Rhodopsin-like receptors

Rhodopsin-like receptors are a family of proteins that comprise the largest group of G protein-coupled receptors.

Scope
G-protein-coupled receptors, GPCRs, constitute a vast protein family that encompasses a wide range of functions (including various autocrine, paracrine, and endocrine processes). They show considerable diversity at the sequence level, on the basis of which they can be separated into distinct groups. GPCRs are usually described as "superfamily" because they embrace a group of families for which there are indications of evolutionary relationship, but between which there is no statistically significant similarity in sequence. The currently known superfamily members include the rhodopsin-like GPCRs (this family), the secretin-like GPCRs, the cAMP receptors, the fungal mating pheromone receptors, and the metabotropic glutamate receptor family. There is a specialised database for GPCRs.

Function
The rhodopsin-like GPCRs themselves represent a widespread protein family that includes hormone, neuropeptide, neurotransmitter, and light receptors, all of which transduce extracellular signals through interaction with guanine nucleotide-binding (G) proteins. Although their activating ligands vary widely in structure and character, the amino acid sequences of the receptors are very similar and are believed to adopt a common structural framework comprising 7 transmembrane (TM) helices.

Classes
Rhodopsin-like GPCRs have been classified into the following 19 subgroups (A1-A19) based on a phylogenetic analysis.

Subfamily A1

 * Chemokine receptor
 * Chemokine (C-C motif) receptor 1 (, CKR1)
 * Chemokine (C-C motif) receptor 2 (, CKR2)
 * Chemokine (C-C motif) receptor 3 (, CKR3)
 * Chemokine (C-C motif) receptor 4 (, CKR4)
 * Chemokine (C-C motif) receptor 5 (, CKR5)
 * Chemokine (C-C motif) receptor 8 (, CKR8)
 * Chemokine (C-C motif) receptor-like 2 (, CKRX)
 * chemokine (C motif) receptor 1 (, CXC1)
 * chemokine (C-X3-C motif) receptor 1 (, C3X1)
 * GPR137B (, TM7SF1)

Subfamily A2

 * Chemokine receptor
 * Chemokine (C-C motif) receptor-like 1 (, CCR11)
 * Chemokine (C-C motif) receptor 6 (, CKR6)
 * Chemokine (C-C motif) receptor 7 (, CKR7)
 * Chemokine (C-C motif) receptor 9 (, CKR9)
 * Chemokine (C-C motif) receptor 10 (, CKRA)
 * CXC chemokine receptors
 * Chemokine (C-X-C motif) receptor 3
 * Chemokine (C-X-C motif) receptor 4 (, Fusin)
 * Chemokine (C-X-C motif) receptor 5
 * Chemokine (C-X-C motif) receptor 6 (, BONZO)
 * Chemokine (C-X-C motif) receptor 7 (, RDC1)
 * Interleukin-8 (IL8R)
 * IL8R-α (, CXCR1)
 * IL8R-β (, CXCR2)
 * Adrenomedullin receptor
 * Duffy blood group, chemokine receptor (, DUFF)
 * G Protein-coupled Receptor 30 (, CML2, GPCR estrogen receptor)

Subfamily A3

 * Angiotensin II receptor
 * Angiotensin II receptor, type 1 (, AG2S)
 * Angiotensin II receptor, type 2 (, AG22)
 * Apelin receptor (, APJ)
 * Bradykinin receptor
 * Bradykinin receptor B1 (, BRB1)
 * Bradykinin receptor B2 (, BRB2)
 * GPR15 (, GPRF)
 * GPR25

Subfamily A4

 * Opioid receptor
 * delta Opioid receptor (, OPRD)
 * kappa Opioid receptor (, OPRK)
 * mu Opioid receptor (, OPRM)
 * Nociceptin receptor (, OPRX)
 * Somatostatin receptor
 * Somatostatin receptor 1 (, SSR1)
 * Somatostatin receptor 2 (, SSR2)
 * Somatostatin receptor 3 (, SSR3)
 * Somatostatin receptor 4 (, SSR4)
 * Somatostatin receptor 5 (, SSR5)
 * GPCR neuropeptide receptor
 * Neuropeptides B/W receptor 1 (, GPR7)
 * Neuropeptides B/W receptor 2 (, GPR8)
 * GPR1 orphan receptor

Subfamily A5

 * Galanin receptor
 * Galanin receptor 1 (, GALR)
 * Galanin receptor 2 (, GALS)
 * Galanin receptor 3 (, GALT)
 * Cysteinyl leukotriene receptor
 * Cysteinyl leukotriene receptor 1
 * Cysteinyl leukotriene receptor 2
 * Leukotriene B4 receptor
 * Leukotriene B4 receptor (, P2Y7)
 * Leukotriene B4 receptor 2
 * Relaxin receptor
 * Relaxin/insulin-like family peptide receptor 1 (, LGR7)
 * Relaxin/insulin-like family peptide receptor 2 (, GPR106)
 * Relaxin/insulin-like family peptide receptor 3 (, SALPR)
 * Relaxin/insulin-like family peptide receptor 4 (, GPR100/GPR142)
 * KiSS1-derived peptide receptor (GPR54)
 * Melanin-concentrating hormone receptor 1 (, GPRO)
 * Urotensin-II receptor (, UR2R)

Subfamily A6

 * Cholecystokinin receptor
 * Cholecystokinin A receptor (, CCKR)
 * Cholecystokinin B receptor (, GASR)
 * Neuropeptide FF receptor
 * Neuropeptide FF receptor 1 (, FF1R)
 * Neuropeptide FF receptor 2 (, FF2R)
 * Orexin receptor
 * Hypocretin (orexin) receptor 1 (, OX1R)
 * Hypocretin (orexin) receptor 2 (, OX2R)
 * Vasopressin receptor
 * Arginine vasopressin receptor 1A (, V1AR)
 * Arginine vasopressin receptor 1B (, V1BR)
 * Arginine vasopressin receptor 2 (, V2R)
 * Oxytocin receptor
 * Gonadotropin releasing hormone receptor (, GRHR)
 * Pyroglutamylated RFamide peptide receptor (, GPR103)
 * GPR22 (, GPRM)
 * GPR176 (, GPR)

Subfamily A7

 * Bombesin receptor
 * Bombesin-like receptor 3
 * Neuromedin B receptor
 * Gastrin-releasing peptide receptor
 * Endothelin receptor
 * Endothelin receptor type A (, ET1R)
 * Endothelin receptor type B (, ETBR)
 * GPR37 (, ETBR-LP2)
 * Neuromedin U receptor
 * Neuromedin U receptor 1
 * Neuromedin U receptor 2
 * Neurotensin receptor
 * Neurotensin receptor 1 (, NTR1)
 * Neurotensin receptor 2 (, NTR2)
 * Thyrotropin-releasing hormone receptor (, TRFR)
 * Growth hormone secretagogue receptor
 * GPR39
 * Motilin receptor (, GPR38)

Subfamily A8

 * Anaphylatoxin receptors
 * C3a receptor (, C3AR)
 * C5a receptor (, C5AR)
 * Chemokine-like receptor 1 (, CML1)
 * Formyl peptide receptor
 * Formyl peptide receptor 1 (, FMLR)
 * Formyl peptide receptor-like 1 (, FML2)
 * Formyl peptide receptor-like 2 (, FML1)
 * MAS1 oncogene
 * MAS1 (, MAS)
 * MAS1L (, MRG)
 * GPR1
 * GPR32 (, GPRW)
 * GPR44
 * GPR77 (, C5L2)

Subfamily A9

 * Melatonin receptor
 * Melatonin receptor 1A (, ML1A)
 * Melatonin receptor 1B (, ML1B)
 * Neurokinin receptor
 * Tachykinin receptor 1 (, NK1R)
 * Tachykinin receptor 2 (, NK2R)
 * Tachykinin receptor 3 (, NK3R)
 * Neuropeptide Y receptor
 * Neuropeptide Y receptor Y1 (, NY1R)
 * Neuropeptide Y receptor Y2 (, NY2R)
 * Pancreatic polypeptide receptor 1 (, NY4R)
 * Neuropeptide Y receptor Y5 (, NY5R)
 * Prolactin-releasing peptide receptor (PRLHR, GPRA)
 * Prokineticin receptor 1 (, GPR73)
 * Prokineticin receptor 2 (, PKR2)
 * GPR19 (, GPRJ)
 * GPR50 (, ML1X)
 * GPR75
 * GPR83 (, GPR72)

Subfamily A10

 * Glycoprotein hormone receptor
 * FSH-receptor
 * Luteinizing hormone/choriogonadotropin receptor (, LSHR)
 * Thyrotropin receptor
 * Leucine-rich repeat-containing G protein-coupled receptor 4 (, GPR48)
 * Leucine-rich repeat-containing G protein-coupled receptor 5 (, GPR49)
 * Leucine-rich repeat-containing G protein-coupled receptor 6

Subfamily A11

 * GPR40-related receptor
 * Free fatty acid receptor 1 (, GPR40)
 * Free fatty acid receptor 2 (, GPR43)
 * Free fatty acid receptor 3 (, GPR41)
 * GPR42 (, FFAR1L)
 * P2 purinoceptor
 * Purinergic receptor P2Y1
 * Purinergic receptor P2Y2
 * Purinergic receptor P2Y4
 * Purinergic receptor P2Y6
 * Purinergic receptor P2Y8
 * Purinergic receptor P2Y11
 * Hydroxycarboxylic acid receptor 1 (, GPR81)
 * Hydroxycarboxylic acid receptor 2, Niacin receptor 1 (, GPR109A)
 * Hydroxycarboxylic acid receptor 3, Niacin receptor 2 (, GPR109B, HM74)
 * GPR31 (, GPRV)
 * GPR82
 * Oxoglutarate (alpha-ketoglutarate) receptor 1 (, GPR80)
 * Succinate receptor 1 (, GPR91)

Subfamily A12

 * P2 purinoceptor
 * Purinergic receptor P2Y12
 * Purinergic receptor P2Y13 (, GPR86)
 * Purinergic receptor P2Y14 (, UDP-glucose receptor, KI01)
 * GPR34
 * GPR87
 * GPR171 (, H963)
 * Platelet-activating factor receptor (, PAFR)

Subfamily A13

 * Cannabinoid receptor
 * Cannabinoid receptor 1 (brain) (, CB1R)
 * Cannabinoid receptor 2 (macrophage) (, CB2R)
 * Lysophosphatidic acid receptor
 * Lysophosphatidic acid receptor 1
 * Lysophosphatidic acid receptor 2
 * Lysophosphatidic acid receptor 3
 * Sphingosine 1-phosphate receptor
 * Sphingosine 1-phosphate receptor 1
 * Sphingosine 1-phosphate receptor 2
 * Sphingosine 1-phosphate receptor 3
 * Sphingosine 1-phosphate receptor 4
 * Sphingosine 1-phosphate receptor 5
 * Melanocortin/ACTH receptor
 * Melanocortin 1 receptor (, MSHR)
 * Melanocortin 3 receptor
 * Melanocortin 4 receptor
 * Melanocortin 5 receptor
 * ACTH receptor, ACTR)
 * GPR3
 * GPR6
 * GPR12 (, GPRC)

Subfamily A14

 * Eicosanoid receptor
 * Prostaglandin D2 receptor (, PD2R)
 * Prostaglandin E1 receptor (, PE21)
 * Prostaglandin E2 receptor (, PE22)
 * Prostaglandin E3 receptor (, PE23)
 * Prostaglandin E4 receptor (, PE24)
 * Prostaglandin F receptor (, PF2R)
 * Prostaglandin I2 (prostacyclin) receptor (, PI2R)
 * Thromboxane A2 receptor (, TA2R)

Subfamily A15

 * Lysophosphatidic acid receptor
 * Lysophosphatidic acid receptor 4
 * Lysophosphatidic acid receptor 5
 * Lysophosphatidic acid receptor 6
 * P2 purinoceptor
 * Purinergic receptor P2Y10 (, P2Y10)
 * Protease-activated receptor
 * Coagulation factor II (thrombin) receptor-like 1 (, PAR2)
 * Coagulation factor II (thrombin) receptor-like 2 (, PAR3)
 * Coagulation factor II (thrombin) receptor-like 3 (, PAR4)
 * Epstein-Barr virus induced gene 2 (lymphocyte-specific G protein-coupled receptor)
 * Proton-sensing G protein-coupled receptors
 * GPR4
 * GPR65
 * GPR68
 * GPR132 (, G2A)
 * GPR17 (, GPRH)
 * GPR18 (, GPRI)
 * GPR20 (, GPRK)
 * GPR35
 * GPR55
 * Coagulation factor II receptor (, THRR)

Subfamily A16

 * Opsins
 * Rhodopsin (, OPSD)
 * Opsin 1 (cone pigments), short-wave-sensitive (color blindness, tritan) (, OPSB) (blue-sensitive opsin)
 * Opsin 1 (cone pigments), medium-wave-sensitive (color blindness, deutan) (, OPSG) (green-sensitive opsin)
 * Opsin 1 (cone pigments), long-wave-sensitive (color blindness, protan) (, OPSR) (red-sensitive opsin)
 * Opsin 3, Panopsin
 * Opsin 4, Melanopsin
 * Opsin 5 (, GPR136)
 * Retinal G protein coupled receptor
 * Retinal pigment epithelium-derived rhodopsin homolog (, OPSX) (visual pigment-like receptor opsin)

Subfamily A17

 * 5-Hydroxytryptamine (5-HT) receptor
 * 5-HT2A (, 5H2A)
 * 5-HT2B (, 5H2B)
 * 5-HT2C (, 5H2C)
 * 5-HT6 (, 5H6)
 * Adrenergic receptor
 * Alpha1A (, A1AA)
 * Alpha1B (, A1AB)
 * Alpha1D (, A1AD)
 * Alpha2A (, A2AA)
 * Alpha2B (, A2AB)
 * Alpha2C (, A2AC)
 * Beta1 (, B1AR)
 * Beta2 (, B2AR)
 * Beta3 (, B3AR)
 * Dopamine receptor
 * D1 (, DADR)
 * D2 (, D2DR)
 * D3 (, D3DR)
 * D4 (, D4DR)
 * D5 (, DBDR)
 * Trace amine receptor
 * TAAR1 (, TAR1)
 * TAAR2 (, GPR58)
 * TAAR3 (, GPR57)
 * TAAR5 (, PNR)
 * TAAR6 (, TAR4)
 * TAAR8 (, GPR102)
 * TAAR9 (, TAR3)
 * Histamine H2 receptor (, HH2R)

Subfamily A18

 * Histamine H1 receptor (, HH1R)
 * Histamine H3 receptor
 * Histamine H4 receptor
 * Adenosine receptor
 * A1 (, AA1R)
 * A2a (, AA2A)
 * A2b (, AA2B)
 * A3 (, AA3R)
 * Muscarinic acetylcholine receptor
 * M1 (, ACM1)
 * M2 (, ACM2)
 * M3 (, ACM3)
 * M4 (, ACM4)
 * M5 (, ACM5)
 * GPR21 (, GPRL)
 * GPR27
 * GPR45 (, PSP24)
 * GPR52
 * GPR61
 * GPR62
 * GPR63
 * GPR78
 * GPR84
 * GPR85
 * GPR88
 * GPR101
 * GPR161 (, RE2)
 * GPR173 (, SREB3)

Subfamily A19

 * 5-Hydroxytryptamine (5-HT) receptor
 * 5-HT1A (, 5H1A)
 * 5-HT1B (, 5H1B)
 * 5-HT1D (, 5H1D)
 * 5-HT1E (, 5H1E)
 * 5-HT1F (, 5H1F)
 * 5-HT4
 * 5-HT5A (, 5H5A)
 * 5-HT7 (, 5H7)

Unclassified

 * Olfactory receptor
 * Nematode chemoreceptor (multiple, including )
 * Taste receptor type 2
 * Vomeronasal receptor type 1
 * VN1R1
 * VN1R2
 * VN1R3
 * VN1R4
 * VN1R5