A novel subgroup of class I G-protein-coupled receptors.
Based on structural similarities of an expressed sequence tag with the platelet-activating factor (PAF) receptor a cDNA clone encoding a novel G-protein-coupled receptor (GPCR), named GPR34, was isolated from a human fetal brain cDNA library. Genomic DNA analyses revealed the receptor to be encoded by an intronless single-copy gene at Xp11. 3-11.4. The predicted 381-amino-acid protein disclosed all structural features characteristic of a member of the class I GPCR family. Except an obvious sequence homology in transmembrane domain 6, no further similarities to the PAF receptor or any other known GPCR were found. The corresponding mouse receptor DNA was isolated from a genomic P1 library displaying a 90% amino acid identity compared to the human receptor. Phylogenetic studies showed that GPR34 is preserved among vertebrates, and the existence of GPR34 subtypes was demonstrated. The receptor mRNA is abundantly expressed in human and mouse tissues. In addition to the major 2-kb transcript, a 4-kb transcript was found only in mouse liver and testis. Expression of the human GPR34 in COS-7 cells followed by Western blot studies revealed specific bands of a highly glycosylated protein between 75 and 90 kDa. A number of potential ligands including phospholipids, leukotrienes, hydroxy-eicosatetraenoic acids, nucleotides and peptides were tested in functional assays. Since none of the applied substances led to significant changes in second messenger levels (cAMP and inositol phosphates), the natural ligand and coupling profile of this novel GPCR subgroup remains unknown.
Institut für Pharmakologie, Universitätsklinikum Benjamin Franklin, Freie Universität Berlin, Thielallee 69-73, D-14195, Berlin, Germany. schoberg@zedat.fu-berlin.de
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T
Schöneberg
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A
Schulz
R
R
Grosse
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R
Schade
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P
Henklein
G
G
Schultz
T
T
Gudermann
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001921:Brain / Q000196:embryology / Q000378:metabolism; D019556:COS Cells; D003001:Cloning, Molecular; D019204:GTP-Binding Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation; D015723:Gene Library; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D010802:Phylogeny; D010980:Platelet Membrane Glycoproteins / Q000737:chemistry / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D011956:Receptors, Cell Surface / Q000145:classification* / Q000235:genetics / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled; D049312:Receptors, Lysophospholipid; D018048:Receptors, Purinergic P2 / Q000737:chemistry / Q000235:genetics; D016415:Sequence Alignment
C118065:G-protein-coupled receptor 34; D010980:Platelet Membrane Glycoproteins; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D049312:Receptors, Lysophospholipid; D018048:Receptors, Purinergic P2; C039351:platelet activating factor receptor; D019204:GTP-Binding Proteins