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PubMed2003

A conserved amphipathic helix in WASP/Scar proteins is essential for activation of Arp2/3 complex.

Members of the Wiskott-Aldrich syndrome protein (WASP) family link Rho GTPase signaling pathways to the cytoskeleton through a multiprotein assembly called Arp2/3 complex. The C-terminal VCA regions (verprolin-homology, central hydrophobic, and acidic regions) of WASP and its relatives stimulate Arp2/3 complex to nucleate actin filament branches. Here we show by differential line broadening in NMR spectra that the C (central) and A (acidic) segments of VCA domains from WASP, N-WASP and Scar bind Arp2/3 complex. The C regions of these proteins have a conserved sequence motif consisting of hydrophobic residues and an arginine residue. Point mutations in this conserved sequence motif suggest that it forms an amphipathic helix that is required in biochemical assays for activation of Arp2/3 complex. Key residues in this motif are buried through contacts with the GTPase binding domain in the autoinhibited structure of WASP and N-WASP, indicating that sequestration of these residues is an important aspect of autoinhibition.

Actin-Related Protein 2↗

PubMed2006

Wiskott-Aldrich syndrome protein is involved in alphaIIb beta3-mediated cell adhesion.

The Wiskott-Aldrich syndrome (WAS) is an X-chromosome-linked immunodeficiency disorder. The most common symptom seen in WAS patients is bleeding. One of the main causes of bleeding is defective platelet aggregation. The causative gene of WAS encodes WAS protein (WASP). Here, we show that WASP binds to the calcium- and integrin-binding protein (CIB) in platelets. CIB was originally identified as a protein binding to the alphaIIb cytoplasmic tail of platelet integrin alphaIIb beta3, which has a primary role in platelet aggregation. We also show that the WASP-CIB complex is important in alphaIIb beta3-mediated cell adhesion, and that in patients mutant forms of WASP are expressed at reduced levels or show lower affinities for CIB than wild-type WASP. Our results indicate that impaired complex formation between mutant WASPs and CIB reduces alphaIIb beta3-mediated cell adhesion and causes defective platelet aggregation, resulting in bleeding.

Blood Platelets↗

PubMed2000

Expression of human Wiskott-Aldrich syndrome protein in patients' cells leads to partial correction of a phenotypic abnormality of cell surface glycoproteins.

The Wiskott-Aldrich syndrome (WAS) is an uncommon X-linked recessive disease characterized by thrombocytopenia, eczema and immunodeficiency. The biochemical defect of this disorder primarily affects cells derived from bone marrow. To understand better the molecular mechanisms underlying this disease and to evaluate the possibility of correcting the genetic defects in hematopoietic cells, a Moloney murine leukemia virus (MoMLV)- based retroviral vector carrying a functional Wiskott-Aldrich syndrome protein (WASp) cDNA driven by an SV40 promoter (LNS-WASp) was constructed. A packaging cell line containing this vector produced a stable level of WAS protein and maintained a high titer of viral output. Epstein-Barr virus (EBV)-transformed B lymphoblastoid cell lines (B-LCL) from WAS patients, which lack expression of the WAS protein, were transduced by the LNS-WASp retroviral vector and showed expression of WASp by Western blot. Analysis of the O-glycan pattern on cell surface glycoproteins from WAS patients' B-LCL showed an altered glycosylation pattern, due to increased activity of beta-1, 6-N-acetylglucosaminyltransferase (C2GnT). Transduction by the retroviral vector carrying the functional WASp cDNA partially restored the abnormal glycosylation pattern, and was accompanied by a decreasing C2GnT activity. These findings imply a functional linkage between the WAS protein and the expression of the glycosyltransferase involved in the O-glycosylation, and also suggest a potential gene therapy via transferring a functional WASp cDNA into hematopoietic cells for Wiskott-Aldrich syndrome. Gene Therapy (2000) 7, 314-320.

Cells, Cultured↗

PubMed2001

Protein assays for diagnosis of Wiskott-Aldrich syndrome and X-linked thrombocytopenia.

Mutations in the gene encoding the Wiskott-Aldrich syndrome protein (WASp) give rise to Wiskott-Aldrich syndrome (WAS), a condition that exhibits a wide spectrum of clinical severity. Patients may develop mild thrombocytopenia or suffer from a wide range of associated disorders including eczema, immune dysfunction, autoimmune disease and malignancy. The clinical diagnosis of Wiskott-Aldrich syndrome (WAS) can be difficult and is usually supported by the detection of WASp gene mutations using genetic analysis. Recently, protein-based assays have been used to demonstrate the absence of WASp in patients known to have WASp gene mutations. We have now reversed this approach and report on the use of immunoblot assays to rapidly diagnose WAS in 13 patients. There was a complete absence of WASp in 10 out of 13 patients and an abnormal protein form was detected in the remaining three patients. In all cases, subsequent genetic analysis confirmed the presence of a WASp gene mutation. We believe that protein-based assays should be employed as the first line of investigation in the diagnosis of WAS spectrum disorders.

Aged↗

PubMed2000

Essential role of neural Wiskott-Aldrich syndrome protein in neurite extension in PC12 cells and rat hippocampal primary culture cells.

Neural Wiskott-Aldrich syndrome protein (N-WASP) is an actin-regulating protein that induces filopodium formation downstream of Cdc42. It has been shown that filopodia actively extend from the growth cone, a guidance apparatus located at the tip of neurites, suggesting their role in neurite extension. Here we examined the possible involvement of N-WASP in the neurite extension process. Since verprolin, cofilin homology and acidic region (VCA) of N-WASP is known to be required for the activation of Arp2/3 complex that induces actin polymerization, we prepared a mutant (Deltacof) lacking four amino acid residues in the cofilin homology region. The corresponding residues in WASP had been reported to be mutated in some Wiskott-Aldrich syndrome patients. Expression of Deltacof N-WASP suppressed neurite extension of PC12 cells. In support of this, the VCA region of Deltacof cannot activate Arp2/3 complex enough compared with wild-type VCA. Furthermore, H208D mutant, which has been shown unable to bind to Cdc42, also works as a dominant negative mutant in neurite extension assay. Interestingly, the expression of H208D-Deltacof double mutant has no significant dominant negative effect. Finally, the expression of the Deltacof mutant also severely inhibited the neurite extension of primary neurons from rat hippocampus. Thus, N-WASP is thought to be a general regulator of the actin cytoskeleton indispensable for neurite extension, which is probably caused through Cdc42 signaling and Arp2/3 complex-induced actin polymerization.

Actin Depolymerizing Factors↗

PubMed2000

Profilin is required for sustaining efficient intra- and intercellular spreading of Shigella flexneri.

The ability of Shigella to mediate actin-based motility within the host cell is a prominent pathogenic feature of bacillary dysentery. The ability is dependent on the interaction of VirG with neural Wiskott-Aldrich syndrome protein (N-WASP), which in turn mediates recruitment of Arp2/3 complex and several actin-related proteins. In the present study, we show that profilin I is essential to the rapid movement of Shigella in epithelial cells, for which the capacity of profilin to interact with G-actin and N-WASP is critical. In COS-7 cells overexpressing either mutated profilin H119E, which failed to bind G-actin, or H133S, which is unable to interact with poly-l-proline, Shigella motility was significantly inhibited. Similarly, depletion of profilin from Xenopus egg extracts resulted in a decrease in bacterial motility that was completely rescued by adding back profilin I but not H119E or H133S. In COS-7 cells overexpressing a N-WASP mutant lacking the proline-rich domain (Deltap) unable to interact with profilin, the actin tail formation of intracellular Shigella was inhibited. In N-WASP-depleted extracts, addition of Deltap but not full-length N-WASP was unable to restore the bacterial motility. Furthermore, in a plaque formation assay with Madin-Darby canine kidney cell monolayers infected by Shigella, Madin-Darby canine kidney cells stably expressing H119E, H133S, or Deltap reduced the bacterial cell-to-cell spreading. These results indicate that profilin I associated with N-WASP is an essential host factor for sustaining efficient intra- and intercellular spreading of Shigella.

Actins↗

PubMed2001

The verprolin-like central (vc) region of Wiskott-Aldrich syndrome protein induces Arp2/3 complex-dependent actin nucleation.

Wiskott-Aldrich Syndrome protein (WASp) and related proteins stimulate actin filament nucleation by Arp2/3 complex. The isolated C-terminal VCA domain of WASp (containing Verprolin-like, Central and Acidic regions) is constitutively active but autoinhibited in the full-length protein. This study compared the ability of parts of VCA fused to the C terminus of glutathione S-transferase (GST) to bind actin and Arp2/3 complex in vitro and to activate actin polymerization in vitro and in cells. Fluorescence anisotropy measurements showed that GST-CA and GST-A bound Arp2/3 complex with K(d) values of 0.11 microm and 1.0 microm, respectively, whereas GST-VC displayed almost undetectable binding (K(d) > 1 mm). However, GST-VC activated actin nucleation through Arp2/3 complex in vitro, though requiring 70-fold higher concentration than GST-VCA while neither GST-CA nor GST-A activated Arp2/3 complex in vitro, though both GST-CA and GST-A inhibited Arp2/3 complex activation by WASp VCA. None of these constructs bound WASp from macrophage lysates. Both GST-VC and GST-CA induced actin accumulations when microinjected into primary human macrophages or human endothelial vein cells. However, only microinjection of GST-VC led to a significant increase of cellular polymerized actin. Additionally, endogenous Arp2/3 complex, but not WASp, colocalized with these GST-VC-induced actin accumulations. These data suggest that WASp constructs lacking the A region, previously thought to be indispensable for actin nucleation, are able to bind and activate Arp2/3 complex in vitro and in vivo.

Actin-Related Protein 2↗

PubMed2002

A phylogenetic study of pollinator conservatism among sexually deceptive orchids.

Orchids of the genus Chiloglottis are pollinated through the sexual deception of male wasps mainly from the genus Neozeleboria (Tiphiidae: Thynninae). The orchids mimic both the appearance and sex pheromones of wingless female thynnines but provide no reward to the deceived males. Despite the asymmetry of this interaction, strong pollinator specificity is typical. Such plant-pollinator interactions would seem to be relatively flexible in the plant's adaptive response to variation in the local pollinator resource. However, we present DNA sequence data on both orchids and wasps that demonstrate a pattern of pollinator conservatism operating at a range of taxonomic levels. Sequence data from the wasps indicate 15 of 16 Chiloglottis pollinators are closely related members of one clade of Thynninae. A pattern of congruence between orchid and wasp phylogenies is also demonstrated below the generic level, such that related orchids tend to use related thynnine wasps as specific pollinators. Comparative physiological data on the wasp responses to the floral scents of two Chiloglottis species and one outgroup, Arthrochilus, indicate similar attractive volatile chemicals are used by related orchid taxa. By extension, we infer a similarity of sex pheromone signals among related thynnines. Thus, the conservative pattern of pollinator change in sexually deceptive orchids may reflect phylogenetic patterns in the sex pheromones of their pollinators.

Base Sequence↗

PubMed2004

Bracoviruses contain a large multigene family coding for protein tyrosine phosphatases.

The relationship between parasitic wasps and bracoviruses constitutes one of the few known mutualisms between viruses and eukaryotes. The virions produced in the wasp ovaries are injected into host lepidopteran larvae, where virus genes are expressed, allowing successful development of the parasite by inducing host immune suppression and developmental arrest. Bracovirus-bearing wasps have a common phylogenetic origin, and contemporary bracoviruses are hypothesized to have been inherited by chromosomal transmission from a virus that originally integrated into the genome of the common ancestor wasp living 73.7 +/- 10 million years ago. However, so far no conserved genes have been described among different braconid wasp subfamilies. Here we show that a gene family is present in bracoviruses of different braconid wasp subfamilies (Cotesia congregata, Microgastrinae, and Toxoneuron nigriceps, Cardiochilinae) which likely corresponds to an ancient component of the bracovirus genome that might have been present in the ancestral virus. The genes encode proteins belonging to the protein tyrosine phosphatase family, known to play a key role in the control of signal transduction pathways. Bracovirus protein tyrosine phosphatase genes were shown to be expressed in different tissues of parasitized hosts, and two protein tyrosine phosphatases were produced with recombinant baculoviruses and tested for their biochemical activity. One protein tyrosine phosphatase is a functional phosphatase. These results strengthen the hypothesis that protein tyrosine phosphatases are involved in virally induced alterations of host physiology during parasitism.

Amino Acid Sequence↗

PubMed2005

Mosaicism of NK cells in a patient with Wiskott-Aldrich syndrome.

Rare cases of somatic mosaicism resulting from reversion of inherited mutations can lead to the attenuation of blood-cell disorders, including Wiskott-Aldrich syndrome (WAS). The impact of the revertant hematopoietic stem or progenitor cells, particularly their representation in blood-cell populations, is of interest because it predicts the outcome of gene therapy. Here we report an 8-year-old patient with WAS caused by a single nucleotide insertion in the WASP gene that abrogates protein expression. The patient nonetheless had mild disease. We found reversion of the mutation in a fraction of patient lymphocytes. Forty percent of natural killer (NK) cells expressed Wiskott-Aldrich syndrome protein (WASP), and NK cells contained both mutated and revertant (normal) sequences. WASP was not expressed in patient T or B cells; T cells contained only the mutated sequence. The selective advantage of WASP+ NK cells was also demonstrated for carrier females. The enrichment of WASP+-revertant NK cells indicates that WASP provides a selective advantage in this lineage and predicts the success of gene therapy for reconstituting the NK-cell compartment. The importance of reconstituting the NK-cell lineage is discussed.

Base Sequence↗

PubMed2006

Deficiency in the Wiskott-Aldrich protein induces premature proplatelet formation and platelet production in the bone marrow compartment.

The pathophysiology of microthrombocytopenia in the Wiskott-Aldrich syndrome (WAS) and its milder form, X-linked thrombocytopenia (XLT), is unclear. Although quantitative defects are correctable by splenectomy, residual platelet abnormalities are suggestive of intrinsic disturbances of production. In contrast to human patients, murine models of WASp deficiency exhibit only mild thrombocytopenia, and platelets are of normal size. Here, we have identified a critical role for WASp during murine platelet biogenesis. By electron microscopy, WASp-deficient MKs appeared to have shed platelets ectopically within the bone marrow space. WASp-deficient megakaryocytes (MKs) also displayed defects in response to fibrillar collagen I (CI) in vitro, the major matrix component of bone. These included a loss of normal CI receptor (alpha2beta1 integrin)-mediated inhibition of proplatelet formation, a marked abrogation of SDF-1-induced chemotactic migration of CD41+ MKs adherent to CI, and an almost complete lack of actin-rich podosomes, normally induced by interaction between CI and its receptors GPVI or alpha2beta1 integrin. These findings highlight the central and highly specialized role of WASp in MKs during platelet biogenesis, and may provide a mechanism for the mild thrombocytopenia observed in WASp-deficient mice. In addition, they suggest a novel explanation for some of the platelet abnormalities characteristic of patients with WAS.

Animals↗

PubMed2001

Cdc42, Rac1, and the Wiskott-Aldrich syndrome protein are involved in the cytoskeletal regulation of B lymphocytes.

Patients with the immunodeficiency disorder Wiskott-Aldrich syndrome (WAS) have lymphocytes with aberrant microvilli, and their T cells, macrophages, and dendritic cells are impaired in cytoskeletal-dependent processes. WAS is caused by a defective or a missing WAS protein (WASP). Signal mediators interleukin-4 (IL-4) and CD40 are important for actin-dependent morphology changes in B cells. A possible function of WASP and its interacting partners, Cdc42 and Rac1, was investigated for these changes. It was found that active Cdc42 and Rac1 induced filopodia and lamellipodia, respectively, in activated B cells. Evidence is given that IL-4 has a specific role in the regulated cycling of Cdc42 because IL-4 partially and transiently depleted active Cdc42 from detergent extract of activated B cells. WASP-deficient B lymphocytes were impaired in IL-4-- and CD40-dependent induction of polarized and spread cells. Microvilli were expressed on WASP-deficient B cells, but they appeared shorter and less dense in cell contacts than in wild-type cells. In conclusion, evidence is provided for the involvement of Cdc42, Rac1, and WASP in the cytoskeletal regulation of B lymphocytes. Aberrations in WASP-deficient B lymphocytes, described here, provide further evidence that WAS is a cytoskeletal disease of hematopoietic cells. (Blood. 2001;98:1086-1094)

Animals↗

PubMed2000

Microtubule-dependent formation of podosomal adhesion structures in primary human macrophages.

Podosomes are unique actin-rich adhesion structures of monocyte-derived cells such as macrophages and osteoclasts. They clearly differ from other substratum-contacting organelles like focal adhesions in morphological and functional regards. Formation of podosomes has been shown to be dependent on the small GTPase CDC42Hs and its effector Wiskott-Aldrich syndrome protein (WASp). In this study, we investigated the functional relation between podosomes and the microtubule system in primary human macrophages. We demonstrate that, in contrast to focal adhesions, assembly of podosomes in macrophages and their monocytic precursors is dependent on an intact microtubule system. In contrast, experiments using Wiskott-Aldrich syndrome (WAS) macrophages indicate that the microtubule system is not reciprocally dependent on podosomes. A potential linker between podosomes and microtubules may be WASp itself, considering that microinjection of the WASp polyproline domain prevents podosome reassembly. This polyproline domain is thought to link WASp to microtubules via CDC42 interacting protein 4 (CIP4). Consistently, macrophages microinjected with CIP4 constructs deficient in either the microtubule- or the WASp-binding domain also fail to reassemble podosomes. In sum, our findings show that microtubules are essential for podosome formation in primary human macrophages and that WASp and CIP4 may be involved in this phenomenon.

Actin Cytoskeleton↗

PubMed2005

[Molecular pathogenesis of Wiskott-Aldrich syndrome].

The Wiskott-Aldrich syndrome (WAS) is an X-linked primary immunodeficiency caused by mutations in the gene encoding the WAS protein (WASP). WASP is predominantly expressed in hematopoietic cells and regulates the reorganization of the actin cytoskeleton in response to various important cell stimuli including T cell receptor signaling. WASP is localized at the immunological synapses between T cells and antigen presenting cells, NK cells and target cells. Here we focus on recent basic and clinical research advances for WAS, which has given great insight into the relevance of WASP, its related molecules and its interacting proteins to basic cell biology, actin cytoskeleton, immunological defects and prediction of clinical outcome in WAS patients. In particular, we have reported the significance of WIP (WASP-interacting protein) for molecular regulation of WASP. In addition, we discuss recent basic approaches to gene therapy for WAS.

Humans↗

PubMed2004

Differential roles for Wiskott-Aldrich syndrome protein in immune synapse formation and IL-2 production.

Wiskott-Aldrich syndrome protein (WASP)-deficient T cells exhibit defects in IL-2 production that are widely believed to stem from primary defects in actin remodeling and immune synapse formation. Surprisingly, however, we find that WASP-deficient T cells responding to Ag-specific APCs polymerize actin and organize talin and PKC theta normally, forming an immune synapse that is stable for at least 3 h. At low doses of peptide, WASP-deficient T cells show less efficient talin and PKC theta polarization. Thus, although WASP may facilitate immune synapse formation at low peptide concentrations, WASP is not required for this process. Defects in IL-2 production are observed even under conditions in which immune synapse formation proceeds normally, suggesting that the role of WASP in regulating IL-2 production is independent of its role in immune synapse formation.

Actins↗

PubMed2003

Hymenoptera sting anaphylactic reactions in the Mediterranean population of Albania.

BACKGROUND: Relatively few studies have examined the relation of different hymenoptera sting reactions. OBJECTIVE: To investigate the relation of anaphylactic reactions against stings of different hymenoptera subspecies in the Mediterranean population of Albania. MATERIALS AND METHODS: A retrospective study was conducted using the clinic files of 111 patients who were diagnosed for hymenoptera sting reactions from 1987 to 1996. Antigens used consisted of purified hymenoptera venom (bee, wasp, and paperwasp). The patients were diagnosed by intracutaneous tests in concentrations of 0.001 microgram/ml, 0.01 microgram/ml, 0.1 microgram/ml, and 1 microgram/ml. RESULTS: The median age of the patients was 27 years. 57% of stings occurred between 20 to 40 years of age. The majority of anaphylactic reactions were recorded during the months of June to October, 81% of the patients were admitted to the hospital due to Mueller grade II to III reactions. In 26% of all cases, crossreactions (bee-wasp 16%, bee-wasp-paperwasp 7%, wasp-paperwasp 2%, bee-paperwasp 1%) were found. Of all anaphylactic reactions, 64% were attributed to bees, 24% to wasps, 8% to both bees and wasps, and 2% to paperwasps. CONCLUSIONS: In contrast to industrialized countries such as the United States or Western Europe where urban populations predominate, reactions to bee venom were more prevalent in the present study population.

Adolescent↗

PubMed1994

Isolation, cloning, and characterization of new chitinase stored in active form in chitin-lined venom reservoir.

A 52-kDa protein was purified from the venom gland of an endoparasitic wasp Chelonus sp. near curvimaculatus. The acidic protein (pl 4.8-5.0) was purified, and the NH2-terminal amino acid sequence was determined by direct protein sequencing. A vector-anchored primer and a degenerate primer derived from an 8-amino acid region of the NH2 terminus were used in anchored polymerase chain reaction to generate a probe for screening a cDNA library prepared from mRNA from the venom gland of this wasp. A positive clone of 1596 nucleotides was isolated, sequenced, and found to contain an open reading frame encoding a protein of 483 amino acids. The amino acid sequence encoded in the cDNA clone at the amino terminus was identical to the sequence determined from the purified 52-kDa protein. Comparison of the inferred protein sequence against all of the sequences in the GenBank data base revealed a high degree of similarity to a 62-kDa insect chitinase that is expressed at each molt for the purpose of digesting the chitinous insect cuticle. Two regions that are conserved in a group of chitinases from insects, bacteria and fungi, were also conserved in the wasp 52-kDa protein. The region between amino acid residues 382 and 464 in the 52-kDa wasp chitinase markedly differed in primary sequence from the corresponding region in the 62-kDa insect chitinase, although this region in both the proteins is predicted to have a similar secondary structure predominantly of coils and turns. This region may impart unique structural properties to the 52-kDa chitinase that enables it to exist in an active form in a chitin-lined reservoir without exerting an autotoxic effect to digest the cuticular storage reservoir. Chitinolytic activity occurring in the total venom gland extract was kinetically indistinguishable from that observed for the purified 52-kDa protein, including the substrate concentrations at which maximal velocity and substrate inhibition were reached. The kinetic properties of the 52-kDa wasp chitinase were quite distinct from Serratia marcescens chitinase for both catalytic rate and substrate inhibition.

Amino Acid Sequence↗

PubMed2006

Selectivity of pesticides used on cotton (Gossypium hirsutum) to Trichogramma pretiosum reared on two laboratory-reared hosts.

The side-effects of pesticides (insecticides, fungicides, herbicides and plant growth regulators) used on cotton were tested on adults and pupae of Trichogramma pretiosum Riley reared in the laboratory on two different hosts, the Angoumois grain moth (Sitotroga cerealella Olivier) and the Mediterranean flour moth (Ephestia kuehniella (Zeller)). The eggs of the host enclosing the parasitoid pupae received direct pesticide sprays, while the adults of the parasitoid were exposed to the pesticides through contact with residues on sprayed eggs offered to parasitism. Alpha-cypermethrin, carbosulfan, deltamethrin, endosulfan, profenofos and zeta-cypermethrin were highly noxious to the parasitoid, significantly reducing the percentage of emergence and parasitism of T. pretiosum developing in E. kuehniella or S. cerealella eggs. However, the pupal stage of the parasitoid developing in S. cerealella eggs was less susceptible to alpha-cypermethrin and deltamethrin. Lufenuron and metamidophos greatly reduced the percentage of adult emergence from eggs of both hosts, while novaluron only interfered on this variable when the wasps were developing in E. kuehniella eggs. However, lufenuron and monocrotophos had no effect on the parasitoid pupae of T. pretiosum developing in E. kuehniella eggs. Chlorfluazuron, diafenthiuron, diflubenzuron, fentin hydroxide, mepiquat chloride, novaluron, thiacloprid and triflumuron did not affect T. pretiosum emergence when eggs of S. cerealella enclosing pupae of the wasps were surface treated. The pesticides azoxystrobin, carbendazin + thiram, mepiquat chloride and novaluron had no effect on the ability of the wasps to parasitise E. kuehniella eggs. However, only mepiquat chloride did not affect the percentage of F1 wasps emerging from E. kuehniella eggs. The remaining pesticides moderately reduced the percentage of emergence and parasitism of the wasps when they had contact with the chemicals during their pupal or adult stage. Thus there were differences in pesticide toxicity according to the host used for parasitoid development. These differences were hypothesised to occur because of differences in egg morphology and parasitoid performance.

Animals↗