Complex Induction of Bovine Uterine Proteins by Interferon-Tau1

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Abstract
Interferon-tau (IFN-τ) is released by the conceptus and induces two uterine proteins during early pregnancy: ubiquitin cross-reactive 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-τ signal transduction in cultured endometrial explants and primary epithelial cells. Recombinant (r) type 1 IFNs (rboIFN-τ and rboIFN-α; 5, 25, 100 nM) induced UCRP, but only rboIFN-τ induced GCP-2 in explant culture. Recombinant boIFN-τ and conceptus secretory proteins containing native IFN-τ induced UCRP and GCP-2 in cultured primary epithelial cells. All concentrations of rboIFN-α (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-τ probably interacts with the janus kinase (Jak)-associated IFN-α receptor to phosphorylate signal transducers and activators of transcription (STAT) and/or interferon regulatory factor-1 (IRF-1). However, IFN-τ-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.