Regulation of WASP in Actin Signaling: From Angstroms to Microns
type: CreativeWork
description: Wiskott-Aldrich syndrome protein (WASP) regulates membrane-attached force generation by promoting actin polymerization, which is key to cell motility and immune responses. Mutations in WASP lead to Wiskott-Aldrich syndrome and neutropenia. My graduate research was focused on allosteric regulation of WASP by an Enterohaemorrhagic E. coli (EHEC) effector EspFU. This study leads to novel mechanisms of WASP regulation and also sheds light on how cells conduct μm-scale assembly by orchestrating nm-scale proteins spatially and temporally. EHEC hijacks the host cytoskeleton during infection to form actin-rich ‘pedestals’ beneath the invading bacteria. The multiple repeat-containing effector EspFU stimulates pedestal formation by activating WASP, which is itself autoinhibited through interactions between a regulatory GTPase binding domain (GBD) and an activity bearing VCA region. First, I investigated how a single repeat fragment (1R) from EspFU relieves WASP autoinhibition. By determining the solution structure of a complex between the WASP GBD and 1R, I showed that EspFU binds to WASP by mimicking the C region of the VCA domain. 1R has a higher affinity toward the GBD than does VCA, allowing it to displace the VCA and activate WASP. Next, I examined the role of multiple repeats of EspFU. Surprisingly, a two-repeat fragment is much more potent in stimulating WASP-dependent actin polymerization than a single repeat at the same total repeat concentration. My colleagues and I showed that the inter-repeat cooperativity of EspFU originates from its ability to engage two active WASP molecules. Such dimers have much higher affinity (~100-fold) than monomers for the actin nucleation factor, the Arp2/3 complex. The combined mechanism enables EHEC to dominate the eukaryotic cytoskeletal machinery. These studies culminated in discovery of the hierarchical regulation of WASP proteins: allosteric activators release autoinhibition, and dimerization/oligomerization of active WASP molecul…
abstract: Wiskott-Aldrich syndrome protein (WASP) regulates membrane-attached force generation by promoting actin polymerization, which is key to cell motility and immune responses. Mutations in WASP lead to Wiskott-Aldrich syndrome and neutropenia. My graduate research was focused on allosteric regulation of WASP by an Enterohaemorrhagic E. coli (EHEC) effector EspFU. This study leads to novel mechanisms of WASP regulation and also sheds light on how cells conduct μm-scale assembly by orchestrating nm-scale proteins spatially and temporally. EHEC hijacks the host cytoskeleton during infection to form actin-rich ‘pedestals’ beneath the invading bacteria. The multiple repeat-containing effector EspFU stimulates pedestal formation by activating WASP, which is itself autoinhibited through interactions between a regulatory GTPase binding domain (GBD) and an activity bearing VCA region. First, I investigated how a single repeat fragment (1R) from EspFU relieves WASP autoinhibition. By determining the solution structure of a complex between the WASP GBD and 1R, I showed that EspFU binds to WASP by mimicking the C region of the VCA domain. 1R has a higher affinity toward the GBD than does VCA, allowing it to displace the VCA and activate WASP. Next, I examined the role of multiple repeats of EspFU. Surprisingly, a two-repeat fragment is much more potent in stimulating WASP-dependent actin polymerization than a single repeat at the same total repeat concentration. My colleagues and I showed that the inter-repeat cooperativity of EspFU originates from its ability to engage two active WASP molecules. Such dimers have much higher affinity (~100-fold) than monomers for the actin nucleation factor, the Arp2/3 complex. The combined mechanism enables EHEC to dominate the eukaryotic cytoskeletal machinery. These studies culminated in discovery of the hierarchical regulation of WASP proteins: allosteric activators release autoinhibition, and dimerization/oligomerization of active WASP molecul…
author: Cheng, Hui-Chun
language: en
keywords: Wiskott-Aldrich Syndrome Protein, Escherichia coli Proteins, Carrier Proteins
date published: 2011-08-26T17:34:28Z
date modified: 2026-07-24T05:52:20Z
provider: University of Texas Southwestern Medical Center
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Texas Southwestern Medical Center

PropertyValue
property ID: Handle
value: https://hdl.handle.net/2152.5/878