Lee Kyung Mi, Kaneko Toyoji, Aida Katsumi
Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657, Japan.
Gen Comp Endocrinol. 2006 May 1;146(3):318-28. doi: 10.1016/j.ygcen.2005.12.003. Epub 2006 Jan 23.
To investigate the physiological significance of prolactin (PRL) in a marine teleost, pufferfish (or fugu), Takifugu rubripes, we cloned and characterized cDNAs encoding its PRL and PRL receptor (PRLR) from the pituitary and gills, respectively. The fugu PRL cDNA consisted of 995 bp and encoded a protein of 213 amino acids. The PRLR, consisting of 510 amino acids, contained a putative signal peptide, an extracellular domain with two pairs of cysteines, a WSXWS motif, a single transmembrane domain, and a cytoplasmic (intracellular) domain with box 1 and box 2 regions, all of which are characteristic of the cytokine receptor superfamily. Reverse transcription-PCR showed the expression of PRLR mRNA in osmoregulatory organs, such as gills, kidney, and intestine, whereas pufferfish PRL mRNA was detected only in the pituitary. Furthermore, in situ hybridization revealed the expression of pufferfish PRLR in branchial chloride cells, kidney tubule cells, and intestinal epithelia. The PRL-gene expression levels in the pituitary were about five times higher in 25%-diluted seawater than in full-strength seawater. These results suggest that fugu PRL regulates water and electrolyte balances through PRLR expressed in the osmoregulatory organs, as is the case with freshwater-adapted euryhaline species.
为了研究催乳素（PRL）在海洋硬骨鱼河豚（Takifugu rubripes）中的生理意义，我们分别从垂体和鳃中克隆并鉴定了编码其PRL和PRL受体（PRLR）的cDNA。河豚PRL cDNA由995个碱基对组成，编码一个213个氨基酸的蛋白质。PRLR由510个氨基酸组成，包含一个推定的信号肽、一个带有两对半胱氨酸的细胞外结构域、一个WSXWS基序、一个单一跨膜结构域以及一个带有框1和框2区域的细胞质（细胞内）结构域，所有这些都是细胞因子受体超家族的特征。逆转录聚合酶链反应显示PRLR mRNA在鳃、肾脏和肠道等渗透调节器官中表达，而河豚PRL mRNA仅在垂体中检测到。此外，原位杂交显示河豚PRLR在鳃氯细胞、肾小管细胞和肠上皮中表达。垂体中PRL基因的表达水平在25%稀释海水中比在全强度海水中高约五倍。这些结果表明，河豚PRL通过在渗透调节器官中表达的PRLR来调节水和电解质平衡，就像适应淡水的广盐性物种一样。
