Udagawa K, Miyagi Y, Hirahara F, Miyagi E, Nagashima Y, Minaguchi H, Misugi K, Yasumitsu H, Miyazaki K
Department of Obstetrics, Yokohama City University School of Medicine, Yokohama, Japan.
Placenta. 1998 Mar-Apr;19(2-3):217-23. doi: 10.1016/s0143-4004(98)90011-x.
Placental protein 5 (PP5) is a placenta-derived glycoprotein with serine proteinase-inhibiting activity. To date its physiological functions have not been well elucidated. Recently, cDNA sequence analysis revealed that PP5 belongs to the Kunitz-type proteinase inhibitor family and it is identical to tissue factor pathway inhibitor-2 (TFPI-2), homologous to TFPI. Northern blot analysis demonstrated that placental tissue is extremely rich in the transcripts. This study localized PP5/TFPI-2 mRNA in placental tissues at three different gestational periods using in situ hybridization. PP5/TFPI-2 mRNA was specifically detected in syncytiotrophoblast at any gestational period examined, suggesting that syncytiotrophoblast is the principal production site of PP5/TFPI-2 in developing placental tissues. This mRNA expression pattern of PP5/TFPI-2 is quite different from that of TFPI, which is mainly found in vascular endothelial cells. The results indicated possible roles of PP5/TFPI-2 in the trophoblast differentiation and in the maintenance of intervillous blood flow. Also, Northern analysis demonstrated no or little expression of PP5/TFPI-2 in four choriocarcinoma cell lines, in contrast to its abundant expression in syncytiotrophoblast.
胎盘蛋白5（PP5）是一种源自胎盘的糖蛋白，具有丝氨酸蛋白酶抑制活性。迄今为止，其生理功能尚未得到充分阐明。最近，cDNA序列分析表明，PP5属于Kunitz型蛋白酶抑制剂家族，与组织因子途径抑制剂-2（TFPI-2）相同，与TFPI同源。Northern印迹分析表明，胎盘组织中的转录本极为丰富。本研究采用原位杂交技术，对三个不同孕期胎盘组织中的PP5/TFPI-2 mRNA进行了定位。在任何检测的孕期，均在合体滋养层中特异性检测到PP5/TFPI-2 mRNA，这表明合体滋养层是发育中胎盘组织中PP5/TFPI-2的主要产生部位。PP5/TFPI-2的这种mRNA表达模式与主要存在于血管内皮细胞中的TFPI截然不同。结果表明，PP5/TFPI-2在滋养层分化和绒毛间隙血流维持中可能发挥作用。此外，Northern分析表明，与合体滋养层中PP5/TFPI-2的丰富表达相比，四种绒毛膜癌细胞系中该基因无表达或几乎无表达。
