Uterine histotroph and conceptus development. III. Adrenomedullin stimulates proliferation, migration and adhesion of porcine trophectoderm cells via AKT-TSC2-MTOR cell signaling pathway.

Abstract

Adrenomedullin (ADM) as a highly conserved peptide hormone has been reported to increase significantly in the uterine lumen during the peri-implantation period of pregnancy in pigs, but its functional roles in growth and development of porcine conceptus (embryonic/fetus and its extra-embryonic membranes) as well as underlying mechanisms remain largely unknown. Therefore, we conducted in vitro experiments using our established porcine trophectoderm cell line (pTr1) isolated from Day-12 porcine conceptuses to test the hypothesis that porcine ADM stimulates cell proliferation, migration and adhesion via AKT-TSC2-MTOR cell signaling pathway in pTr1 cells. Porcine ADM at 10-7 M stimulated (P<0.05) pTr1 cell proliferation, migration and adhesion by 1.4-, 1.5- and 1.2-folds, respectively. These ADM-induced effects were abrogated (P<0.05) by siRNA-mediated knockdown of ADM (siADM) and its shared receptor component calcitonin-receptor-like receptor (CALCRL; siCALCRL), as well as by rapamycin, the inhibitor of mechanistic target of rapamycin (MTOR). Using siRNA mediated knockdown of CALCRL coupled with Western blot analyses, ADM signaling transduction was determined in which ADM binds to CALCRL to increase phosphorylation of MTOR, its downstream effectors (4EBP1, P70S6K, and S6), and upstream regulators (AKT and TSC2). Collectively, these results suggest that porcine ADM in histotroph act on its receptor component CALCRL to activate AKT-TSC2-MTOR, particularly MTORC1 signaling cascade, leading to elongation,migration and attachment of conceptuses.