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PubMed1997

Envelope protein of parasitic wasp symbiont virus, polydnavirus, protects the wasp eggs from cellular immune reactions by the host insect.

Cotesia kariyai polydnavirus (CkPDV) virions are present in the oviducts of C. kariyai wasp and are injected with eggs into the hemocoel of the host armyworm Pseudaletia separata larvae during parasitization. Evidence that the presence of polydnavirus particles on the surface of the wasp eggs may be essential for prevention of cellular immune reactions by the host hemocytes was obtained by isolating an immunoevasive factor from CkPDV virions. The purified proteinaceous factor protects foreign materials from adhesion and encapsulation by hemocytes of the host P. separata larvae but not by those of common cutworm Spodoptera litura larvae which is an incompatible host for the C. kariyai wasp. Purification procedures consisted of extraction with ethanol/trifluoroacetic acid and reverse-phase high performance liquid chromatography. A factor with a molecular mass of approximately 50 kDa is demonstrated to be present on the envelope of CkPDV virion by immunoelectronmicroscopic observations. Furthermore, immunoreactive proteins are found in plasma of the armyworm larvae but not in the common cutworm larvae, indicating that only the natural host of C. kariyai wasp shares a similar epitope with CkPDV. The sequence of 23 amino acid residues at the amino terminus of the factor was determined to be Ile-Ser-Val-Glu-Asn-Val-Xaa-Thr-Thr-Gly-Ile-Phe-Leu-Asp-Ser-Gly-Glu-Xaa- Val- Pro-Tyr-Ala-Thr-Lys-Pro.

Animals↗
PubMed2007

Multiple WASP-interacting protein recognition motifs are required for a functional interaction with N-WASP.

The WASP-interacting protein (WIP) targets WASP/WAVE proteins through a constitutive interaction with an amino-terminal enabled/VASP homology (EVH1) domain. Parallel investigations had previously identified two distinct N-WASP binding motifs corresponding to WIP residues 451-461 and 461-485, and we determined the structure of a complex between WIP-(461-485) and the N-WASP EVH1 domain (Volkman, B. F., Prehoda, K. E., Scott, J. A., Peterson, F. C., and Lim, W. A. (2002) Cell 111, 565-576). The present results show that, when combined, the WIP-(451-485) sequence wraps further around the EVH1 domain, extending the interface observed previously. Specific contacts with three WIP epitopes corresponded to regions of high sequence conservation in the verprolin family. A central polyproline motif occupied the canonical binding site but in a reversed orientation relative to other EVH1 complexes. This interaction was augmented in the amino- and carboxyl-terminal directions by additional hydrophobic contacts involving WIP residues 454-459 and 475-478, respectively. Disruption of any of the three WIP epitopes reduced N-WASP binding in cells, demonstrating a functional requirement for the entire binding domain, which is significantly longer than the polyproline motifs recognized by other EVH1 domains.

Amino Acid Motifs↗
PubMed2003

Cryptic species of fig-pollinating wasps: implications for the evolution of the fig-wasp mutualism, sex allocation, and precision of adaptation.

Fig-pollinating wasps have provided model systems for developing and testing theories of the evolution of mutualism, sex allocation, and precision of adaptation. With few exceptions, previous studies have assumed one species of pollinator wasp per host fig species. Here we report genetic data demonstrating the coexistence of previously undetected cryptic fig wasp species in at least half of the host fig species surveyed. The substantial mitochondrial sequence differences (4.2-6.1%) imply old divergences ( approximately 1.5-5.1 million years ago) among these species. Furthermore, some cryptic species pairs seem to be sister taxa, whereas others clearly are not, indicating both long-term coexistence on shared hosts and the colonization of novel fig species. These findings undermine the prevalent notion of strict one-to-one specificity between cospeciating figs and their pollinators, thereby challenging existing theory concerning the evolution and stability of mutualisms. Moreover, the incorporation of the genetic information significantly improves the fit of the observed sex ratios to predictions of local mate-competition theory, further strengthening support for sex allocation theory and the precision of adaptation.

Animals↗
PubMed2000

Double sensitization to honeybee and wasp venom: immunotherapy with one or with both venoms? Value of FEIA inhibition for the identification of the cross-reacting ige antibodies in double-sensitized patients to honeybee and wasp venom.

BACKGROUND: Double sensitization to honeybee (Apis mellifera) and wasp venom (Vespula spp.) as determined by skin test and measurement of specific IgE is common in hymenoptera sting allergy. Double-sensitized patients have either distinct antibodies for each venom or cross-reacting antibodies that recognize similar or identical epitopes in both venoms. Unfortunately, patients often fail to identify the stinging insect which makes it difficult to distinguish cross-reactors from non cross-reactors. However, for economic reasons as well as for the benefit of the patients, it would be useful to identify complete cross-reactors. METHODS: In this study we investigated 24 double-sensitized patients who were candidates for venom immunotherapy. Homologous and heterologous FEIA inhibition was carried out with honeybee (Apis mellifera) and wasp venom (Vespula spp.) preparations from two different providers. The inhibitor concentrations were ranging from 0 to 100 microg protein/ml. RESULTS: Sera of 4 patients were completely cross-reacting for one venom (3 honeybee, 1 wasp), 8 patients were partially cross-reacting and 10 patients were not cross-reacting. Two patients were excluded from the study due to insufficient homologous inhibition. Data from specific IgE measurements, skin test, and clinical history were not useful for the identification of cross-reacting patients. CONCLUSION: FEIA inhibition is easy to perform and useful for the identification of patients with complete cross-reactivity. In these patients immunotherapy might be restricted to one venom which is beneficial for the patient and cost-effective.

Adolescent↗
PubMed2002

Identification of novel SH3 domain ligands for the Src family kinase Hck. Wiskott-Aldrich syndrome protein (WASP), WASP-interacting protein (WIP), and ELMO1.

The importance of the SH3 domain of Hck in kinase regulation, substrate phosphorylation, and ligand binding has been established. However, few in vivo ligands are known for the SH3 domain of Hck. In this study, we used mass spectrometry to identify approximately 25 potential binding partners for the SH3 domain of Hck from the monocyte cell line U937. Two major interacting proteins were the actin binding proteins Wiskott-Aldrich syndrome protein (WASP) and WASP-interacting protein (WIP). We also focused on a novel interaction between Hck and ELMO1, an 84-kDa protein that was recently identified as the mammalian ortholog of the Caenorhabditis elegans gene, ced-12. In mammalian cells, ELMO1 interacts with Dock180 as a component of the CrkII/Dock180/Rac pathway responsible for phagocytosis and cell migration. Using purified proteins, we confirmed that WASP-interacting protein and ELMO1 interact directly with the SH3 domain of Hck. We also show that Hck and ELMO1 interact in intact cells and that ELMO1 is heavily tyrosine-phosphorylated in cells that co-express Hck, suggesting that it is a substrate of Hck. The binding of ELMO1 to Hck is specifically dependent on the interaction of a polyproline motif with the SH3 domain of Hck. Our results suggest that these proteins may be novel activators/effectors of Hck.

Adaptor Proteins, Signal Transducing↗
PubMed1985

Wasp venom peptides; wasp kinins, new cytotrophic peptide families and their physico-chemical properties.

In addition to wasp kinins, the wasp venom contains a series of hydrophobic peptides, mastoparans and chemotactic peptides as major peptidergic components. The first major component in the venom is mastoparam. The peptides in the mastoparan family are tetradecapeptide amides which cause degranulation of the mast cells to release histamine from the cells, and act on the adrenal chromaffin cells to release catecholamines and adenylic acids. Some mastoparans cause hemolysis and serotonin release from the platelets. The new cytotrophic peptides as the second major components are tridecapeptide amides possessing chemotactic activity for polymorphonuclear leucocytes and monocytes. Some of the peptides in this family also cause histamine release from the mast cells. Mastoparan takes a random coil structure in aqueous solution but changes its conformation to alpha-helix in methanolic solution or in the presence of lysophosphatidyl choline. This fact is confirmed also by the transferred nuclear overhauser effect by NMR analysis. The similar phenomenon was observed in the family of chemotactic peptides. The helical conformation of these peptides are amphipathic structure in which all of side chains of the hydrophobic amino acids are located on one side of the axis, and those of the basic or the hydrophilic amino acid residues are on an opposite side. Mastoparan enhances the membrane conductivity of the lipid bilayer when the peptide is investigated by the black lipid membrane experiment. This indicates that the peptide may be assembled in the membrane by changing its conformation and, for some reason, enhances the ion transfer through the membrane. These properties of the peptide may reveal various activities on the cell membrane.

Animals↗
PubMed1996

Polydnavirus DNA of the braconid wasp Chelonus inanitus is integrated in the wasp's genome and excised only in later pupal and adult stages of the female.

Many endoparasitic wasps inject, along with the egg, polydnavirus into their insect hosts, the virus being a prerequisite for successful parasitoid development. The genome of polydnaviruses consists of multiple circular dsDNA molecules of variable size. We show for a 12 kbp segment of the braconid Chelonus inanitus (CiV12) that it is integrated into the wasp genome. This is the first direct demonstration of integration for a bracovirus. PCR data indicated that the integrated form of CiV12 was present in all male and female stages investigated while the excised circular virus DNA only appeared in females after a specific stage in pupal-adult development. The data also indicated that after excision of virus DNA the genomic DNA was rejoined. This has not yet been reported for any polydnavirus. Sequence analyses in the junction regions revealed the presence of an imperfect consensus sequence of 15 nucleotides in CiV12, in each terminus of the integrated virus DNA and in the rejoined genomic DNA. Within these repeats two sequence types (ATA, TAC) were observed in the various virus clones and in the clones encompassing the rejoined genomic DNA; they corresponded to the sequence type in the right and left junction, respectively. To explain this, we propose a model of virus DNA replication in which the genomic DNA is folded to juxtapose the direct repeat of the left with that of the right junction; recombination at specific sites would then yield the two types of virus and rejoined genomic DNA.

Animals↗
PubMed1977

Bee and wasp stings of the eye. Retained intralenticular wasp sting: A case report.

Two different stages should be considered in the management of bee and wasp stings to the eye. The first is the acute stage of activity of the specific insect venom on the structures the eye. The reaction of the eye to the particular insult is considered here in regard to the anterior and posterior segments of the eye. The second stage is that of the retained intraocular foreign body, the inert sting. Little is known about the reaction of the eye to the presence of chitinous sting and its effect on the structures of the eye. We report a follow-up study of a sting retained for 28 years, and emphasise the benign and quiescent course of the case. Guidelines for treatment and management in such cases are described.

Bees↗
PubMed2005

Interaction of HSP90 to N-WASP leads to activation and protection from proteasome-dependent degradation.

Neural Wiskott-Aldrich syndrome protein (N-WASP) regulates reorganization of the actin cytoskeleton through activation of the Arp2/3 complex. Here, we show that heat shock protein 90 (HSP90) regulates N-WASP-induced actin polymerization in cooperation with phosphorylation of N-WASP. HSP90 binds directly to N-WASP, but binding alone does not affect the rate of N-WASP/Arp2/3 complex-induced in vitro actin polymerization. An Src family tyrosine kinase, v-Src, phosphorylates and activates N-WASP. HSP90 increases the phosphorylation of N-WASP by v-Src, leading to enhanced N-WASP-dependent actin polymerization. In addition, HSP90 protects phosphorylated and activated N-WASP from proteasome-dependent degradation, resulting in amplification of N-WASP-dependent actin polymerization. Association between HSP90 and N-WASP is increased in proportion to activation of N-WASP by phosphorylation. HSP90 is colocalized and associated with active N-WASP at podosomes in 3Y1/v-Src cells and at growing neurites in PC12 cells, whose actin structures are clearly inhibited by blocking the binding of HSP90 to N-WASP. These findings suggest that HSP90 induces efficient activation of N-WASP downstream of phosphorylation signal by Src family kinases and is critical for N-WASP-dependent podosome formation and neurite extension.

Actin-Related Protein 2↗
PubMed2003

Translocation of N-WASP by nuclear localization and export signals into the nucleus modulates expression of HSP90.

N-WASP regulates the actin cytoskeleton through activation of the Arp2/3 complex. N-WASP localizes at the cell periphery, where it controls actin polymerization downstream of signal molecules such as adapter proteins, Cdc42, Src family kinases, and phosphoinositides. N-WASP also localizes in the nucleus; however, the role of N-WASP in the nucleus is unclear. Here, we show that localization of N-WASP is controlled through phosphorylation by Src family kinases in which phosphorylated N-WASP is exported from the nucleus in a nuclear export signal (NES) and leptomycin B-dependent manner. N-WASP had nuclear localization signal (NLS) at its basic region and NES close to the phosphorylation site by Src family kinases, indicating that phosphorylation controls the accessibility to the NES through conformational changes. Increased levels of unphosphorylated N-WASP in the nucleus suppressed expression of HSP90 and transcription from a heat shock element (HSE). N-WASP bound heat shock transcription factor (HSTF) and enhanced the HSTF association with HSE. In addition, nuclear N-WASP was present in the protein complex that associates with HSE, suggesting that N-WASP participates in suppression of HSP90 transcription. Increased levels of unphosphorylated N-WASP also decreased the activities of Src family kinases in cells but not in experiments in vitro with pure N-WASP and Fyn. Because HSP90 is essential for the activities of Src family kinases, these results suggest that localization of N-WASP modulates Src kinase activity by regulating HSP90 expression.

Active Transport, Cell Nucleus↗
PubMed2004

Cellular localization of activated N-WASP using a conformation-sensitive antibody.

The main regulators of Arp2/3 activity appear to be N-WASP and the other members of the Scar/WAVE family of proteins. We show here that after EGF stimulation, N-WASP is recruited to the nucleation zone of the dynamic leading edge compartment of carcinoma cells, with maximal recruitment of N-WASP within 1 min after EGF stimulation. The timing of N-WASP recruitment mirrors the timing of barbed-end formation at the leading edge. To determine the cellular activation of N-WASP after EGF stimulation, we made a conformation-sensitive antibody (CSA) against the CRIB domain of N-WASP that is predicted to recognize N-WASP in its open, active conformation, but not in its closed, inactive conformation. The ability of CSA to detect only active N-WASP was demonstrated by in vitro experiments using immunoprecipitation of active N-WASP from EGF-stimulated cells and Cdc42 activation of N-WASP activity. In cell staining experiments, N-WASP is maximally accessible to CSA 40 sec after EGF stimulation and this activated N-WASP is in the nucleation zone. These results indicate that active N-WASP is present at the leading edge of lamellipods, an unexpected finding given its reported involvement in filopod formation. This work establishes the feasibility of using antibodies directed against specific conformations or epitopes with changing accessibilities as a window on the status and localization of activity.

Actin Cytoskeleton↗
PubMed2006

WASP suppresses the growth defect of Saccharomyces cerevisiae las17Delta strain in the presence of WIP.

Wiskott-Aldrich syndrome is caused by alterations in the Wiskott-Aldrich syndrome protein (WASP) and several of these mutations affect WASP's interaction with WIP (WASP-interacting protein), suggesting that loss of interaction between WASP and WIP is causal to the disease. Las17p is the yeast homologue of WASP and las17Delta strain is unable to grow at 37 degrees C. We show that Human WASP suppresses the growth defect of Saccharomyces cerevisiae las17Delta strain, only in the presence of WIP. WIP mediates cortical localisation of WASP as well as stabilise WASP in yeast cells. Mutations which affected WASP-WIP interaction abolished WASP's ability to suppress the growth defect of las17Delta strain. We have demonstrated that WASP-WIP is an active complex and WASP's ability to suppress the growth defect of las17Delta strain is dependent on the presence of a functional Arp2/3 activating domain of WASP and also the Verprolin domain (V) of WIP.

Amino Acid Motifs↗
PubMed2001

Different WASP family proteins stimulate different Arp2/3 complex-dependent actin-nucleating activities.

BACKGROUND: Assembly and organization of actin filaments are required for many cellular processes, including locomotion and division. In many cases, actin assembly is initiated when proteins of the WASP/Scar family respond to signals from Rho family G proteins and stimulate the actin-nucleating activity of the Arp2/3 complex. Two questions of fundamental importance raised in the study of actin dynamics concern the molecular mechanism of Arp2/3-dependent actin nucleation and how different signaling pathways that activate the same Arp2/3 complex produce actin networks with different three-dimensional architectures? RESULTS: We directly compared the activity of the Arp2/3 complex in the presence of saturating concentrations of the minimal Arp2/3-activating domains of WASP, N-WASP, and Scar1 and found that each induces unique kinetics of actin assembly. In cell extracts, N-WASP induces rapid actin polymerization, while Scar1 fails to induce detectable polymerization. Using purified proteins, Scar1 induces the slowest rate of nucleation. WASP activity is 16-fold higher, and N-WASP activity is 70-fold higher. The data for all activators fit a mathematical model in which one activated Arp2/3 complex, one actin monomer, and an actin filament combine into a preactivation complex which then undergoes a first-order activation step to become a nucleus. The differences between Scar and N-WASP activity are explained by differences in the rate constants for the activation step. Changing the number of actin binding sites on a WASP family protein, either by removing a WH2 domain from N-WASP or by adding WH2 domains to Scar1, has no significant effect on nucleation activity. The addition of a three amino acid insertion found in the C-terminal acidic domains of WASP and N-WASP, however, increases the activity of Scar1 by more than 20-fold. Using chemical crosslinking assays, we determined that both N-WASP and Scar1 induce a conformational change in the Arp2/3 complex but crosslink with different efficiencies to the small molecular weight subunits p18 and p14. CONCLUSION: The WA domains of N-WASP, WASP, and Scar1 bind actin and Arp2/3 with nearly identical affinities but stimulate rates of actin nucleation that vary by almost 100-fold. The differences in nucleation rate are caused by differences in the number of acidic amino acids at the C terminus, so each protein is tuned to produce a different rate of actin filament formation. Arp2/3, therefore, is not regulated by a simple on-off switch. Precise tuning of the filament formation rate may help determine the architecture of actin networks produced by different nucleation-promoting factors.

Actin-Related Protein 2↗
PubMed2004

Erk/Src phosphorylation of cortactin acts as a switch on-switch off mechanism that controls its ability to activate N-WASP.

The Arp2/3 complex can be independently activated to initiate actin polymerization by the VCA domain of WASP family members and by the acidic N-terminal and F-actin-binding repeat region of cortactin, which possesses a C-terminal SH3 domain. Cortactin is a target for phosphorylation by Src tyrosine kinases and by serine/threonine kinases that include Erk. Here we demonstrate that cortactin binds N-WASP and WASP via its SH3 domain, induces in vitro N-WASP-mediated actin polymerization, and colocalizes with N-WASP and WASP at sites of active actin polymerization. Erk phosphorylation and a mimicking S405,418D double mutation enhanced cortactin binding and activation of N-WASP. In contrast, Src phosphorylation inhibited the ability of cortactin previously phosphorylated by Erk, and that of S405,418D double mutant cortactin, to bind and activate N-WASP. Furthermore, Y-->D mutation of three tyrosine residues targeted by Src (Y421, Y466, and Y482) inhibited the ability of S405,418D cortactin to activate N-WASP. We propose that Erk phosphorylation liberates the SH3 domain of cortactin from intramolecular interactions with proline-rich regions, causing it to synergize with WASP and N-WASP in activating the Arp2/3 complex, and that Src phosphorylation terminates cortactin activation of N-WASP and WASP.

Actin-Related Protein 2↗
PubMed1999

WASP levels in platelets and lymphocytes of wiskott-aldrich syndrome patients correlate with cell dysfunction.

Wiskott-Aldrich syndrome, an inherited blood cell disorder due to mutations of the X-chromosome gene WASP (Wiskott-Aldrich syndrome protein), was characterized originally by thrombocytopenia, immunodeficiency, and eczema. Whereas platelet dysfunction is severe and consistent, immune defects are clinically variable, ranging from negligible to life threatening. To understand this heterogeneity, we quantified WASP in PBMC and platelets, and also in neutrophils, of patients with diverse mutations. A surprisingly complex pattern of WASP expression found for lymphoid cells formed the basis for dividing the patient mutations into four groups. Group A have low WASP levels in PBMC and higher levels in EBV cell lines, as well as near normal WASP RNA levels (7 patients, most with mild disease), suggesting that group A WASP molecules are hypersusceptible to proteolysis. Group B have low WASP levels in PBMC and EBV cells and similar low RNA levels (2 patients, moderate disease). Group C have discordant expression: WASP-positive peripheral T cells and WASP-negative peripheral B cells and EBV cell lines (9 patients, variable disease severity). Noteworthy among group C kindred are several instances of B cell lymphomas. In group D, PBMC and EBV cell lines are WASP negative (7 patients, severe disease). In contrast to the complex lymphoid cell expression patterns, all patient platelets examined were WASP negative (18 diverse patients). WASP absence in platelets provides an apparent molecular explanation for the universally severe platelet dysfunction in this disease, and the cumulative lymphoid cell findings suggest that WASP levels play a substantial role in determining immune outcome.

Blood Platelets↗