Lin X, Janovick J A, Cardenas R, Conn P M, Peter R E
Department of Biological Sciences, University of Alberta, Alta, T6G 2E9, Edmonton, Canada.
Mol Cell Endocrinol. 2000 Aug 30;166(2):75-87. doi: 10.1016/s0303-7207(00)00278-1.
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.
生长抑素（SRIF或SS）通过与特定受体结合发挥多种抑制作用。在本研究中，利用聚合酶链反应（PCR）和cDNA文库筛选技术，从金鱼脑中克隆并测序了一种SRIF受体cDNA。该cDNA编码一个380个氨基酸的金鱼Ⅱ型SRIF受体（命名为sst(2)），具有7个假定的跨膜结构域（TMD），且在第7个TMD中有YANSCANP基序，这是哺乳动物SRIF受体（sst）家族的特征序列。此外，该受体的氨基酸序列与哺乳动物sst(2)的同源性为61 - 62%，与其他哺乳动物sst亚型的同源性为41 - 47%，与最近鉴定的鱼类sst(1)和sst(3)受体的同源性为41 - 43%。金鱼天然的两种SRIF形式，即SRIF - 14和[Pro(2)]SRIF - 14，但推测的金鱼SRIF - 28则不然，它们能显著抑制在瞬时表达金鱼sst(2)的COS - 7细胞中由福斯可林刺激的腺苷3':5'-环磷酸（cAMP）释放，这表明该受体与腺苷酸环化酶存在功能偶联。在同一受体表达系统中，这三种肽均不影响肌醇磷酸的产生。Northern印迹分析表明，sst(2)受体的mRNA在金鱼脑中广泛分布，在垂体中高度表达。雌二醇植入后垂体sst(2) mRNA水平的降低表明存在对sst(2)基因表达的负反馈机制。
