WASP gene mutations in Wiskott-Aldrich syndrome and X-linked thrombocytopenia

Derry, Jonathan M.J.; Kerns, Julie A.; Weinberg, Kenneth I.; Ochs, Hans D.; Volpini, Vı́ctor; Estivill, Xavier; Walker, Ann P.; Francke, Uta

doi:10.1093/hmg/4.7.1127

Cited by 141 publications

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“…The R477K (R478K in N-WASP) mutation is found in patients with Wiskott-Aldrich syndrome and reduces WASP-mediated activation of the Arp2/3 complex (Fig. 6B) (9,40). This mutation decreased cross-linking by ∼2.5-fold at saturation compared with wild-type N-WASP, demonstrating the importance of this residue in stimulating the short-pitch switch ( Fig.…”

Section: Resultsmentioning

confidence: 91%

Role and structural mechanism of WASP-triggered conformational changes in branched actin filament nucleation by Arp2/3 complex

Rodnick-Smith

Luan

Liu

et al. 2016

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

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The Arp2/3 (Actin-related proteins 2/3) complex is activated by WASP (Wiskott-Aldrich syndrome protein) family proteins to nucleate branched actin filaments that are important for cellular motility. WASP recruits actin monomers to the complex and stimulates movement of Arp2 and Arp3 into a "short-pitch" conformation that mimics the arrangement of actin subunits within filaments. The relative contribution of these functions in Arp2/3 complex activation and the mechanism by which WASP stimulates the conformational change have been unknown. We purified budding yeast Arp2/3 complex held in or near the short-pitch conformation by an engineered covalent cross-link to determine if the WASP-induced conformational change is sufficient for activity. Remarkably, cross-linked Arp2/3 complex bypasses the need for WASP in activation and is more active than WASP-activated Arp2/3 complex. These data indicate that stimulation of the short-pitch conformation is the critical activating function of WASP and that monomer delivery is not a fundamental requirement for nucleation but is a specific requirement for WASP-mediated activation. During activation, WASP limits nucleation rates by releasing slowly from nascent branches. The cross-linked complex is inhibited by WASP's CA region, even though CA potently stimulates cross-linking, suggesting that slow WASP detachment masks the activating potential of the short-pitch conformational switch. We use structure-based mutations and WASP-Arp fusion chimeras to determine how WASP stimulates movement toward the short-pitch conformation. Our data indicate that WASP displaces the autoinhibitory Arp3 C-terminal tail from a hydrophobic groove at Arp3′s barbed end to destabilize the inactive state, providing a mechanism by which WASP stimulates the short-pitch conformation and activates Arp2/3 complex.actin | Arp2/3 | WASP

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Section: Resultsmentioning

confidence: 91%

Role and structural mechanism of WASP-triggered conformational changes in branched actin filament nucleation by Arp2/3 complex

Rodnick-Smith

Luan

Liu

et al. 2016

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

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“…The most common forms of macrothrombocytopenia, that is, Bernard-Soulier syndrome and MYH9 disorders, were first excluded by flow cytometry for platelet glycoprotein Ib/IX and immunofluorescence analysis of granulocyte myosin IIA localization, respectively. 16 Mutation screening of the known candidate genes for X-linked thrombocytopenia such as WAS 21,22 and GATA1 23 excluded the presence of mutations in the patient (data not shown). We hypothesized that the macrothrombocytopenia in the present patient was caused by the mutation of an unknown gene on chromosome X.…”

Section: Resultsmentioning

confidence: 99%

FLNA p.V528M substitution is neither associated with bilateral periventricular nodular heterotopia nor with macrothrombocytopenia

et al. 2010

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Filamin A is encoded by the FLNA gene on chromosome Xq28 and functions in cross-linking actin filaments into orthogonal networks in the cortical cytoplasm. FLNA p.V528M was initially detected in a female autopsy case of X-linked bilateral periventricular nodular heterotopia (BPNH), a neuronal migration disorder characterized by subependymal nodules of gray matter. During our mutation analysis of FLNA in a boy with apparent X-linked thrombocytopenia, we detected the p.V528M variant. The patient, mother and sister, who were heterozygous for the substitution, did not have BPNH. We observed an allele frequency of 4.8% in healthy control Japanese, but did not observe the variant in Caucasian subjects. Hemizygous controls had a normal platelet count and size. We suggest that p.V528M is neither associated with BPNH nor with thrombocytopenia and giant platelets, and represents a functional polymorphism.

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“…In cofilin homology domain, there is a part that consists of four amino acid residues from Lys-473 to Lys-476 and that is abundant in basicity. In some Wiskott-Aldrich syndrome patients, muta- tions at the basic amino acid residues among the four residues are also found (26,27). These findings suggest that the four amino acid residues are indispensable to the function of N-WASP.…”

Section: Construction Of Cofilin Homology Domain Mutant (⌬Cof N-wasp)mentioning

confidence: 99%

Essential Role of Neural Wiskott-Aldrich Syndrome Protein in Neurite Extension in PC12 Cells and Rat Hippocampal Primary Culture Cells

Banzai

Miki

Yamaguchi

et al. 2000

Journal of Biological Chemistry

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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 (⌬cof) 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 ⌬cof N-WASP suppressed neurite extension of PC12 cells. In support of this, the VCA region of ⌬cof 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-⌬cof double mutant has no significant dominant negative effect. Finally, the expression of the ⌬cof 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.The actin cytoskeleton plays a critical role in the regulation of cellular morphological change in response to various external stimuli (1, 2). In the case of neural development, actin filaments have been shown to accumulate at the growth cone (3), a guidance apparatus located at the tip of growing neurites. It has long been suggested that the actin cytoskeletal reorganization at growth cones including filopodium and lammelipodium formation is the key determinant of the direction and/or speed of neurite extension. Thus, clarification of the regulatory mechanism behind the reorganization of the actin cytoskeleton in neurons will ultimately lead to a better understanding of neural development.Evidence has been accumulating that Rho family small GTPases regulate the reorganization of the actin cytoskeleton (4). Indeed, two family members, Cdc42 and Rac, are shown to induce filopodium and lammelipodium formations, respectively (5-7). Furthermore, recent reports demonstrated that their function is essential for neurite extension in 9). However, the target proteins that function in neurite extension in neurons have yet to be identified.We found N-WASP as a 65-kDa protein that binds to the SH3 domains of Ash/Grb2 adaptor protein (10). N-WASP possesses a GBD/CRIB motif through which N-WASP directly binds to activated Cdc42 (11). In addition, N-WASP can induce filopodium formation downstream of Cdc42 in COS 7 cells (11). We have also shown that verprolin homology domain (V), which is an actin-binding site, is essential for filopo...

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WASP gene mutations in Wiskott-Aldrich syndrome and X-linked thrombocytopenia

Cited by 141 publications

References 0 publications

Role and structural mechanism of WASP-triggered conformational changes in branched actin filament nucleation by Arp2/3 complex

Role and structural mechanism of WASP-triggered conformational changes in branched actin filament nucleation by Arp2/3 complex

FLNA p.V528M substitution is neither associated with bilateral periventricular nodular heterotopia nor with macrothrombocytopenia

Essential Role of Neural Wiskott-Aldrich Syndrome Protein in Neurite Extension in PC12 Cells and Rat Hippocampal Primary Culture Cells

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