Lentivirus mediated trophoblast specific Deptor knockdown increases transplacental system A and system L amino acid transport and fetal growth in mice.

Mechanistic target of rapamycin (mTOR) signaling is a positive regulator of human placental function including System A/L amino acid transport activity. Placental mTOR signaling is inhibited in fetal growth restriction (FGR) and activated in fetal overgrowth in women, however the causes of these changes in placental mTOR signaling are unknown. DEP-domain containing mTOR-interacting protein (DEPTOR) is an endogenous inhibitor of mTOR. We tested the hypothesis that trophoblast-specific Deptor knockdown activates placental mTOR signaling and amino acid transport and causes fetal overgrowth. Using lentiviral transduction of blastocyst trophectoderm with a small hairpin RNA, we achieved 47% knockdown of placental Deptor mRNA expression, without altering fetal Deptor mRNA expression. Trophoblast-specific Deptor knockdown activated placental mTORC1 and mTORC2 signaling and increased trophoblast plasma membrane (TPM) LAT1 and SNAT2 protein abundance, and TPM System L and System A transporter activity. In addition, Deptor knockdown increased in vivo transplacental System A and L amino acid transport and stimulated placental and fetal growth. In human FGR, placental DEPTOR protein expression was higher and negatively correlated with birth weight and microvillus plasma membrane System A activity. In conclusion, we provide mechanistic evidence that DEPTOR regulates placental mTOR signaling and amino acid transport and fetal growth in vivo. We speculate that modulation of placental Deptor is a promising target for intervention in pregnancies characterized by abnormal placental function and fetal growth.