Ogilvie S, Duckworth M L, Larkin L H, Buhi W C, Shiverick K T
Department of Pharmacology and Therapeutics, University of Florida, Gainesville 32610.
Endocrinology. 1990 May;126(5):2561-6. doi: 10.1210/endo-126-5-2561.
Mid- to late-gestation rat placenta expresses three PRL-related mRNAs, rat placental lactogen-II (rPL-II), rat PRL-like protein-A (rPLP-A), and rat PRL-like protein-B (rPLP-B). The protein product of rPL-II mRNA has been characterized, and the protein products of the rPLP-A mRNA were recently identified. The mol wt of a nonsecreted nonglycosylated rPLP-B protein would be 27,145 based on the mRNA sequence. The present study is the first to report the identification of the rPLP-B protein. Antiserum was generated against a chemically synthesized oligopeptide inferred from a specific region of the rPLP-B cDNA. Three or four distinct proteins synthesized and secreted by rat basal zone explants (day 15 gestation) showed cross-reactivity with the rPLP-B antiserum. The relative mol wt of these immunoreactive proteins is approximately 30,000, with a pI varying from 6.1-6.6. De novo synthesized rPLP-B proteins were not secreted by the explant tissue in the presence of tunicamycin, suggesting that the proteins are glycosylated. These data are consistent with the presence of one potential N-glycosylation site derived from the rPLP-B mRNA sequence. The rPLP-B antiserum showed no cross-reactivity with proteins identified using antisera against rPLP-A, rPL-II, or human pregnancy-specific beta 1-glycoprotein. Immunocytochemical studies were carried out using paraffin sections from placentas of day 14 and 17 pregnant rats which were treated with anti-rPLP-B, followed by avidin-biotin-peroxidase complex. These experiments show perinuclear staining, which was localized in basophilic cytotrophoblast cells, confirming previous in situ mRNA hybridization studies. Although no physiological role has been established for rPLP-B, the synthesis and secretion of this protein by cells in contact only with maternal circulation suggest a hormonal role.
妊娠中期至晚期的大鼠胎盘表达三种与催乳素相关的mRNA，即大鼠胎盘催乳素-II（rPL-II）、大鼠催乳素样蛋白-A（rPLP-A）和大鼠催乳素样蛋白-B（rPLP-B）。rPL-II mRNA的蛋白质产物已得到表征，rPLP-A mRNA的蛋白质产物最近也已被鉴定。根据mRNA序列，非分泌型非糖基化rPLP-B蛋白的分子量为27,145。本研究首次报道了rPLP-B蛋白的鉴定。针对从rPLP-B cDNA的特定区域推断出的化学合成寡肽产生了抗血清。大鼠基底部外植体（妊娠第15天）合成并分泌的三到四种不同蛋白质与rPLP-B抗血清表现出交叉反应性。这些免疫反应性蛋白的相对分子量约为30,000，pI在6.1 - 6.6之间变化。在衣霉素存在的情况下，外植体组织未分泌新合成的rPLP-B蛋白，这表明这些蛋白是糖基化的。这些数据与rPLP-B mRNA序列衍生的一个潜在N-糖基化位点的存在一致。rPLP-B抗血清与使用针对rPLP-A、rPL-II或人妊娠特异性β1-糖蛋白的抗血清鉴定的蛋白质无交叉反应性。使用来自妊娠第14天和17天大鼠胎盘的石蜡切片进行免疫细胞化学研究，先用抗rPLP-B处理，然后用抗生物素蛋白-生物素-过氧化物酶复合物处理。这些实验显示核周染色，其定位于嗜碱性细胞滋养层细胞，证实了先前的原位mRNA杂交研究。尽管尚未确定rPLP-B的生理作用，但仅与母体循环接触的细胞合成和分泌这种蛋白表明其具有激素作用。
