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Viruses 2018, 10(4), 181;

Baculovirus PTP2 Functions as a Pro-Apoptotic Protein

Laboratory of Virology, Wageningen University & Research, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
Centre for Ecology and Conservation, Biosciences, University of Exeter, Penryn, Cornwall TR10 9FE, UK
Author to whom correspondence should be addressed.
Received: 13 February 2018 / Revised: 16 March 2018 / Accepted: 5 April 2018 / Published: 7 April 2018
(This article belongs to the Special Issue Antiviral Defense in Invertebrates)
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The family Baculoviridae encompasses a large number of invertebrate viruses, mainly infecting caterpillars of the order Lepidoptera. The baculovirus Spodoptera exigua multiple nucleopolyhedrovirus (SeMNPV) induces physiological and behavioral changes in its host Spodoptera exigua, as well as immunological responses, which may affect virus transmission. Here we show that the SeMNPV-encoded protein tyrosine phosphatase 2 (PTP2) induces mild apoptosis in Spodoptera frugiperda (Sf) 21 cells upon transient expression. Transient expression of a catalytic-site mutant of ptp2 did not lead to apoptosis, indicating that the phosphatase activity of PTP2 is needed to induce apoptosis. We also found that the caspase level (indicator of apoptosis) was higher in cells transfected with the ptp2 gene than in cells transfected with the catalytic mutant. Adding a caspase inhibitor reduced the level of ptp2-induced apoptosis. Moreover, deletion of the ptp2 gene from the viral genome prevented the induction of apoptosis in S. exigua hemocytes. The virus titer and virulence indices (the viral infectivity and the time to death) were not affected by deletion of the ptp2 gene. However, the viral occlusion body yield from S. exigua larvae infected with the mutant virus lacking the ptp2 gene was much lower than the yield from larvae infected with the wild-type (WT) virus. We hypothesize that the observed pro-apoptotic effects of PTP2 are the result of PTP2-mediated immune suppression in larvae, which consequently leads to higher viral occlusion body yields. View Full-Text
Keywords: baculovirus; apoptosis; Spodoptera exigua; SeMNPV; protein tyrosine phosphatase 2; pro-apoptotic effects; caspase assay; hemocytes; Lepidoptera baculovirus; apoptosis; Spodoptera exigua; SeMNPV; protein tyrosine phosphatase 2; pro-apoptotic effects; caspase assay; hemocytes; Lepidoptera

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Han, Y.; van Houte, S.; van Oers, M.M.; Ros, V.I. Baculovirus PTP2 Functions as a Pro-Apoptotic Protein. Viruses 2018, 10, 181.

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