Molecular cloning and expression of a type-two somatostatin receptor in goldfish brain and pituitary.
Somatostatin (SRIF or SS) exerts diverse inhibitory actions through binding to specific receptors. In this study, a SRIF receptor cDNA was cloned and sequenced from goldfish brain using PCR and cDNA library screening. The cDNA encodes a 380-amino acid goldfish type-two SRIF receptor (designated as sst(2)), with seven putative transmembrane domains (TMD) and YANSCANP motif in the seventh TMD, a signature sequence for the mammalian SRIF receptor (sst) family. In addition, the amino acid sequence of the receptor has 61-62% homology to mammalian sst(2), 41-47% homology to other mammalian sst subtypes and 41-43% homology to recently identified fish sst(1) and sst(3) receptors. Both SRIF-14 and [Pro(2)]SRIF-14, two of the native goldfish SRIF forms, but not a putative goldfish SRIF-28, significantly inhibited forskolin-stimulated adenosine 3':5'-cyclic monophosphate (cAMP) release in COS-7 cells transiently expressing goldfish sst(2), suggesting functional coupling of the receptor to adenylate cyclase. None of the three peptides affected inositol phosphate production in the same receptor expression system. Northern blot showed that mRNA for the sst(2) receptor is widely distributed in goldfish brain, and highly expressed in the pituitary. The decrease in pituitary sst(2) mRNA levels following estradiol implantation suggests the presence of a negative feedback mechanism on sst(2) gene expression.
Lin
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Department of Biological Sciences, University of Alberta, Alta, T6G 2E9, Edmonton, Canada.
Janovick
J A
JA
Cardenas
R
R
Conn
P M
PM
Peter
R E
RE
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D004958:Estradiol / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D006054:Goldfish / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D010802:Phylogeny; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017481:Receptors, Somatostatin / Q000737:chemistry / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D013739:Testosterone / Q000494:pharmacology
D017931:DNA Primers; D018076:DNA, Complementary; D012333:RNA, Messenger; D017481:Receptors, Somatostatin; D013739:Testosterone; D004958:Estradiol; C093733:somatostatin receptor 2