Complex Induction of Bovine Uterine Proteins by Interferon-Tau

Interferon-tau (IFN-(tau)) is released by the conceptus and induces two uterine proteins during early pregnancy: ubiquitin crossreactive protein (UCRP) and granulocyte chemotactic protein-2 (GCP-2). The present experiments were designed to determine whether detection (Western blot) of cytosolic UCRP and release of GCP-2 could be used to examine IFN-(tau) signal transduction in cultured endometrial explants and primary epithelial cells. Recombinant (r) type 1 IFNs (rboIFN-(tau) and rboIFN-(alpha); 5, 25, 100 nM) induced UCRP, but only rboIFN-(tau) induced GCP-2 in explant culture. Recombinant boIFN-(tau) and conceptus secretory proteins containing native IFN-(tau) induced UCRP and GCP-2 in cultured primary epithelial cells. All concentrations of rboIFN-(alpha) (25, 50, 100 nM) induced UCRP, but only the highest concentration induced GCP-2 in cultured primary epithelial cells. Interestingly, phorbol ester (100, 500, 1000 ng/ml) induced GCP-2, but it had no effect on UCRP. Because type 1 IFNs induce UCRP, IFN-(tau) probably interacts with the janus kinase (Jak)-associated IFN-(alpha) receptor to phosphorylate signal transducers and activators of transcription (STAT) and/or interferon regulatory factor-1 (IRF-1). However, IFN-(tau)-specific induction of GCP-2 may involve a variant type 1 receptor subunit or activators of transcription that are associated with protein kinase C and the Jak/STAT/IRF-1 pathway.