primer, 5-GGAATTCGCCACCATGAGTGGTACAGCGGTTGCG-3 and reverse primer, 5-GCTCTAGAGCCCGGACACAATCTCAGAATC-3. The forward primer also incorporates the Kozak sequence (GCCACC) to optimize the translation initiation (11), as well as an 569.28 yields pQPSQ/KDFMRFamide as sequence. (694.39 yields APPQ/KPSDNFL/IRFamide as sequence, a-, b-, y-, or z-type, and immonium (i) fragment ions are indicated. The theoretical fragmentCion masses found in the spectrum are underlined. pQ, pyroglutamic acid. In receptors and 16% sequence identity with the bovine TRH receptor (Fig. ?(Fig.1).1). All alignments were performed by using the alignx program (Informax, Oxford). Open in a separate window Fig 1. Alignment of the DrmFMRFa-R with the two most closely Gadodiamide kinase inhibitor related orphan receptors (F21C10.9 and C26F1.6) and with the bovine TRH receptor. Identical amino acids are highlighted in dark gray, conservative amino acids are in light gray, and the seven-membrane-spanning domains of DrmFMRFa-R are numbered ICVII. Dashed lines are spaces to optimize alignment. Distribution of DrmFMRFa-R. The receptor is present in all analyzed Drm larval organs, as well as in ovaries, heads, and bodies of adult fruit flies (Fig. ?(Fig.2).2). Tracheae also express the receptor. Therefore, expression in all tested organs may be attributed (at least partially) to the presence of internal tracheoles, which could not be removed during dissection. All samples in which reverse transcriptase was omitted were negative. Identification of a Neuropeptide Ligand. Cells expressing the Drm orphan receptor were challenged with fractions of the flesh travel CNS extract. Flesh travel, rather than fruit fly, extracts were used because of the starting material required: 4?105 Drm whole bodies (8), in contrast to 5,000 CNSs from Neb larvae, which are Gadodiamide kinase inhibitor relatively easy to dissect and hence require fewer purification steps. The closest related receptor for which a cognate ligand had been identified was the bovine TRH receptor (only 16% sequence homology). Thyroid hormones (T3 and T4) have Gadodiamide kinase inhibitor not yet been described in insects, and the receptor-expressing cells did not respond to bovine TRH in concentrations up to 10 M (data not shown). We used CNS extracts because we expected the ligand to be related to TRH, and TRH is usually predominantly present in the hypothalamus. Rabbit Polyclonal to GALR3 After assessing activity in the 0C60% acetonitrile fraction, we fractionated the peptide extract on an Xterra C8 column and tested the obtained 70 fractions for their ability to elicit a bioluminescent calcium response in CG2114-expressing CHO cells. Three areas of activity were found in eight fractions, suggesting the presence of more than one active ligand (Fig. ?(Fig.3).3). This response was not seen in CHO cells that were transfected with the empty pcDNA3 vector. Bioactive fractions were subjected to two further HPLC fractionations (Table ?(Table1)1) and testing until a single active peak was obtained. Open in a separate window Fig 3. Bioluminescence response in relative light units (RLU) of the DrmFMRFa-R-expressing CHO cells (gray bars) and of CHO/G16 cells that were transfected with the empty pcDNA3 vector (black bars) after addition of 0.3% of first column (C8) HPLC fractions (16 Neb CNS equivalents). Three areas of activity can be distinguished (fractions 35C37, 38C40, and 42C43), and these fractions were mutually pooled for further purification. The weak activity in fraction 21 was lost after further purification. Two fractions were obtained from which the two most prominent peaks at 569.28 and 694.39 were selected for fragmentation. The amino acid sequence of the peptides was decided to be pQPSQ/KDFMRFamide and APPQ/KPSDNFI/LRFamide (Fig. ?(Fig.4).4). Because MS/MS sequencing cannot distinguish between Leu and Ile (identical masses) or between Lys and Gln (mass difference of 0.04 Da), the second peptide was also subjected to automated Edman-based.