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Published on: September 9, 2014
Zebrafish C-reactive protein isoforms inhibit SVCV replication by blocking autophagy through interactions with cell
Melissa Bello-Perez1, Patricia Pereiro2, Julio Coll3
1Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), Miguel Hernández University (UMH), Elche, 03202, Spain.
Abstract:
In the present work, the mechanisms involved in the recently reported antiviral activity of zebrafish C-reactive protein-like protein (CRP1-7) against the spring viraemia of carp rhabdovirus (SVCV) in fish are explored. The results neither indicate blocking of the attachment or the binding step of the viral replication cycle nor suggest the direct inhibition of G protein fusion activity or the stimulation of the host's interferon system. However, an antiviral state in the host is induced. Further results showed that the antiviral protection conferred by CRP1-7 was mainly due to the inhibition of autophagic processes. Thus, given the high affinity of CRPs for cholesterol and the recently described influence of the cholesterol balance in lipid rafts on autophagy, both methyl-β-cyclodextrin (a cholesterol-complexing agent) and 25-hydroxycholesterol (a cholesterol molecule with antiviral properties) were used to further describe CRP activity. All the tested compounds exerted antiviral activity by affecting autophagy in a similar manner. Further assays indicate that CRP reduces autophagy activity by initially disturbing the cholesterol ratios in the host cellular membranes, which in turn negatively affects the intracellular regulation of reactive oxygen species (ROS) and increases lysosomal pH as a consequence. Ultimately, here we propose that such pH changes exert an inhibitory direct effect on SVCV replication by disrupting the pH-dependent membrane-fusogenic ability of the viral glycoprotein G, which allows the release of the virus from endosomes into cytoplasm during its entry phase.
Insights
Zebrafish CRP1-7 protein inhibits fish rhabdovirus by disrupting cellular autophagy. This antiviral mechanism involves altering cholesterol, reactive oxygen species, and lysosomal pH, ultimately blocking viral entry.
Area of Science:
- Immunology
- Virology
- Cell Biology
Background:
- Zebrafish C-reactive protein-like protein (CRP1-7) exhibits antiviral activity against spring viraemia of carp rhabdovirus (SVCV).
- The precise mechanisms underlying CRP1-7's antiviral effects require elucidation.
Purpose of the Study:
- To investigate the molecular mechanisms of CRP1-7's antiviral activity against SVCV.
- To determine if CRP1-7 interferes with viral attachment, fusion, or host interferon responses.
- To explore the role of autophagy and cholesterol in CRP1-7's antiviral action.
Main Methods:
- Utilized SVCV-infected fish models and cell cultures.
- Assessed viral replication, attachment, and fusion assays.
- Investigated host interferon response and autophagic processes.
- Employed cholesterol-modulating agents like methyl-β-cyclodextrin and 25-hydroxycholesterol.
Main Results:
- CRP1-7 did not block viral attachment or fusion directly, nor did it stimulate the host interferon system.
- Antiviral protection was primarily mediated by the inhibition of host autophagic processes.
- Cholesterol-complexing agents and 25-hydroxycholesterol mimicked CRP1-7's antiviral effects by modulating autophagy.
- CRP1-7 disturbed cellular cholesterol ratios, impacting reactive oxygen species (ROS) and increasing lysosomal pH.
Conclusions:
- CRP1-7 confers antiviral protection against SVCV mainly by inhibiting autophagy.
- The mechanism involves disrupting cellular cholesterol homeostasis, leading to altered ROS levels and increased lysosomal pH.
- Elevated lysosomal pH directly inhibits SVCV replication by affecting the pH-dependent membrane fusion of the viral glycoprotein G.
