L-Proline Activates Mammalian Target of Rapamycin Complex 1 and Modulates Redox Environment in Porcine Trophectoderm Cells

Abstract

L-proline (proline) is a key regulator of embryogenesis, placental development, and fetal growth. However, the underlying mechanisms that support the beneficial effects of proline are largely unknown. This study used porcine trophectoderm cell line 2 (pTr2) to investigate the underlying mechanisms of proline in cell proliferation and redox homeostasis. Cells were cultured in the presence of 0, 0.25, 0.50, or 1.0 mmol/L proline for an indicated time. The results showed that 0.5 and 1.0 mmol/L proline enhanced cell viability. These effects of proline (0.5 mmol/L) were accompanied by the enhanced protein abundance of p-mTORC1, p-p70S6K, p-S6, and p-4E-BP1. Additionally, proline dose-dependently enhanced the mRNA expression of proline transporters [solute carrier family (<i>SLC</i>) <i>6A20</i>, <i>SLC36A1</i>, <i>SLC36A2</i>, <i>SLC38A1</i>, and <i>SLC38A2</i>], elevated proline concentration, and protein abundance of proline dehydrogenase (PRODH). Furthermore, proline addition (0.25 or 0.5 mmol/L) resulted in lower abundance of p-AMPK<i>α</i> when compared with a control. Of note, proline resulted in lower reactive oxygen species (ROS) level, upregulated mRNA expression of the catalytic subunit of glutamate-cysteine ligase (<i>GCLC</i>) and glutathione synthetase (<i>GSS</i>), as well as enhanced total (T)-GSH and GSH concentration when compared with a control. These data indicated that proline activates themTORC1 signaling and modulates the intracellular redox environment via enhancing proline transport.