Negative regulation of prophenoloxidase (proPO) activation by a clip-domain serine proteinase homolog (SPH) from endoparasitoid venom

Zhang, Guangmei; Lu, Zhiqiang; Jiang, Haobo; Asgari, Sassan

doi:10.1016/j.ibmb.2004.02.009

Cited by 88 publications

(66 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…function. Virulence proteins include serine proteinase homolog (24,49) and unrelated peptide Vn 4.6 (22) from Cotesia rubecula venom, extracellular superoxide dismutase (25) and serpin (23) from Leptopilina boulardi venom, and epidermal growth factor-like proteins (26,48,52) from Microplitis demolitor PDV. With an estimated 600,000 species, parasitoid wasps are one of the most abundant and diverse insect groups on earth (53).…”

Section: Discussionmentioning

confidence: 99%

A Venom Serpin Splicing Isoform of the Endoparasitoid Wasp Pteromalus puparum Suppresses Host Prophenoloxidase Cascade by Forming Complexes with Host Hemolymph Proteinases

Yan

Fang

Liu

et al. 2017

Journal of Biological Chemistry

View full text Add to dashboard Cite

Edited by Charles E. SamuelTo ensure successful parasitism, parasitoid wasps inject venom along with their eggs into their hosts. The venom serves to suppress host immune responses, including melanization. Venom from Pteromalus puparum, a pupal endoparasitoid, inhibits melanization of host hemolymph in vitro in a dose-dependent manner. Using assay-guided fractionation, a serpin splicing isoform with phenoloxidase inhibitory activity was identified as P. puparum serpin-1, venom isoform (PpS1V). This serpin gene has 16 predicted splicing isoforms that differ only in the C-terminal region. RT-PCR results show that the specific serpin isoform is differentially expressed in the venom gland. Recombinant PpS1V (rPpS1V) suppresses host prophenoloxidase (PPO) activation rather than inhibiting the phenoloxidase directly. Pulldown assays show that PpS1V forms complexes with two host hemolymph proteins, here named Pieris rapae hemolymph proteinase 8 (PrHP8) and P. rapae prophenoloxidase-activating proteinase 1 (PrPAP1), based on gene sequence blasting and phylogenetic analysis. The role of rPrPAP1 in the PPO activation cascade and its interaction with rPpS1V were confirmed. The stoichiometry of inhibition of PrPAP1 by PpS1V is 2.3. PpS1V also inhibits PPO activation in a non-natural host, Ostrinia furnacalis, through forming a complex with O. furnacalis serine protease 13 (OfSP13), an ortholog to PrPAP1. Our results identify a venom-enriched serpin isoform in P. puparum that inhibits host PPO activation, probably by forming a complex with host hemolymph proteinase PrPAP1.

show abstract

Section: Discussionmentioning

confidence: 99%

A Venom Serpin Splicing Isoform of the Endoparasitoid Wasp Pteromalus puparum Suppresses Host Prophenoloxidase Cascade by Forming Complexes with Host Hemolymph Proteinases

Yan

Fang

Liu

et al. 2017

Journal of Biological Chemistry

View full text Add to dashboard Cite

show abstract

“…Thus, the possible target enzyme(s) and function of Egf0.4 in parasitism remains unknown. Although several insect pathogens, including multiple polydnaviruses, inhibit the melanization response of their hosts (18,21,38,39), little is known about the virulence factors responsible or their mode of action. To our knowledge Egf1.0 provides the first example for how a specific, pathogen-encoded gene product suppresses the PO cascade.…”

Section: Egf1mentioning

confidence: 99%

The Viral Protein Egf1.0 Is a Dual Activity Inhibitor of Prophenoloxidase-activating Proteinases 1 and 3 from Manduca sexta

Beck

Wang

et al. 2008

Journal of Biological Chemistry

Self Cite

View full text Add to dashboard Cite

Some pathogens are capable of suppressing the melanization response of host insects, but the virulence factors responsible are largely unknown. The insect pathogen Microplitis demolitor bracovirus encodes the Egf family of small serine proteinase inhibitors. One family member, Egf1.0, was recently shown to suppress melanization of hemolymph in Manduca sexta in part by inhibiting the enzymatic activity of prophenoloxidase activating proteinase 3 (PAP3). However, other experiments suggested this viral protein suppresses melanization by more than one mechanism. Here we report that Egf1.0 inhibited the amidolytic activity of PAP1 and dose-dependently blocked processing of pro-PAP1 and pro-PAP3. Consistent with its PAP inhibitory activity, Egf1.0 also prevented processing of pro-phenoloxidase, serine proteinase homolog (SPH) 1, and SPH2. Isolation of Egf1.0-protein complexes from plasma indicated that Egf1.0 binds PAPs through its C-terminal repeat domain. Egf1.0 also potentially interacts with SPH2 and two other proteins, ferritin and gloverin, not previously associated with the phenoloxidase cascade. Overall, our results indicate that Egf1.0 is a dual activity PAP inhibitor that strongly suppresses the insect melanization response.Melanization of hemolymph is a conserved humoral immune response that is elicited in most if not all arthropods by wounding and infection. Regulation of the melanization response is controlled by one or more cascades comprised of phenoloxidases (POs) 2 and other, mostly unknown, serine proteinases (1, 2). Biochemical studies in the lepidopteran Manduca sexta have identified one initiation serine proteinase (hemolymph protein 14 (HP14)) that autoactivates in the presence of microbial elicitors (3, 4), a downstream proteinase (HP21) activated by HP14, and three terminal PAPs (PAP1, 2, 3) that cleave pro-PO at its Arg-Phe reactive site bond to form PO. Activated PO then catalyzes the formation of reactive intermediates and melanin that accumulate around pathogens, encapsulated parasites, and wound sites (4 -8). HP21 was recently shown to process pro-PAP2 and pro-PAP3 (9, 10). Full activation of PO by PAPs in M. sexta also requires processing of catalytically inactive SPH precursors (8, 11), whereas negative regulation of the PO cascade involves at least four serpins that inhibit HP21, PAPs, or other HPs (2). Biochemical studies in the silkmoth Bombyx mori and beetle Holotrichia diomphalia have identified other PAPs (named PPAF (pro-phenoloxidase activating factor) and PPAE (pro-phenoloxidase activating enzyme)) (12, 13), whereas genetic screens in Drosophila melanogaster and the mosquito Anopheles gambiae have identified additional serine proteinases with mostly unknown functions in the melanization process (14 -17).Several pathogens and parasites of insects have evolved counterstrategies for suppressing melanization and other host immune defenses (18 -20). Relatively little is known, however, about the virulence factors responsible or the host molecules with which they interact. Thousands o...

show abstract

“…In contrast, Egf genes have not been identified in PDVs from other wasp genera, indicating that they or their associated parasitoids have evolved other means for disrupting the host melanization response. One example is the identification of an SPH in the venom of a PDV-carrying wasp in the genus Cotesia that disrupts melanization by an unknown mechanism (44). Other anti-melanization strategies are also possible, as recently illustrated by an insect pathogenic bacterium (45).…”

mentioning

confidence: 99%

A novel polydnavirus protein inhibits the insect prophenoloxidase activation pathway

Beck

Strand

2007

Proc. Natl. Acad. Sci. U.S.A.

132

140

View full text Add to dashboard Cite

Pathogens often suppress the melanization response of host insects, but the underlying molecular mechanisms are largely unknown. Here we report that Microplitis demolitor bracovirus (MdBV) carried by the wasp M. demolitor produces a protein, Egf1.0, which inhibits the phenoloxidase (PO) cascade. Egf1.0 belongs to a larger gene family that shares a cysteine-rich motif with similarities to the trypsin inhibitor-like (TIL) domains of small serine proteinase inhibitors (smapins). Gain-of-function and RNAi experiments indicated that the Egf genes are the only MdBVencoded factors responsible for disabling the insect melanization response. Known smapins bind target proteinases in a substratelike fashion and are cleaved at a single reactive site bond. The P1-P1 position for Egf1.0 has the sequence Arg-Phe, which suggested that its target proteinase is a prophenoloxidase-activating proteinase (PAP). Wild-type Egf1.0 inhibited PAP-3 from Manduca sexta, whereas Egf1.0 R51A , whose reactive-site arginine was replaced with an alanine, had no PAP-3 inhibitory activity. Other experiments using wild-type and mutant constructs indicated that Egf1.0 blocks activation of the PO cascade via PAP inhibition. Overall, our results identify a novel inhibitor of the PO cascade and indicate that suppression of the host melanization response is functionally important for both the virus and its associated wasp. melanization ͉ virulence ͉ immunity ͉ parasite ͉ antiviral

show abstract

Negative regulation of prophenoloxidase (proPO) activation by a clip-domain serine proteinase homolog (SPH) from endoparasitoid venom

Cited by 88 publications

References 27 publications

A Venom Serpin Splicing Isoform of the Endoparasitoid Wasp Pteromalus puparum Suppresses Host Prophenoloxidase Cascade by Forming Complexes with Host Hemolymph Proteinases

A Venom Serpin Splicing Isoform of the Endoparasitoid Wasp Pteromalus puparum Suppresses Host Prophenoloxidase Cascade by Forming Complexes with Host Hemolymph Proteinases

The Viral Protein Egf1.0 Is a Dual Activity Inhibitor of Prophenoloxidase-activating Proteinases 1 and 3 from Manduca sexta

A novel polydnavirus protein inhibits the insect prophenoloxidase activation pathway

Contact Info

Product

Resources

About