Three distinct types of GnRH receptor characterized in the bullfrog.
It has been proposed recently that two types of GnRH receptors (GnRHR) exist in a particular species. Here we present data demonstrating that at least three types of GnRHR are expressed in a single diploid species, the bullfrog. Three different cDNAs, encoding distinct types of bullfrog GnRHR (bfGnRHR-1, bfGnRHR-2, and bfGnRHR-3), were isolated from pituitary and hindbrain of the bullfrog. BfGnRHR-1 mRNA was expressed predominantly in pituitary, whereas bfGnRHR-2 and -3 mRNAs were expressed in brain. The bfGnRHR-1, bfGnRHR-2, and bfGnRHR-3 proteins have an amino acid identity of approximately 30% to approximately 35% with mammalian GnRHRs and approximately 40% to approximately 50% with nonmammalian GnRHRs. Interestingly, bfGnRHR-2 has an 85% amino acid homology with Xenopus GnRHR. Less than 53% amino acid identity was observed among the three bfGnRHRs. All isolated cDNAs encode functional receptors because their transient expression in COS-7 cells resulted in a ligand-dependent increase in inositol phosphate production. Notably, all three receptors exhibited a differential ligand selectivity. For all receptors, cGnRH-II has a higher potency than mGnRH. In addition, salmon GnRH also has a strikingly high potency to stimulate all three receptors. In conclusion, we demonstrated the presence of three GnRHRs in the bullfrog. Their expression in pituitary and brain suggests that bfGnRHRs play an important role in the regulation of reproductive functions in the bullfrog.
Wang
L
L
Hormone Research Center and Department of Biology, Chonnam National University, Kwangju 500-757, Republic of Korea.
Bogerd
J
J
Choi
H S
HS
Seong
J Y
JY
Soh
J M
JM
Chun
S Y
SY
Blomenröhr
M
M
Troskie
B E
BE
Millar
R P
RP
Yu
W H
WH
McCann
S M
SM
Kwon
H B
HB
D000595:Amino Acid Sequence; D000818:Animals; D015139:Blotting, Southern; D019556:COS Cells; D003001:Cloning, Molecular; D017931:DNA Primers; D018076:DNA, Complementary / Q000235:genetics; D005786:Gene Expression Regulation; D006801:Humans; D007295:Inositol Phosphates / Q000378:metabolism; D008024:Ligands; D008969:Molecular Sequence Data; D010902:Pituitary Gland / Q000737:chemistry; D020033:Protein Isoforms / Q000737:chemistry / Q000145:classification / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011892:Rana catesbeiana / Q000235:genetics*; D011966:Receptors, LHRH / Q000737:chemistry / Q000145:classification* / Q000235:genetics / Q000378:metabolism*; D012249:Rhombencephalon / Q000737:chemistry; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D014162:Transfection
D017931:DNA Primers; D018076:DNA, Complementary; D007295:Inositol Phosphates; D008024:Ligands; D020033:Protein Isoforms; D012333:RNA, Messenger; D011966:Receptors, LHRH