Maternal and Fetal Health Research Centre, Division of Developmental Biology and Medicine, St Mary's Hospital, Faculty of Biology, Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Manchester M13 9WL, UK.
Division of Cardiovascular Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Manchester M13 9NT, UK.
Placenta. 2021 Jan 1;103:188-198. doi: 10.1016/j.placenta.2020.10.034. Epub 2020 Oct 29.
Amino acid transport across the placenta is crucial for fetal growth. In rodent models, the visceral yolk sac (referred to as yolk sac hereafter) is also likely to contribute to fetal amino acid provision. System L amino acid transporters mediate the transport of essential amino acids. System L activity is mediated by light chains LAT1 (Slc7a5) and LAT2 (Slc7a8) which form functional complexes by heterodimeric linkage to CD98 (Slc3a2). LAT4 (Slc43a2) is monomeric, possessing overlapping amino acid substrate specificity with LAT1 and LAT2.
This study investigates the expression of these LAT subtypes in fetus-matched rat placenta and yolk sac.
Slc7a5, Slc7a8 and Slc43a2 transcripts were expressed in placenta and yolk sac with similar expression patterns between sexes. LAT1 expression was significantly higher in placenta than yolk sac. Conversely, LAT2 and LAT4 expression was significantly higher in yolk sac than placenta; CD98 expression was comparable. LAT1, LAT2, LAT4 and CD98 were distributed to rat placental labyrinth zone (LZ) and junctional zone (JZ). LAT1 and LAT4 demonstrated higher expression in LZ, whilst LAT2 was more intensely distributed to JZ. LAT1, LAT2, LAT4 and CD98 were expressed in yolk sac, with punctate LAT1 staining to endodermal cell cytoplasm, contrasting with the intense LAT2, LAT4 and CD98 endodermal cell basolateral distribution, accounting for greater LAT2 and LAT4 expression in yolk sac compared to placenta.
LAT1, LAT2 and LAT4 are expressed in rat placenta and yolk sac implicating a combined role for these LAT subtypes in supporting fetal growth and development.
氨基酸穿过胎盘的转运对于胎儿的生长至关重要。在啮齿动物模型中，内脏卵黄囊（以下简称卵黄囊）也可能有助于胎儿提供氨基酸。系统 L 氨基酸转运体介导必需氨基酸的转运。系统 L 的活性由轻链 LAT1（Slc7a5）和 LAT2（Slc7a8）通过异二聚体与 CD98（Slc3a2）形成功能性复合物来介导。LAT4（Slc43a2）是单体，与 LAT1 和 LAT2 具有重叠的氨基酸底物特异性。
本研究调查了这些 LAT 亚型在胎鼠胎盘和卵黄囊中表达。
Slc7a5、Slc7a8 和 Slc43a2 转录本在胎盘和卵黄囊中表达，性别间表达模式相似。LAT1 在胎盘中的表达显著高于卵黄囊。相反，LAT2 和 LAT4 在卵黄囊中表达显著高于胎盘；CD98 的表达相当。LAT1、LAT2、LAT4 和 CD98 分布于大鼠胎盘绒毛区（LZ）和连接区（JZ）。LAT1 和 LAT4 在 LZ 中的表达较高，而 LAT2 则更强烈地分布于 JZ。LAT1、LAT2、LAT4 和 CD98 在卵黄囊中表达，LAT1 呈点状染色，定位于内胚层细胞质，与 LAT2、LAT4 和 CD98 内胚层细胞基底外侧的强烈分布形成对比，这解释了与胎盘相比，卵黄囊中 LAT2 和 LAT4 表达更高的原因。
LAT1、LAT2 和 LAT4 在大鼠胎盘和卵黄囊中表达，提示这些 LAT 亚型在支持胎儿生长和发育方面具有共同作用。
