Cloning and activation of the bullfrog apelin receptor: Gi/o coupling and high affinity for [Pro1]apelin-13.
In mammals, apelin and its G protein-coupled receptor, APJ, regulate blood pressure, intake of food and water, and cardiac contractility. In this study, we report the cloning and functional characterization of APJ in the bullfrog, Rana catesbeiana. Bullfrog APJ (bfAPJ) cDNA contains an open reading frame of 1083 nucleotides encoding a protein of 360 amino acid residues. Sequence alignment reveals 75% amino acid identity with Xenopus, 63% identity with zebrafish and 40-42% identity with mammalian APJs. RT-PCR analysis and tissue binding assay reveal high expression of bfAPJ mRNA in the brain, particularly in the hypothalamus, and moderate expression in the pituitary, testis, adrenal gland and lung. Whereas [pGlu(1)]apelin-13 did not induce CRE-luc (protein kinase A-specific reporter) and SRE-luc (protein kinase C-specific reporter) activity in cells expressing bfAPJ, this apelin-13 decreased forskolin-induced CRE-luc activity and cAMP accumulation in a pertussis toxin-sensitive manner. This study indicates that bfAPJ may couple to G(i/o). [Pro(1)]apelin-13, a synthetic apelin based on the sequence of the putative apelin gene from many non-mammalian species, activates bfAPJ with 5-10-fold greater sensitivity/affinity than mammalian apelin-13. Collectively, this study expands our understanding of the physiological roles of this receptor system in non-mammalian species.
Moon
Mi Jin
MJ
Laboratory of G Protein-Coupled Receptors, Korea University College of Medicine, Seoul 136-705, Republic of Korea.
Oh
Da Young
DY
Moon
Jung Sun
JS
Kim
Dong-Ki
DK
Hwang
Jong-Ik
JI
Lee
Ju Yeon
JY
Kim
Jae Il
JI
Cho
Sehyung
S
Kwon
Hyuk Bang
HB
Seong
Jae Young
JY
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D005260:Female; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism*; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism*; D008024:Ligands; D008297:Male; D008969:Molecular Sequence Data; D011392:Proline / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011892:Rana catesbeiana / Q000235:genetics*; D043562:Receptors, G-Protein-Coupled / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction