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  • Neuronal Wiskott-Aldrich syndrome protein (N-WASP) is critical for formation of α-smooth muscle actin filaments during myofibroblast differentiation. 22886502

    Myofibroblasts are implicated in pathological stromal responses associated with lung fibrosis. One prominent phenotypic marker of fully differentiated myofibroblasts is the polymerized, thick cytoplasmic filaments containing newly synthesized α-smooth muscle actin (α-SMA). These α-SMA-containing cytoplasmic filaments are important for myofibroblast contractility during tissue remodeling. However, the molecular mechanisms regulating the formation and maturation of α-SMA-containing filaments have not been defined. This study demonstrates a critical role for neuronal Wiskott-Aldrich syndrome protein (N-WASP) in regulating the formation of α-SMA-containing cytoplasmic filaments during myofibroblast differentiation and in myofibroblast contractility. Focal adhesion kinase (FAK) is activated by transforming growth factor-β1 (TGF-β1) and is required for phosphorylation of tyrosine residue 256 (Y256) of N-WASP. Phosphorylation of Y256 of N-WASP is essential for TGF-β1-induced formation of α-SMA-containing cytoplasmic filaments in primary human lung fibroblasts. In addition, we demonstrate that actin-related protein (Arp) 2/3 complex is downstream of N-WASP and mediates the maturation of α-SMA-containing cytoplasmic filaments. Together, this study supports a critical role of N-WASP in integrating FAK and Arp2/3 signaling to mediate formation of α-SMA-containing cytoplasmic filaments during myofibroblast differentiation and maturation.
    Document Type:
    Reference
    Product Catalog Number:
    05-537
    Product Catalog Name:
    Anti-FAK Antibody, clone 4.47

  • Wiskott-Aldrich syndrome protein (WASp) is a binding partner for c-Src family protein-tyrosine kinases. 8805332

    BACKGROUND. Receptor-mediated signal transduction requires the assembly of multimeric complexes of signalling proteins, and a number of conserved protein domains, such as the SH2, SH3 and PH domains, are involved in mediating protein-protein interactions in such complexes. The identification of binding partners for these domains has added considerably to our understanding of signal-transduction pathways, and the purpose of this work was to identify SH3-binding proteins in haematopoietic cells. RESULTS. We performed affinity-chromatography experiments with a panel of GST-SH3 fusion proteins (composed of glutathione-S-transferase appended to various SH3 domains) to search for SH3-binding proteins in a human megakaryocytic cell line. Protein microsequencing identified one of the SH3-binding proteins as WASp, the protein that is defective in Wiskott-Aldrich syndrome (WAS) and isolated X-linked thrombocytopenia. WASp bound preferentially in vitro to SH3 domains from c-Src family kinases, and analysis of proteins expressed in insect cells using a baculovirus vector demonstrated a specific interaction between WASp and the Fyn protein-tyrosine kinase. Finally, in vivo experiments showed that WASp and Fyn physically associate in human haematopoietic cells. CONCLUSIONS. Haematopoietic cells from individuals with WAS exhibit defects in cell morphology and signal transduction, including reduced proliferation and tyrosine phosphorylation in response to stimulatory factors. Members of the c Src family of protein-tyrosine kinases, including Fyn, are involved in a range of signalling pathways - such as those regulating cytoskeletal structure - in both haematopoietic and non-haematopoietic cells. Our data suggest that binding of Fyn to WASp may be a critical event in such signalling pathways in haematopoietic cells.
    Document Type:
    Reference
    Product Catalog Number:
    06-754

  • The Wiskott-Aldrich syndrome protein (WASP): roles in signaling and cytoskeletal organization. 10358777

    The Wiskott-Aldrich Syndrome (WAS) is a rare X-linked primary immunodeficiency that is characterized by recurrent infections, hematopoietic malignancies, eczema, and thrombocytopenia. A variety of hematopoietic cells are affected by the genetic defect, including lymphocytes, neutrophils, monocytes, and platelets. Early studies noted both signaling and cytoskeletal abnormalities in lymphocytes from WAS patients. Following the identification of WASP, the gene mutated in patients with this syndrome, and the more generally expressed WASP homologue N-WASP, studies have demonstrated that WASP-family molecules associate with numerous signaling molecules known to alter the actin cytoskeleton. WASP/N-WASP may depolymerize actin directly and/or serve as an adaptor or scaffold for these signaling molecules in a complex cascade that regulates the cytoskeleton.
    Document Type:
    Reference
    Product Catalog Number:
    07-066

  • Scar1 and the related Wiskott-Aldrich syndrome protein, WASP, regulate the actin cytoskeleton through the Arp2/3 complex. 9889097

    BACKGROUND: The actin-related proteins Arp2 and Arp3 are part of a seven-protein complex which is localized in the lamellipodia of a variety of cell types, and in actin-rich spots of unknown function. The Arp2/3 complex enhances actin nucleation and causes branching and crosslinking of actin filaments in vitro; in vivo it is thought to drive the formation of lamellipodia and to be a control center for actin-based motility. The Wiskott-Aldrich syndrome protein, WASP, is an adaptor protein implicated in the transmission of signals from tyrosine kinase receptors and small GTPases to the actin cytoskeleton. Scar1 is a member of a new family of proteins related to WASP, and it may also have a role in regulating the actin cytoskeleton. Scar1 is the human homologue of Dictyostelium Scar1, which is thought to connect G-protein-coupled receptors to the actin cytoskeleton. The mammalian Scar family contains at least four members. We have examined the relationships between WASP, Scar1, and the Arp2/3 complex. RESULTS: We have identified WASP and its relative Scar1 as proteins that interact with the Arp2/3 complex. We have used deletion analysis to show that both WASP and Scar1 interact with the p21 subunit of the Arp2/3 complex through their carboxyl termini. Overexpression of carboxy-terminal fragments of Scar1 or WASP in cells caused a disruption in the localization of the Arp2/3 complex and, concomitantly, induced a complete loss of lamellipodia and actin spots. The induction of lamellipodia by platelet-derived growth factor was also suppressed by overexpression of the fragment of Scar1 that binds to the Arp2/3 complex. CONCLUSIONS: We have identified a conserved sequence domain in proteins of the WASP family that binds to the Arp2/3 complex. Overexpression of this domain in cells disrupts the localization of the Arp2/3 complex and inhibits lamellipodia formation. Our data suggest that WASP-related proteins may regulate the actin cytoskeleton through the Arp2/3 complex.
    Document Type:
    Reference
    Product Catalog Number:
    07-410
    Product Catalog Name:

  • 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). 12591280

    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.
    Document Type:
    Reference
    Product Catalog Number:
    06-182

  • Identification of WASP mutations in patients with Wiskott-Aldrich syndrome and isolated thrombocytopenia reveals allelic heterogeneity at the WAS locus. 8528198

    Mutation in the gene encoding the recently isolated WASP protein has now been identified as the genetic defect responsible for the X-linked Wiskott-Aldrich syndrome (WAS), a primary immunodeficiency disease associated with extensive phenotypic variability. To elucidate the range of WASP mutations responsible for WAS, we used PCR-SSCP analysis to screen for WASP gene mutation in 19 unrelated boys with the diagnosis of classical or attenuated WAS or isolated thrombocytopenia. All 19 patients had WASP mutations, each of which localized to the initial three or terminal three exons of the gene, and the majority of which were unique in each case. However, a missense mutation which results in substitution of the arginine at WAS codon 86 was identified in three boys with severe WAS as well as in one boy presenting with thrombocytopenia alone. While the three mutations found in the isolated thrombocytopenia patients leave the reading frame intact, about one-half of the gene alterations detected in both severe and attenuated WAS patients result in frameshifted transcript and premature translation termination. These findings therefore confirm the association of WAS with WASP mutation and identify WASP mutation as a cause for isolated congenital thrombocytopenia in males. While the WASP gene defects responsible for isolated thrombocytopenia and other mild presentations of WAS do not appear distinct from those resulting in severe WAS, these data indicate that analysis of WASP gene mutation provides a valuable tool for distinguishing the spectrum of WAS patients and the subset of males with isolated thrombocytopenia who represent mild cases of WAS.
    Document Type:
    Reference
    Product Catalog Number:
    06-754

  • Abelson interactor 1 (ABI1) and its interaction with Wiskott-Aldrich syndrome protein (wasp) are critical for proper eye formation in Xenopus embryos. 23558677

    Abl interactor 1 (Abi1) is a scaffold protein that plays a central role in the regulation of actin cytoskeleton dynamics as a constituent of several key protein complexes, and homozygous loss of this protein leads to embryonic lethality in mice. Because this scaffold protein has been shown in cultured cells to be a critical component of pathways controlling cell migration and actin regulation at cell-cell contacts, we were interested to investigate the in vivo role of Abi1 in morphogenesis during the development of Xenopus embryos. Using morpholino-mediated translation inhibition, we demonstrate that knockdown of Abi1 in the whole embryo, or specifically in eye field progenitor cells, leads to disruption of eye morphogenesis. Moreover, signaling through the Src homology 3 domain of Abi1 is critical for proper movement of retinal progenitor cells into the eye field and their appropriate differentiation, and this process is dependent upon an interaction with the nucleation-promoting factor Wasp (Wiskott-Aldrich syndrome protein). Collectively, our data demonstrate that the Abi1 scaffold protein is an essential regulator of cell movement processes required for normal eye development in Xenopus embryos and specifically requires an Src homology 3 domain-dependent interaction with Wasp to regulate this complex morphogenetic process.
    Document Type:
    Reference
    Product Catalog Number:
    Multiple
    Product Catalog Name:
    Multiple

  • Studies of the expression of the Wiskott-Aldrich syndrome protein. 8647957

    The Wiskott-Aldrich syndrome (WAS) is an X-linked disorder characterized by thrombocytopenia, eczema, disorders in cell-mediated and humoral immunity, and a proclivity to lymphoproliferative disease. The gene responsible encodes a 53-kD proline-rich protein of unknown function (WASP). We produced a FLAG-WASP fusion protein that was used to immunize mice and produce mAbs against WASP. Using monoclonal anti-WASP in Western immunoblots, we have determined that WASP is present in the cytoplasmic but not nuclear fraction of normal human peripheral blood mononuclear cells, in normal human platelets, in T lymphocytes, non-T lymphocytes, and monocytes. The protein is produced in the B cell immunoblastic cell line DS-1, in normal EBV-transformed B cell lines, and in HEL92.1.7, but is barely detectable in MOLT-4 and not detectable in K562. WASP was present in two of four EBV-transformed cell lines from WAS patients. Splenic tissue immunostaining was performed in two patients, and the results correlated with the results of the Western blots. Sequence analysis of WASP cDNA from two patients who produce WASP show mutations causing amino acid substitutions. These studies establish a foundation for further studies aimed at understanding the function of WASP.
    Document Type:
    Reference
    Product Catalog Number:
    06-754

  • Platelet actin nodules are podosome-like structures dependent on Wiskott-Aldrich syndrome protein and ARP2/3 complex. 26028144

    The actin nodule is a novel F-actin structure present in platelets during early spreading. However, only limited detail is known regarding nodule organization and function. Here we use electron microscopy, SIM and dSTORM super-resolution, and live-cell TIRF microscopy to characterize the structural organization and signalling pathways associated with nodule formation. Nodules are composed of up to four actin-rich structures linked together by actin bundles. They are enriched in the adhesion-related proteins talin and vinculin, have a central core of tyrosine phosphorylated proteins and are depleted of integrins at the plasma membrane. Nodule formation is dependent on Wiskott-Aldrich syndrome protein (WASp) and the ARP2/3 complex. WASp(-/-) mouse blood displays impaired platelet aggregate formation at arteriolar shear rates. We propose actin nodules are platelet podosome-related structures required for platelet-platelet interaction and their absence contributes to the bleeding diathesis of Wiskott-Aldrich syndrome.
    Document Type:
    Reference
    Product Catalog Number:
    Multiple
    Product Catalog Name:
    Multiple