title: ATF3 expression in the corpus luteum: possible role in luteal regression.
abstract: The present study investigated the induction and possible role of activating transcription factor 3 (ATF3) in the corpus luteum. Postpubertal cattle were treated at midcycle with prostaglandin F2α(PGF) for 0-4 hours. Luteal tissue was processed for immunohistochemistry, in situ hybridization, and isolation of protein and RNA. Ovaries were also collected from midluteal phase and first-trimester pregnant cows. Luteal cells were prepared and sorted by centrifugal elutriation to obtain purified small (SLCs) and large luteal cells (LLCs). Real-time PCR and in situ hybridization showed that ATF3 mRNA increased within 1 hour of PGF treatment in vivo. Western blot and immunohistochemistry demonstrated that ATF3 protein was expressed in the nuclei of LLC within 1 hour and was maintained for at least 4 hours. PGF treatment in vitro increased ATF3 expression only in LLC, whereas TNF induced ATF3 in both SLCs and LLCs. PGF stimulated concentration- and time-dependent increases in ATF3 and phosphorylation of MAPKs in LLCs. Combinations of MAPK inhibitors suppressed ATF3 expression in LLCs. Adenoviral-mediated expression of ATF3 inhibited LH-stimulated cAMP response element reporter luciferase activity and progesterone production in LLCs and SLCs but did not alter cell viability or change the expression or activity of key regulators of progesterone synthesis. In conclusion, the action of PGF in LLCs is associated with the rapid activation of stress-activated protein kinases and the induction of ATF3, which may contribute to the reduction in steroid synthesis during luteal regression. ATF3 appears to affect gonadotropin-stimulated progesterone secretion at a step or steps downstream of PKA signaling and before cholesterol conversion to progesterone.
authors.affiliation: Olson Center for Women's Health, Department of Obstetrics/Gynecology, Nebraska Medical Center, Omaha, NE 68198. jsdavis@unmc.edu.
authors.forename: Dagan
authors.initials: D
authors.lastname: Mao
authors.forename: Xiaoying
authors.initials: X
authors.lastname: Hou
authors.forename: Heather
authors.initials: H
authors.lastname: Talbott
authors.forename: Robert
authors.initials: R
authors.lastname: Cushman
authors.forename: Andrea
authors.initials: A
authors.lastname: Cupp
authors.forename: John S
authors.initials: JS
authors.lastname: Davis
mesh_terms: D051700:Activating Transcription Factor 3 / Q000235:genetics* / Q000378:metabolism; D000256:Adenoviridae / Q000378:metabolism; D000818:Animals; D002417:Cattle; D002470:Cell Survival / Q000187:drug effects; D003338:Corpus Luteum / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D015237:Dinoprost / Q000494:pharmacology; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D006888:Hydroxycholesterols / Q000494:pharmacology; D007986:Luteinizing Hormone / Q000494:pharmacology; D003341:Luteolysis / Q000187:drug effects / Q000235:genetics*; D020935:MAP Kinase Signaling System / Q000187:drug effects; D010766:Phosphorylation / Q000187:drug effects; D011374:Progesterone / Q000096:biosynthesis / Q000494:pharmacology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020218:Response Elements / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D013997:Time Factors; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D051700:Activating Transcription Factor 3; D006888:Hydroxycholesterols; D047428:Protein Kinase Inhibitors; D012333:RNA, Messenger; C003585:22-hydroxycholesterol; D011374:Progesterone; D007986:Luteinizing Hormone; D015237:Dinoprost; D017868:Cyclic AMP-Dependent Protein Kinases