Neuropeptides and neuropeptide receptors in the Drosophila melanogaster genome

Abstract

Recent genetic analyses in worms, flies, and mammals illustrate the importance of bioactive peptides in controlling numerous complex behaviors, such as feeding and circadian locomotion. To pursue a comprehensive genetic analysis of bioactive peptide signaling, we have scanned the recently completed Drosophila genome sequence for G protein-coupled receptors sensitive to bioactive peptides (peptide GPCRs). Here we describe 44 genes that represent the vast majority, and perhaps all, of the peptide GPCRs encoded in the fly genome. We also scanned for genes encoding potential ligands and describe 22 bioactive peptide precursors. At least 32 Drosophila peptide receptors appear to have evolved from common ancestors of 15 monophyletic vertebrate GPCR subgroups (e.g., the ancestral gastrin/cholecystokinin receptor). Six pairs of receptors are paralogs, representing recent gene duplications. Together, these findings shed light on the evolutionary history of peptide GPCRs, and they provide a template for physiological and genetic analyses of peptide signaling in Drosophila.

Figure 1

Neighbor-joining phylogenetic trees for the Family A, Group III-B receptors. For Family and Group classifications, see Kolakowski (1994) (see http://www.gcrdb.uthscsa.edu/). (A) Rooted tree for the gastrin/cholecystokinin (CCK) receptors. (B) Unrooted tree for the neurokinin receptors (NKRs) and related GPCRs. The midpoint of the tree is indicated with an “X.” (C)Unrooted tree for the neuropeptide Y (NPY) receptors (NPYRs) and prolactin releasing receptors (PRPRs). (D) Rooted tree for the bombesin/gastrin releasing peptide receptors. (E) Unrooted tree for the neuromedin U receptors (NMURs), growth hormone secretagogue receptors (GHSRs), neurotensin receptors (NTRs), thyrotropin releasing hormone receptors (TRFRs), and a large family of related orphan receptors from Caenorhabditis elegans. The C. elegans orphan receptors included here belong to one of three clades (classes A–C). (*) Omitted receptors are additional C. elegans orphan GPCRs; (**) omitted receptors are additional GHSRs and closely related orphan GPCRs. In A and D, a monophyletic set of 26 biogenic amine receptors (not shown) was used as the outgroup to determine the root of the trees (see Methods). In C and E, the location of the tree midpoint was ambiguous and is therefore not indicated. Portions of the trees representing groups of closely related receptors were omitted (the number of related receptors on each branch is indicated in parentheses). Drosophila GPCRs are listed in bold and italics. (BRS3) Bombesin receptor subtype 3; (BRS4) bombesin receptor subtype 4; (CCKR) CCK receptor type A; (CCKR XL) Xenopus laevis CCKR; (GASR) gastrin/CCK receptor type B; (GCRC) glucocorticoid-induced receptor; (GRL106) Lymnaea stagnalis cardioexcitatory receptor; (GRPR) gastrin releasing peptide (GRP) receptor; (LKR) Boophilus microplus (tick) leucokinin-like peptide receptor; (LSR) L. stagnalis lymnokinin receptor; (NFFR) neuropeptide FF/neuropeptide AF receptor; (NK1R–NK3R) NKR types 1–3; (NMU1R and NMU2R) neuromedin U receptor types 1 and 2; (NPR-1) product of the C. elegans npr-1 gene; (NPYRYA–NPYRYC) orphan zebrafish NPYRs; (NPYRB) Gadus morhua (Atlantic cod) NPYR; (NTR1 and NTR2) neurotensin receptor types 1 and 2; (NY1R–NY6R) NPY receptor types 1–6; (OT7T022) putative mammalian RFRP receptor; (OXR) orexin/hypocretin receptor; (STKR) Stomoxys calcitrans (stable fly) tachykinin receptor. The remaining non-Drosophila sequences are orphan GPCRs from C. elegans. Symbols denote bootstrap support, out of 1000 replicates, that was >500: (filled circles) >990; (open circles) >900; (open squares) >700; (open triangles) >500.

Figure 2

Neighbor-joining phylogenetic trees for the Family A, Group V receptors. (A) Rooted tree for the opioid, somatostatin, galanin, and allatostatin receptors. (B) Unrooted tree for the gonadotropin releasing hormone (GnRH), vasopressin, and oxytocin receptors. The likely midpoint of the tree is indicated with an “X.” (C) Rooted tree for the glycoprotein hormone receptors and related leucine-rich repeat containing receptors (LGRs). Bootstrap scores, omitted branches, and Drosophila GPCRs are indicated as in Fig. 1. (ALGR) Anthopleura elegantissima (sea anemone) LGR; (FSHR) follicle-stimulating hormone receptor; (GALR) galanin receptor type 1; (GALS) galanin receptor type 2; (GALT) galanin receptor type 3; (GPR24 and GPR54) mammalian orphan GPCRs; (GRHR) GnRH receptor; (ITR) isotocin receptor; (LGR4–7) LGR types 4–7; (LSCPR and LSCPR2) Lymnaea stagnalis conopressin receptor types 1 and 2; (LSHR) lutropin-choriogonadotropic hormone receptor; (MTR) mesotocin receptor; (NLGR) C. elegans LGR; (ORPH4) Lymnaea stagnalis orphan GPCR; (OPRD) delta-type opioid receptor; (OPRK) kappa-type opioid receptor; (OPRM) mu-type opioid receptor; (OPRX) nociceptin/orphanin FQ receptor; (OXYR) oxytocin receptor; (SLGR) L. stagnalis GRL101; (SSR1–SSR5) somatostatin receptor types 1–5; (TSHR) thyrotropin receptor; (V1AR and V1BR) vasopressin V1A and V1B receptors; (V2R) vasopressin V2 receptor; (VTR) vasostocin receptor. The remaining non-Drosophila sequences are orphan GPCRs from C. elegans.

Figure 3

Unrooted neighbor-joining tree for the Family B receptors. The location of the tree midpoint is ambiguous and is therefore not indicated. Bootstrap scores, omitted branches, and Drosophila GPCRs are indicated as in Fig. 1. The four groups of Family B receptors are indicated with vertical bars. (BAI) brain-specific angiogenesis inhibitors 1–3; (CALR) calcitonin receptor; (CAR1) cyclic AMP receptor 1; (CD97) leucocyte antigen CD97; (CGRR) calcitonin gene-related peptide type 1 receptor; (CRF2) corticotropin releasing factor (CRF) receptor 2; (CRFR) CRF receptor 1; (DIHR) diuretic hormone receptor; (EMR1) cell surface glycoprotein EMR1; (GIPR) gastric inhibitory polypeptide receptor; (GLP2R) glucagon-like peptide 2 receptor; (GLPR) glucagon-like peptide 1 receptor; (GLR) glucagon receptor; (GRFR) growth hormone releasing hormone receptor; (HE6) G protein-coupled receptor HE6; (LRP1–3) calcium-independent alpha-latrotoxin receptors (latrophilins) 1–3; (MEGF2) seven-pass transmembrane proteins CELSR1–2 and MEGF2; (PACR) pituitary adenylate cyclase activating polypeptide (PACAP) type I receptor; (PTR2) parathyroid hormone receptor; (PTRR) parathyroid hormone/parathyroid hormone-related peptide receptor; (SCRC) secretin receptor; (TM7XM1) human EGF-TM7 like protein; (VIPR) vasoactive intestinal polypeptide (VIP) receptor 1; (VIPS) VIP receptor 2. The remaining non-Drosophila sequences are orphan GPCRs from Caenorhaloditis elegans.