Abstract
Sphingosine 1-phosphate (S1P) is a bioactive sphingolipid implicated in diverse cellular functions including survival, proliferation, tumorigenesis, inflammation, and immunity. Sphingosine kinase (SphK) contributes to these functions by converting sphingosine to S1P. We report here that the nonstructural protein NS3 from bovine viral diarrhea virus (BVDV), a close relative of hepatitis C virus (HCV), binds to and inhibits the catalytic activity of SphK1 independently of its serine protease activity, whereas HCV NS3 does not affect SphK1 activity. Uncleaved NS2-3 from BVDV was also found to interact with and inhibit SphK1. We suspect that inhibition of SphK1 activity by BVDV NS3 and NS2-3 may benefit viral replication, because SphK1 inhibition by small interfering RNA, chemical inhibitor, or overexpression of catalytically inactive SphK1 results in enhanced viral replication, although the mechanisms by which SphK1 inhibition leads to enhanced viral replication remain unknown. A role of SphK1 inhibition in viral cytopathogenesis is also suggested as overexpression of SphK1 significantly attenuates the induction of apoptosis in cells infected with cytopathogenic BVDV. These findings suggest that SphK is targeted by this virus to regulate its catalytic activity.
Highlights
bovine viral diarrhea virus (BVDV) encode a single large precursor polyprotein that is processed by cellular and viral proteases into mature structural and nonstructural (NS) proteins
Because free NS3, but not NS2-3, can form an active viral replicase complex with other NS proteins, increased viral RNA synthesis promoted through the release of free NS3 has been suggested to be a determinant of the characteristic lytic phenotype of CP BVDV infections [10]
The significance of the lipid raft as a scaffold for viral replication is further demonstrated by the identification of a novel hepatitis C virus (HCV) replication inhibitor, NA255, which prevents the biosynthesis of sphingolipids, the major components of lipid rafts [13]
Summary
BVDV encode a single large precursor polyprotein that is processed by cellular and viral proteases into mature structural and nonstructural (NS) proteins. To confirm the specific interaction of SphK1 with NS3 and/or NS2-3 expressed in the context of BVDV infection, we transfected an expression vector encoding Flag-SphK following virus infections, immunoprecipitated NS3 and NS2-3 with anti-NS3 mAb, and determined binding to SphK1 by Western blotting.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
