title: Leucine and arginine regulate trophoblast motility through mTOR-dependent and independent pathways in the preimplantation mouse embryo.
abstract: Uterine implantation is a critical element of mammalian reproduction and is a tightly and highly coordinated event. An intricate and reciprocal uterine-embryo dialog exists to synchronize uterine receptivity with the concomitant activation of the blastocyst, maximizing implantation success. While a number of pathways involved in regulating uterine receptivity have been identified in the mouse, less is understood about blastocyst activation, the process by which the trophectoderm (TE) receives extrinsic cues that initiate new characteristics essential for implantation. Amino acids (AA) have been found to regulate blastocyst activation and TE motility in vitro. In particular, we find that arginine and leucine alone are necessary and sufficient to induce TE motility. Both arginine and leucine act individually and additively to propagate signals that are dependent on the activity of the mammalian target of rapamycin complex 1 (mTORC1). The activities of the well-established downstream targets of mTORC1, p70S6K and 4EBP, do not correlate with trophoblast motility, suggesting that an independent-rapamycin-sensitive pathway operates to induce trophoblast motility, or that other, parallel amino acid-dependent pathways are also involved. We find that endogenous uterine factors act to induce mTORC1 activation and trophoblast motility at a specific time during pregnancy, and that this uterine signal is later than the previously defined signal that induces the attachment reaction. In vivo matured blastocysts exhibit competence to respond to an 8-hour AA stimulus by activating mTOR and subsequently undergoing trophoblast outgrowth by the morning of day 4.5 of pregnancy, but not on day 3.5. By the late afternoon of day 4.5, the embryos no longer require any exposure to AA to undergo trophoblast outgrowth in vitro, demonstrating the existence and timing of an equivalent in vivo signal. These results suggest that there are two separate uterine signals regulating implantation, one that primes the embryo for the attachment reaction and another that activates mTOR and initiates invasive behavior.
authors: Department of Cell Biology, University of Virginia Health System, Charlottesville, VA 22901, USA. img3v@virginia.edu
authors: Isabel M
authors: IM
authors: González
authors: Patrick M
authors: PM
authors: Martin
authors: Carol
authors: C
authors: Burdsal
authors: Jennifer L
authors: JL
authors: Sloan
authors: Sela
authors: S
authors: Mager
authors: Thurl
authors: T
authors: Harris
authors: Ann E
authors: AE
authors: Sutherland
mesh_terms: D026905:Amino Acid Transport Systems / Q000378:metabolism; D000818:Animals; D001120:Arginine / Q000494:pharmacology*; D001692:Biological Transport / Q000187:drug effects; D001755:Blastocyst / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology*; D002465:Cell Movement / Q000187:drug effects*; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D007930:Leucine / Q000494:pharmacology*; D008297:Male; D000076222:Mechanistic Target of Rapamycin Complex 1; D051379:Mice; D008813:Mice, Inbred ICR; D008954:Models, Biological; D046912:Multiprotein Complexes; D010766:Phosphorylation / Q000187:drug effects; D050480:Plasma Membrane Neurotransmitter Transport Proteins / Q000378:metabolism; D014176:Protein Biosynthesis / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D011506:Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D020123:Sirolimus / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*; D013997:Time Factors; D014158:Transcription, Genetic / Q000187:drug effects; D014327:Trophoblasts / Q000166:cytology* / Q000187:drug effects
chemical_list: D026905:Amino Acid Transport Systems; D006063:Chorionic Gonadotropin; D046912:Multiprotein Complexes; D050480:Plasma Membrane Neurotransmitter Transport Proteins; D011506:Proteins; C532353:Slc6A14 protein, mouse; D001120:Arginine; C546843:mTOR protein, mouse; D000076222:Mechanistic Target of Rapamycin Complex 1; D058570:TOR Serine-Threonine Kinases; D007930:Leucine; D020123:Sirolimus