Key Laboratory of Bio-resources and Eco-environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, Peoples Republic of China; and.
School of Biological Sciences, The University of Hong Kong, Hong Kong, China
Am J Physiol Regul Integr Comp Physiol. 2014 Sep 15;307(6):R755-68. doi: 10.1152/ajpregu.00193.2014. Epub 2014 Jul 9.
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.
生长抑素（SS）已知可抑制生长激素（GH）和催乳素（PRL）的分泌。生长介素（SL）是 GH/PRL 家族的一员，但金鱼脑生长抑素-28（gbSS-28）对其的调节尚未被检测到。为此，通过 5'/3'-cDNA 末端快速扩增确定了金鱼 SLα 的结构同一性。通过原位杂交和免疫组织化学染色显示，SL 同工型的表达在位于神经中间叶（NIL）的垂体细胞中被检测到。通过 RT-PCR 在金鱼 NIL 细胞中检测到金鱼 SS 受体 5a（Sst5a）的转录本，但未检测到 Sst1b、Sst2 或 Sst3a。在金鱼垂体细胞中，gbSS-28 不仅对基础 SLα 和 SLβ mRNA 水平具有抑制作用，而且可以消除胰岛素样生长因子刺激的 SL 基因表达。在金鱼 NIL 细胞的原代培养物中，gbSS-28 降低了 forskolin 刺激的总 cAMP 产生。通过药理学方法，发现腺苷酸环化酶（AC）/cAMP 和磷脂酶 C（PLC）/三磷酸肌醇（IP3）/蛋白激酶 C（PKC）级联参与了 gbSS-28 抑制的 SLα mRNA 表达。对于 gbSS-28 降低的 SLβ mRNA 表达也观察到了类似的受体后信号级联，只是不涉及 PKC 与 PLC 的偶联。这些结果提供了证据，表明 gbSS-28 通过 Sst5 在金鱼垂体水平上可以通过不同的 AC/cAMP 和 PLC/IP3/PKC 级联来抑制 SLα 和 SLβ 基因的表达。
