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PubMed1986

Male-killing bacteria in a parasitic wasp.

A rod-shaped bacterium has been isolated that kills male eggs of the wasp Nasonia vitripennis, a pupal parasite of flies. Only some wasps of this species express this son-killer trait, and these wasps have bacterial infections in various organs. The bacterium was isolated from son-killer wasp tissue and from the hemolymph of fly pupae parasitized by wasps expressing the son-killer trait. Bacteria are apparently transferred to parasitized fly pupae during wasp oviposition, and developing wasp offspring are subsequently infected perorally. Sex-ratio distortion by microorganisms is found in a variety of plants and animals. The infectious peroral transmission of this trait variety of plants and animals. The infectious peroral transmission of this trait is in contrast to the typical pattern of cytoplasmic inheritance of sex-ratio distortion in these other systems.

Animals↗
PubMed2002

Cuticular hydrocarbons of the ectoparasitic wasp Cephalonomia hyalinipennis (Hymenoptera: Bethylidae) and its alternative host, the stored product pest Caulophilus oryzae (Coleoptera: Curculionidae).

Cuticular hydrocarbons of an ectoparasitic wasp attacking two beetle hosts have been identified and examined for the influence of age, gender, mating status, and host on hydrocarbon composition. The 37 wasp hydrocarbons identified consisted of a series of n-alkanes (C16 to C33), 3-, 5-, 9-, 10-, 11-, and 12-methyl alkanes and a series of Z-7 and Z-9 monoenes (C23:1 to C27:1). One C25:2 diene was found. No effects of hydrocarbon composition as a function of age, gender, or mating status were found for the wasps. Wasps reared on Hypothenemus hampei, however, had 12/37 significant abundance differences to those reared on Caulophilus oryzae, although all but one of these differences were for components in less than 2% relative abundance. The C25:2 diene from wasps reared on H. hampei was present in about 10% whereas from wasps reared on C. oryzae it was present in about 2%. The hydrocarbons of one host for this wasp, the coffee berry borer (Coleoptera: Scolytidae), have been previously reported [Howard and Infante, Ann. Entomol. Soc. Am. 89:700-709 (1996)]. The hydrocarbons of the alternative host, C. oryzae (Coleoptera: Curculionidae) consists of n-alkanes (C17 to C31), 3-, 4-, 5-, 7-, 9-, 11-, 12-, 13-, 14-, and 15-methyl alkanes, and a series of dimethyl alkanes of the series 3, 17-; 5, 11-; 5, 17-; 7, 11-; 7, 13-; 13, 17-; and 15, 19-. No unsaturated hydrocarbons were found. No significant differences in hydrocarbon composition were found between male and female C. oryzae. Hydrocarbon patterns of four species of Cephalonomia are compared and shown to be species-specific. The data are discussed in terms of ecological and physiological parameters.

Animals↗
PubMed2001

Requirement of the basic region of N-WASP/WAVE2 for actin-based motility.

WASP family proteins activate nucleation by the Arp2/3 complex, inducing rapid actin polymerization in vitro. Although the C-terminal portion of WASP family proteins (VCA) activates nucleation by the Arp2/3 complex in pure systems, we find that this fragment lacks activity in cell extracts. Thus, polystyrene beads coated with VCA did not move in brain cytosol, while beads coated with N-WASP or WAVE2 did move. The basic clusters between the WH1 domain and the CRIB domain of N-WASP were critical for movement since beads coated with N-WASP or WAVE2 constructs missing the basic clusters (Delta basic) also did not move. Furthermore, VCA and N-WASP/WAVE2 Delta basic constructs were much less able than wild-type N-WASP and WAVE2 to induce actin polymerization in cytosol. All of the proteins, with or without the basic domain, were potent activators of nucleation by purified Arp2/3 complex.

Actins↗
PubMed2006

WIP regulates the stability and localization of WASP to podosomes in migrating dendritic cells.

The Wiskott-Aldrich Syndrome protein (WASP) is an adaptor protein that is essential for podosome formation in hematopoietic cells. Given that 80% of identified Wiskott-Aldrich Syndrome patients result from mutations in the binding site for WASP-interacting-protein (WIP), we examined the possible role of WIP in the regulation of podosome architecture and cell motility in dendritic cells (DCs). Our results show that WIP is essential both for the formation of actin cores containing WASP and cortactin and for the organization of integrin and integrin-associated proteins in circular arrays, specific characteristics of podosome structure. We also found that WIP is essential for the maintenance of the high turnover of adhesions and polarity in DCs. WIP exerts these functions by regulating calpain-mediated cleavage of WASP and by facilitating the localization of WASP to sites of actin polymerization at podosomes. Taken together, our results indicate that WIP is critical for the regulation of both the stability and localization of WASP in migrating DCs and suggest that WASP and WIP operate as a functional unit to control DC motility in response to changes in the extracellular environment.

Actins↗
PubMed2006

Retroviral WASP gene transfer into human hematopoietic stem cells reconstitutes the actin cytoskeleton in myeloid progeny cells differentiated in vitro.

OBJECTIVE: Wiskott-Aldrich syndrome (WAS) is a primary immunodeficiency disorder characterized by recurrent infections, autoimmunity, microthrombocytopenia, and susceptibility to malignant tumors. Compared with the conventional treatment using allogeneic bone marrow transplantation, hematopoietic stem cell gene therapy might offer more specific and less toxic therapeutic options. METHODS: We investigated retroviral WAS protein (WASP) gene transfer to assess functional correction and potential toxicities in human CD34(+) cells from WAS patients and healthy individuals, respectively. RESULTS: WASP mRNA and protein levels were restored in CD14(+) cells derived from WASP-transduced hematopoietic stem cells. Functional reconstitution in WASP-transduced myeloid cells was documented by podosome formation and Fc gamma R-mediated phagocytosis. Importantly, overexpression of WASP in CD34(+) cells from healthy donors did not cause any discernible toxic effects. CONCLUSIONS: Our studies document the feasibility of WASP gene transfer into human CD34(+) cells and suggest that the phenotype of WASP-deficient myeloid cells can be restored upon retroviral gene transfer.

Actin Cytoskeleton↗
PubMed2003

X-linked thrombocytopenia caused by a mutation in the Wiskott-Aldrich syndrome (WAS) gene that disrupts interaction with the WAS protein (WASP)-interacting protein (WIP).

OBJECTIVE: We studied two adult brothers with severe congenital thrombocytopenia in order to determine the genetic etiology of their inherited disorder. Despite the absence of eczema or immunodeficiency, a mutation of the Wiskott-Aldrich syndrome (WAS) gene was suspected because of the presence of microthrombocytes. MATERIALS AND METHODS: Peripheral blood was obtained for characterization of hematopoietic cells and megakaryocyte progenitors. The coding region of the WAS gene was fully sequenced, and expression of the Wiskott-Aldrich syndrome protein, WASP, was evaluated by immunoblotting. The ability of WASP to physically associate with the WASP-interacting protein, WIP, was tested by yeast and mammalian two-hybrid techniques. RESULTS: In addition to thrombocytopenia, our investigation revealed an increased frequency of peripheral megakaryocyte progenitors (CFU-Mk) and incomplete cytoplasmic maturation by electron microscopy. Sequencing the WAS gene revealed a single base mutation, resulting in substitution of proline for arginine 138 (i.e., Arg138Pro). Immunoblotting demonstrated reduced expression of the mutant WAS protein, and we showed that the Arg138Pro mutation significantly, but incompletely, disrupts WASP-WIP interaction. CONCLUSIONS: In this pedigree, X-linked thrombocytopenia is caused by a rare mutation in the fourth exon of the WAS gene. WASP levels are reduced in lymphocyte cell lines derived from the affected individuals. Furthermore, the mutation significantly but incompletely disrupts WASP-WIP interaction, whereas substitution of alanine or glutamic acid residues at the same position does not. This raises the possibility that protein-protein interaction and WASP stability are related properties.

Adaptor Proteins, Signal Transducing↗
PubMed2003

A WASp homolog powers actin polymerization-dependent motility of endosomes in vivo.

BACKGROUND: WASp/SCAR proteins activate the Arp2/3 complex to nucleate actin filament assembly and are thought to have important roles in endocytosis. WASp is required for efficient endocytosis of antigen receptors, N-WASp promotes actin polymerization-dependent movement of endomembrane vesicles, and Las17 (a yeast WASp homolog) is required for endocytic internalization. However, it is unknown whether movement of endosomes or other organelles requires activation of the Arp2/3 complex by members of the WASp/SCAR family. RESULTS: Fluorescence video microscopy of yeast cells expressing a GFP-tagged G protein-coupled receptor (Ste2-GFP) as an endocytic marker revealed that endosomes and the lysosome-like vacuole are highly motile. Endosome/vacuole motility required actin polymerization, as indicated by sensitivity to latrunculin A, whereas microtubules were uninvolved. Endosome/vacuole motility did not require actin cables or myosin V (a MYO2 gene product), which moves secretory vesicles and the Golgi apparatus and mediates vacuole segregation. However, endosome motility required Las17, a WASp homolog. In contrast to other processes involving Las17, endosome/vacuole motility required the WCA domain of Las17, which is necessary and sufficient to activate the Arp2/3 complex. CONCLUSIONS: Endosome/vacuole motility in vivo requires actin polymerization stimulated by the WASp homolog Las17. WASp/SCAR family members in mammalian cells may have similar functions. Defects in endosome/lysosome motility may contribute to deficits in lymphocyte or macrophage function observed in human patients lacking WASp or developmental defects in N-WASp-deficient mice.

Actins↗
PubMed2002

Mechanism of recruitment of WASP to the immunological synapse and of its activation following TCR ligation.

F-actin polymerization following engagement of the T cell receptor (TCR) is dependent on WASP and is critical for T cell activation. The link between TCR and WASP is not fully understood. In resting cells, WASP exists in a complex with WIP, which inhibits its activation by Cdc42. We show that the adaptor protein CrkL binds directly to WIP. Further, TCR ligation results in the formation of a ZAP-70-CrkL-WIP-WASP complex, which is recruited to lipid rafts and the immunological synapse. TCR engagement also causes PKCtheta-dependent phosphorylation of WIP, causing the disengagement of WASP from the WIP-WASP complex, thereby releasing it from WIP inhibition. These results suggest that the ZAP-70-CrkL-WIP pathway and PKCtheta link TCR to WASP activation.

Actins↗
PubMed2002

Sustained activation of N-WASP through phosphorylation is essential for neurite extension.

Neurite extension is a key process for constructing neuronal circuits during development and remodeling of the nervous system. Here we show that Src family tyrosine kinases and proteasome degradation signals synergistically regulate N-WASP in neurite extension. Src family kinases activate N-WASP through tyrosine phosphorylation, which induces Arp2/3 complex-mediated actin polymerization. Tyrosine phosphorylation of N-WASP also initiates its degradation through ubiquitination. When neurite growth is stimulated in culture, degradation of N-WASP is markedly inhibited, leading to accumulation of the phosphorylated N-WASP. On the other hand, under culture conditions that inhibit neurite extension, but favor proliferation, the phosphorylated N-WASP is degraded rapidly. Collectively, neurite extension is regulated by the balance of N-WASP phosphorylation (activation) and degradation (inactivation), which are induced by tyrosine phosphorylation.

Acetylcysteine↗
PubMed2001

WIP regulates N-WASP-mediated actin polymerization and filopodium formation.

Induction of filopodia is dependent on activation of the small GTPase Cdc42 and on neural Wiskott-Aldrich-syndrome protein (N-WASP). Here we show that WASP-interacting protein (WIP) interacts directly with N-WASP and actin. WIP retards N-WASP/Cdc42-activated actin polymerization mediated by the Arp2/3 complex, and stabilizes actin filaments. Microinjection of WIP into NIH 3T3 fibroblasts induces filopodia; this is inhibited by microinjection of anti-N-WASP antibody. Microinjection of anti-WIP antibody inhibits induction of filopodia by bradykinin, by an active Cdc42 mutant (Cdc42(V12)) and by N-WASP. Our results indicate that WIP and N-WASP may act as a functional unit in filopodium formation, which is consistent with their role in actin-tail formation in cells infected with vaccinia virus or Shigella.

3T3 Cells↗
PubMed2001

A phosphatidylinositol 3-kinase-independent insulin signaling pathway to N-WASP/Arp2/3/F-actin required for GLUT4 glucose transporter recycling.

Recruitment of intracellular glucose transporter 4 (GLUT4) to the plasma membrane of fat and muscle cells in response to insulin requires phosphatidylinositol (PI) 3-kinase as well as a proposed PI 3-kinase-independent pathway leading to activation of the small GTPase TC10. Here we show that in cultured adipocytes insulin causes acute cortical localization of the actin-regulatory neural Wiskott-Aldrich syndrome protein (N-WASP) and actin-related protein-3 (Arp3) as well as cortical F-actin polymerization by a mechanism that is insensitive to the PI 3-kinase inhibitor wortmannin. Expression of the dominant inhibitory N-WASP-DeltaWA protein lacking the Arp and actin binding regions attenuates the cortical F-actin rearrangements by insulin in these cells. Remarkably, the N-WASP-DeltaWA protein also inhibits insulin action on GLUT4 translocation, indicating dependence of GLUT4 recycling on N-WASP-directed cortical F-actin assembly. TC10 exhibits sequence similarity to Cdc42 and has been reported to bind N-WASP. We show the inhibitory TC10 (T31N) mutant, which abrogates insulin-stimulated GLUT4 translocation and glucose transport, also inhibits both cortical localization of N-WASP and F-actin formation in response to insulin. These findings reveal that N-WASP likely functions downstream of TC10 in a PI 3-kinase-independent insulin signaling pathway to mobilize cortical F-actin, which in turn promotes GLUT4 responsiveness to insulin.

Actin-Related Protein 2↗
PubMed2001

A novel neural Wiskott-Aldrich syndrome protein (N-WASP) binding protein, WISH, induces Arp2/3 complex activation independent of Cdc42.

We identified a novel adaptor protein that contains a Src homology (SH)3 domain, SH3 binding proline-rich sequences, and a leucine zipper-like motif and termed this protein WASP interacting SH3 protein (WISH). WISH is expressed predominantly in neural tissues and testis. It bound Ash/Grb2 through its proline-rich regions and neural Wiskott-Aldrich syndrome protein (N-WASP) through its SH3 domain. WISH strongly enhanced N-WASP-induced Arp2/3 complex activation independent of Cdc42 in vitro, resulting in rapid actin polymerization. Furthermore, coexpression of WISH and N-WASP induced marked formation of microspikes in Cos7 cells, even in the absence of stimuli. An N-WASP mutant (H208D) that cannot bind Cdc42 still induced microspike formation when coexpressed with WISH. We also examined the contribution of WISH to a rapid actin polymerization induced by brain extract in vitro. Arp2/3 complex was essential for brain extract-induced rapid actin polymerization. Addition of WISH to extracts increased actin polymerization as Cdc42 did. However, WISH unexpectedly could activate actin polymerization even in N-WASP-depleted extracts. These findings suggest that WISH activates Arp2/3 complex through N-WASP-dependent and -independent pathways without Cdc42, resulting in the rapid actin polymerization required for microspike formation.

Actin-Related Protein 2↗
PubMed2001

The intersectin 2 adaptor links Wiskott Aldrich Syndrome protein (WASp)-mediated actin polymerization to T cell antigen receptor endocytosis.

Induction of T cell antigen receptor (TCR) endocytosis has a significant impact on TCR signaling and T cell behavior, but the molecular interactions coordinating internalization of the activated TCR are poorly understood. Previously we have shown that TCR endocytosis is regulated by the Wiskott Aldrich Syndrome protein (WASp), a cytosolic effector which, upon interaction with the cdc42 Rho GTPase, couples TCR engagement to Arp 2/3 complex-mediated actin polymerization. Here we report that WASp associates in T cells with intersectin 2, an endocytic adaptor containing multiple domains including a Dbl homology (DH) domain with the potential to activate Rho GTPases. Intersectin 2 association with WASp increases after TCR engagement, and its overexpression in Cos-7 cells induces WASp translocation to endocytic vesicles within which intersectin 2 colocalizes with both WASp and cdc42. Intersectin 2, but not a DH domain-deleted (DeltaDH) form of intersectin 2, and stimulation via the TCR also trigger the activation of cdc42. Induction of TCR internalization is also augmented by intersectin 2 and severely impaired by latrunculin B treatment. Thus, intersection 2 appears to function cooperatively with WASp and cdc42 to link the clathrin endocytic machinery to WASp-mediated actin polymerization and ultimately to occupancy-induced TCR endocytosis.

Actins↗
PubMed2006

N-WASP involvement in dorsal ruffle formation in mouse embryonic fibroblasts.

The Wiskott-Aldrich syndrome protein (WASP) family activates the Arp2/3 complex leading to the formation of new actin filaments. Here, we study the involvement of Scar1, Scar2, N-WASP, and Arp2/3 complex in dorsal ruffle formation in mouse embryonic fibroblasts (MEFs). Using platelet-derived growth factor to stimulate circular dorsal ruffle assembly in primary E13 and immortalized E9 Scar1(+/+) and Scar1 null MEFs, we establish that Scar1 loss does not impair the formation of dorsal ruffles. Reduction of Scar2 protein levels via small interfering RNA (siRNA) also did not affect dorsal ruffle production. In contrast, wiskostatin, a chemical inhibitor of N-WASP, potently suppressed dorsal ruffle formation in a dose-dependent manner. Furthermore, N-WASP and Arp2 siRNA treatment significantly decreased the formation of dorsal ruffles in MEFs. In addition, the expression of an N-WASP truncation mutant that cannot bind Arp2/3 complex blocked the formation of these structures. Finally, N-WASP(-/-) fibroblast-like cells generated aberrant dorsal ruffles. These ruffles were highly unstable, severely depleted of Arp2/3 complex, and diminished in size. We hypothesize that N-WASP and Arp2/3 complex are part of a multiprotein assembly important for the generation of dorsal ruffles and that Scar1 and Scar2 are dispensable for this process.

Actin Cytoskeleton↗
PubMed2003

Direct injection of venom by a predatory wasp into cockroach brain.

In this article, we provide direct evidence for injection of venom by a wasp into the central nervous system of its cockroach prey. Venomous predators use neurotoxins that generally act at the neuromuscular junction, resulting in different types of prey paralysis. The sting of the parasitoid wasp Ampulex compressa is unusual, as it induces grooming behavior, followed by a long-term lethargic state of its insect prey, thus ultimately providing a living meal for the newborn wasp larvae. These behavioral modifications are induced only when a sting is inflicted into the head. These unique effects of the wasp venom on prey behavior suggest that the venom targets the insect's central nervous system. The mechanism by which behavior modifying compounds in the venom transverse the blood-brain barrier to induce these central and long-lasting effects has been the subject of debate. In this article, we demonstrate that the wasp stings directly into the target ganglia in the head of its prey. To prove this assertion, we produced "hot" wasps by injecting them with (14)C radiolabeled amino acids and used a combination of liquid scintillation and light microscopy autoradiography to trace radiolabeled venom in the prey. To our knowledge, this is the first direct evidence documenting targeted delivery of venom by a predator into the brain of its prey.

Animals↗
PubMed1999

Evaluation of the risk of anaphylactic reactions by wasp venom-extract challenges in children.

Diagnostic sting challenges have been shown to provide information on the risk of further anaphylactic reactions to bee stings. We present a follow-up study in wasp venom-hypersensitive children after diagnostic venom extract challenges to analyze their risk of further anaphylactic reactions. Responses were obtained from 104 patients with wasp venom hypersensitivity out of 115 former patients. Only one of the 104 patients showed more than a severe local reaction to the sting challenge irrespective of the performance of a single or sequential challenge; therefore, only one patient received venom immunotherapy. The performance of a diagnostic sting challenge with wasp venom extract in children had a high negative predictive value of 94.6% for the risk of further systemic reactions. This was shown by analysis of later field stings, since 37 children experienced further field stings and only two of these children(5.4%) developed a mild systemic reaction (urticaria) equal to or less severe than the index sting. The value of the venom extract challenge can be interpreted in two ways: either it is less sensitive than a native sting challenge since the rate of systemic reactions to the challenge was very low, or the prognosis of wasp venom hypersensitivity in children is extremely favorable. Since the latter hypothesis is supported by the low incidence of systemic field sting reactions, we postulate that venom immunotherapy is necessary only in a minority of children with wasp venom hypersensitivity with an index sting reaction of Mueller grade I or II. However, the value of venom extract challenges as a general diagnostic instrument in children with Mueller I and II reactions due to wasp venom hypersensitivity may be questioned. It may have a place as a safe procedure in demonstrating to parents and physicians the often self-limiting natural course in most of these children.

Adolescent↗
PubMed2000

Insect immunity: a genetic factor (hrtp) is essential for antibacterial peptide expression in Drosophila after infection by parasitoid wasps.

We have used a parasitoid wasp Drosophila melanogaster system to investigate the relationship between the humoral and cellular immune responses in insects. Expression of the gene encoding diptericin, an antibacterial peptide in various D. melanogaster strains parasitized by several species of parasitoid wasps, was studied by Northern blot. These strains have the capacity to encapsulate parasitoid eggs. Two strains appeared to produce diptericin mRNA after parasitoid challenge, regardless of their cellular immune reaction to the wasp species. This suggests that a specific genetic factor, or factors, here designated humoral response to parasitoid (hrtp), is present in these two strains of D. melanogaster and is implicated in the expression of the antibacterial gene after parasite infection. This hrtp genetic factor is recessively expressed and located on the second chromosome, suggesting that it is monofactorial. The transgenic strain Dipt.2.2-lacZ:1, in which the transgene is present on the first chromosome, is normally susceptible to the parasitoid wasp. The chromosome bearing the hrtp factor was transferred to this transgenic strain, which then became reactive when triggered by wasp infection. The hrtp factor appears necessary for the activation of diptericin by the parasitoid wasp. No correlation between the cellular immune capacity and the humoral response was observed, suggesting that the two components of insect immunity are regulated independently. Arch.

Animals↗
PubMed2006

Visual adaptations in the night-active wasp Apoica pallens.

The apposition compound eye of the nocturnal polistine wasp Apoica pallens shows, in comparison to the closely related diurnal wasp Polistes occidentalis, specific adaptations to vision at low light intensities. When considering recent work on nocturnal and diurnal bees, general principles for dim-light vision in hymenopterans become evident: The rhabdom diameters in nocturnal bees and wasps are 4 times wider compared to their diurnal relatives, leading to wide receptive fields, which in turn account for a 25-fold higher optical sensitivity. Interestingly, the rhabdom diameters in both nocturnal bees and wasps measure 8 mum, which may represent the maximum width for nocturnal hymenopteran apposition eyes. A ratio of 1.8 times larger eyes is present in the nocturnal bees and wasps, which in A. pallens is achieved by increasing the facet number, instead of enlarging the facets, as in nocturnal bees. Although this initially indicates spatial resolution to be important for the nocturnal wasp, the wide receptive fields of the rhabdoms will reduce its potentially high acuity. As the optical sensitivity alone cannot account for the 8 log units intensity difference between day and night, a possible role of neural summation within the first optic ganglion (lamina) of nocturnal hymenopterans is discussed.

Animals↗