Publications [#180937] of G. Allan Johnson

Papers Published
  1. JY Kim, RC Burghardt, G Wu, GA Johnson, TE Spencer, FW Bazer, Select Nutrients in the Ovine Uterine Lumen. VII. Effects of Arginine, Leucine, Glutamine, and Glucose on Trophectoderm Cell Signaling, Proliferation, and Migration., Biology of reproduction (September, 2010) [doi] .

    Histotroph is required for survival and development of ovine conceptuses (embryo and extra-embryonic membranes). Results from our laboratory indicate that arginine (Arg), leucine (Leu), glutamine (Gln) and glucose increase in the uterine lumen between Days 10 and 15 of pregnancy, coincident with increases in expression of amino acid and glucose transporters by uterine epithelia, as well as trophectoderm and yolk sac of conceptuses, and elongation of the conceptus trophectoderm. Therefore, we hypothesized that Arg, Leu, Gln and glucose have differential effects on hypertrophy, hyperplasia and differentiated functions of trophectoderm cells that are critical to conceptus development. Primary ovine trophectoderm (oTr) cells isolated from Day 15 conceptuses were serum-starved for 24h in a customized medium, deprived of select nutrients and then treated with either Arg, Leu, Gln or glucose. Western blot analyses of whole oTr cell extracts revealed that Arg, Leu and glucose, but not Gln, increased phosphorylated AKT1 (pAKT1) 2.8-, 2.5-, and 1.8-fold, respectively, within 15 min and the increase was maintained to 60 min. Arg, Leu and glucose also stimulated 4.2-, 4.7-, and 2.3-fold increases in phosphorylated RPS6K (pRPS6K) within 15 min, as well as increases in pRPS6 protein between 0 and 30 min post-treatment that were sustained to 60 min. When oTr cells were treated with Arg, pRPS6K protein increased in nuclei, but this was not observed in nuclei of oTr cells treated with Leu and glucose. Immunocytochemical analyses also revealed abundant amounts of phosphorylated RPS6 protein in the cytoplasm of oTr cells treated with Arg, Leu and glucose. Further, Arg and Leu increased proliferation and migration of oTr cells. Collectively, these results indicate that Arg, Leu and glucose, but not Gln, in histotroph coordinately activate AKT1-MTOR and RPS6K-RPS6 cell signaling pathways to stimulate hypertrophy, hyperplasia, and migration of oTr cells.