title: Somatostatin-28 inhibitory action on somatolactin-α and -β gene expression in goldfish.
abstract: Somatostain (SS) is known to inhibit growth hormone (GH) and prolactin (PRL) secretion. Somatolactin (SL) is a member of the GH/PRL family, but its regulation by goldfish brain somatostatin-28 (gbSS-28) has not been examined. To this end, the structural identity of goldfish SLα was established by 5'/3'-rapid amplification of cDNA ends. As revealed by in situ hybridization and immunohistochemical staining, the expression of SL isoforms was detected in pituitary cells located in the neurointermediate lobe (NIL). The transcripts of goldfish SS receptor 5a (Sst5a) but not Sst1b, Sst2, or Sst3a were detected in the goldfish NIL cells by RT-PCR. In goldfish pituitary cells, gbSS-28 not only had an inhibitory effect on basal SLα and SLβ mRNA levels but also could abolish insulin-like growth factor-stimulated SL gene expression. In primary cultures of goldfish NIL cells, gbSS-28 reduced forskolin-stimulated total cAMP production. With the use of a pharmacological approach, the adenylate cyclase (AC)/cAMP and phospholipase C (PLC)/inositol trisphosphate (IP3)/protein kinase C (PKC) cascades were shown to be involved in gbSS-28-inhibited SLα mRNA expression. Similar postreceptor signaling cascades were also observed for gbSS-28-reduced SLβ mRNA expression, except that PKC coupling to PLC was not involved. These results provide evidence that gbSS-28 can inhibit SLα and SLβ gene expression at the goldfish pituitary level via Sst5 through differential coupling of AC/cAMP and PLC/IP3/PKC cascades.
authors.affiliation: Key Laboratory of Bio-resources and Eco-environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, Peoples Republic of China; and.
authors.forename: Quan
authors.initials: Q
authors.lastname: Jiang
authors.affiliation: School of Biological Sciences, The University of Hong Kong, Hong Kong, China olwong@hku.hk.
authors.forename: Anderson O L
authors.initials: AO
authors.lastname: Wong
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D003001:Cloning, Molecular; D000242:Cyclic AMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D029941:Fish Proteins / Q000235:genetics / Q000378:metabolism*; D006023:Glycoproteins / Q000235:genetics / Q000378:metabolism*; D006054:Goldfish / Q000235:genetics / Q000378:metabolism*; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D008969:Molecular Sequence Data; D010902:Pituitary Gland / Q000187:drug effects* / Q000378:metabolism; D010907:Pituitary Hormones / Q000235:genetics / Q000378:metabolism*; D061251:Primary Cell Culture; D011493:Protein Kinase C / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D017481:Receptors, Somatostatin / Q000819:agonists / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D053561:Somatostatin-28 / Q000494:pharmacology*; D013997:Time Factors; D010738:Type C Phospholipases / Q000378:metabolism
chemical_list: D029941:Fish Proteins; D006023:Glycoproteins; D010907:Pituitary Hormones; D012333:RNA, Messenger; D017481:Receptors, Somatostatin; C064448:somatolactin protein, fish; D053561:Somatostatin-28; D015544:Inositol 1,4,5-Trisphosphate; C094573:somatostatin receptor 5; D000242:Cyclic AMP; D011493:Protein Kinase C; D010738:Type C Phospholipases; D000262:Adenylyl Cyclases
keywords: goldfish brain somatostatin-28; goldfish pituitary cells; signaling pathways; somatolactin; somatostatin