Interferon Tau Regulates PGF2α Release from the Ovine Endometrial Epithelial Cells via Activation of Novel JAK/EGFR/ERK/EGR-1 Pathways

In ruminants, pulsatile release of prostaglandin F2α (PGF2α) from the endometrium is transported to the ovary and induces luteolysis thereby allowing new estrous cycle. Interferon tau (IFNT), a type 1 IFN secreted by the trophoblast cells of the developing conceptus, acts on endometrial luminal epithelial (LE) cells and inhibits pulsatile release of PGF2α and establishes pregnancy. One of the unknown mechanisms is that endometrial pulsatile release of PGF2α is inhibited whereas basal release of PGF2α is increased in pregnant compared with nonpregnant sheep. We have recently found that pulsatile release of PGF2α from the endometrium is regulated by prostaglandin transporter (PGT)-mediated mechanisms. We hypothesize that modulation in the endometrial pulsatile vs. basal release of PGF2α likely requires PGT-mediated selective transport, and IFNT interacts with PGT protein and modulates pulsatile vs. basal release of PGF2α. The new findings of the present study are: 1) IFNT activates novel JAK-SRC kinase-EGFR-RAS-RAF-ERK1/2-early growth response (EGR)-1 signaling module in LE cells; 2) IFNT increases interactions between PGT and ERK1/2 or EGR-1 proteins and alters phosphorylation of PGT protein; 3) IFNT precludes action of protein kinase C and Ca2+ on PGT function; and 4) IFNT inhibits 80% PGT-mediated but not 20% simple diffusion-mediated release of PGF2α from the endometrial LE cells through this novel signaling module. The results of the present study provide important new insights on IFNT signaling and molecular control of PGT-mediated release of PGF2α and unravel the underlying mechanisms responsible for the increased basal release of PGF2α at the time of establishment of pregnancy in ruminants.