PTP-H2 and PTP-H3 from Microplitis demolitor Bracovirus Localize to Focal Adhesions and Are Antiphagocytic in Insect Immune Cells

Abstract

Viruses in the family Polydnaviridae are symbiotically associated with parasitoid wasps. Wasps inject polydnaviruses (PDVs) when laying an egg into their insect host, and expression of viral gene products causes several physiological alterations, including immunosuppression, that allow the wasp's progeny to develop. As with other PDVs, most Microplitis demolitor bracovirus (MdBV) genes are related variants that form gene families. The largest MdBV gene family includes 13 members that encode predicted proteins related to protein tyrosine phosphatases (PTPs). Sequence analysis during the present study indicated that five PTP family members (PTP-H2, -H3, -N1, and -N2) have fully conserved catalytic domains, whereas other family members exhibited replacements, deletions, or rearrangements of amino acids considered essential for tyrosine phosphatase activity. Expression studies indicated that most MdBV PTP genes are expressed in virus-infected host insects, with transcript abundance usually being highest in hemocytes. MdBV-infected hemocytes also exhibited higher levels of tyrosine phosphatase activity than noninfected hemocytes. We produced expression constructs for four of the most abundantly expressed PTP family members and conducted functional studies with hemocyte-like Drosophila S2 cells. These experiments suggested that recombinant PTP-H2 and PTP-H3 are functional tyrosine phosphatases whereas PTP-H1 and PTP-J1 are not. PTP-H2 and -H3 localized to focal adhesions in S2 cells, and coexpression with another MdBV gene product, Glc1.8, resulted in complete inhibition of phagocytosis.

Infection by a symbiotic polydnavirus induces wasting and inhibits metamorphosis of the mothPseudoplusia includens

“…The first is that post-critical weight larvae are refractory to infection or that insufficient time exists after infection of post-critical weight larvae for the effects of viral expression to block pupation. We think this unlikely given prior analyses of the fully sequenced MdBV genome which indicate transcription of most viral genes begins within 2 h of infection and continues near steady state for multiple days thereafter with no differences between last instar hosts infected pre-and post-critical weight (Strand et al, 1992;Strand, 1994;Webb et al, 2006;Pruijssers and Strand, 2007; (and M.R.S. and M. H. Beck, unpublished).…”

Ovary ecdysteroidogenic hormone requires a receptor tyrosine kinase to activate egg formation in the mosquito Aedes aegypti

“…All experiments were conducted using the UGAL strain of A. aegypti, which was reared as described (9). S2 cells from D. melanogaster were maintained at 27°C in serum-free SFX medium (HyClone) (36). Recombinant A. aegypti OEH (18,278 Da) was produced and purified as described (8,9).…”

“…AAEL001915 cloned in frame with the V5-6xHis epitope tag was confirmed by sequencing. This plasmid was then transfected into S2 cells followed by Zeocin selection as previously described (36,42).…”

Tissue specificity of a baculovirus-expressed, basement membrane-degrading protease in larvae of Heliothis virescens

“…This infection also results in a more global suppression of the cellular immune response, because hemocytes are also unable to phagocytize bacteria or to encapsulate other foreign targets (Beck and Strand, 2003;Beck and Strand, 2005;Pruijssers and Strand, 2007).…”