Hu Guangfu, He Mulan, Ko Wendy K W, Wong Anderson O L
College of Fisheries, Huazhong Agricultural University, Wuhan 430070, China.
School of Biological Sciences, University of Hong Kong, Hong Kong, China.
Endocrinology. 2017 Jun 1;158(6):1776-1797. doi: 10.1210/en.2016-1740.
Tachykinin-1 (TAC1) is known to have diverse functions in mammals, but similar information is scarce in fish species. Using grass carp as a model, the pituitary actions, receptor specificity and postreceptor signaling of TAC1 gene products, namely substance P (SP) and neurokinin A (NKA), were examined. TAC1 encoding SP and NKA as well as tachykinin receptors NK1R and NK2R were cloned in the carp pituitary. The newly cloned receptors were shown to be functional with properties similar to mammalian counterparts. In carp pituitary cells, SP and NKA could trigger luteinizing hormone (LH), prolactin (PRL), and somatolactin α (SLα) secretion, with parallel rises in PRL and SLα transcripts. Short-term SP treatment (3 hours) induced LH release, whereas prolonged induction (24 hours) could attenuate LHβ messenger RNA (mRNA) expression. At pituitary cell level, LH, PRL, and SLα regulation by TAC1 gene products were mediated by NK1R, NK2R, and NK3R, respectively. Apparently, SP- and NKA-induced LH and SLα secretion and transcript expression were mediated by adenylyl cyclase/cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA), phospholiphase C (PLC)/inositol 1,4,5-triphosphate/protein kinase C (PKC), and Ca2+/calmodulin (CaM)/CaM-dependent protein kinase-II pathways. The signal transduction for PRL responses was similar, except for the absence of a PKC component. Regarding SP inhibition of LHβ mRNA expression, the cAMP/PKA- and PLC/PKC-dependent (but not Ca2+/CaM-dependent) cascades were involved. These results, as a whole, suggest that TAC1 gene products play a role in LH, PRL, and SLα regulation via overlapping postreceptor signaling coupled to different subtypes of tachykinin receptor expressed in the carp pituitary.
速激肽-1（TAC1）在哺乳动物中具有多种功能，但在鱼类中的相关信息却很少。以草鱼为模型，研究了TAC1基因产物即P物质（SP）和神经激肽A（NKA）的垂体作用、受体特异性和受体后信号传导。编码SP和NKA的TAC1以及速激肽受体NK1R和NK2R在鲤鱼垂体中被克隆。新克隆的受体显示具有功能，其特性与哺乳动物的对应受体相似。在鲤鱼垂体细胞中，SP和NKA可触发促黄体生成素（LH）、催乳素（PRL）和生长抑素α（SLα）的分泌，同时PRL和SLα转录本平行增加。短期SP处理（3小时）诱导LH释放，而长期诱导（24小时）可减弱LHβ信使核糖核酸（mRNA）的表达。在垂体细胞水平，TAC1基因产物对LH、PRL和SLα的调节分别由NK1R、NK2R和NK3R介导。显然，SP和NKA诱导的LH和SLα分泌及转录本表达是由腺苷酸环化酶/环磷酸腺苷（cAMP）/蛋白激酶A（PKA）、磷脂酶C（PLC）/肌醇1,4,5-三磷酸/蛋白激酶C（PKC）以及Ca2+/钙调蛋白（CaM）/CaM依赖性蛋白激酶-II途径介导的。PRL反应的信号转导类似，只是没有PKC成分。关于SP对LHβ mRNA表达的抑制作用，涉及cAMP/PKA和PLC/PKC依赖性（但不涉及Ca2+/CaM依赖性）级联反应。总体而言，这些结果表明TAC1基因产物通过与鲤鱼垂体中表达的不同亚型速激肽受体偶联的重叠受体后信号传导，在LH、PRL和SLα的调节中发挥作用。
