Lentivirus-Mediated Trophoblast-Specific <i>Deptor</i> 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 (Dishevelled, Egl-10, Pleckstrin) 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 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.