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Impaired protein kinase C activation/translocation in Epstein-Barr virus-infected monocytes
Melanie Tardif1, Martin Savard, Louis Flamand
1Laboratory of Viral Immunology, Laboratory of Virology, Centre de Recherche en Rhumatologie et Immunologie, Centre de Recherche du Centre Hospitalier de l'Université Laval, and Université Laval, Québec G1V 4G2, Canada.
Abstract:
Infection of human monocytes by Epstein-Barr virus (EBV) has been linked to a decrease in the production of proinflammatory mediators as well as an impairment of phagocytosis. Considering the key role of protein kinases C (PKCs) in many biological functions of monocytes, including phagocytosis, we investigated the effects of EBV on the PKC activity in infected monocytes. Our results indicate that infection of monocytes by EBV impairs both phorbol 12-myristate 13-acetate (PMA)-induced translocation of PKC isozymes alpha and beta from cytosol to membrane as well as the PKC enzymatic activity. Similarly, the subcellular distribution of the receptor for activated C kinase (RACK), an anchoring protein essential to PKC translocation, was also found to be reduced in EBV-infected monocytes. Transfection of 293T cells with an expression vector coding for the immediate-early protein ZEBRA of EBV resulted in impaired PMA-induced translocation and activity of PKC. Using co-immunoprecipitation assays, the ZEBRA protein was found to physically interact with the RACK1 protein. Thus interaction of ZEBRA with RACK likely results in the inhibition of PKC activity, which in turn affects functions of monocytes, such as phagocytosis.
Insights
Epstein-Barr virus (EBV) infection impairs protein kinase C (PKC) activity in monocytes by affecting PKC translocation and enzymatic function. This inhibition, mediated by the ZEBRA protein interacting with RACK1, impacts monocyte functions like phagocytosis.
Area of Science:
- Immunology
- Virology
- Cell Biology
Background:
- Epstein-Barr virus (EBV) infection in human monocytes is associated with reduced proinflammatory mediators and impaired phagocytosis.
- Protein kinases C (PKCs) are crucial for monocyte functions, including phagocytosis.
Purpose of the Study:
- To investigate the impact of EBV infection on protein kinase C (PKC) activity within infected human monocytes.
- To elucidate the molecular mechanisms by which EBV affects PKC signaling pathways.
Main Methods:
- Assessing phorbol 12-myristate 13-acetate (PMA)-induced translocation and enzymatic activity of PKC isozymes alpha and beta in EBV-infected monocytes.
- Analyzing the subcellular distribution of the receptor for activated C kinase (RACK) in EBV-infected monocytes.
- Transfecting 293T cells with EBV's ZEBRA protein and evaluating its effect on PMA-induced PKC activity.
- Employing co-immunoprecipitation assays to detect physical interactions between ZEBRA and RACK1 proteins.
Main Results:
- EBV infection significantly impairs PMA-induced translocation of PKC isozymes alpha and beta and reduces overall PKC enzymatic activity.
- The subcellular distribution of RACK, a key anchoring protein for PKC, is diminished in EBV-infected monocytes.
- Expression of EBV's ZEBRA protein in 293T cells mimicked the effects of EBV infection, inhibiting PKC translocation and activity.
- Co-immunoprecipitation confirmed a physical interaction between the EBV ZEBRA protein and the RACK1 protein.
Conclusions:
- EBV infection disrupts monocyte function by inhibiting PKC activity, a process likely mediated by the ZEBRA protein.
- The interaction between ZEBRA and RACK1 is a key mechanism by which EBV impairs PKC signaling and consequently affects monocyte functions such as phagocytosis.