- BSc, MSc, PhD (IMCB, National University of Singapore)
- Postdoctoral Fellow at IMCB, Singapore
- Research Associate at U. of Cambridge (UK)
- Research Fellow IMA, Singapore
My laboratory is interested in characterizing the role of WASP and N-WASP in cellular processes such as cell proliferation and migration. Wiskott Aldrich Syndrome (WAS) is an immunodeficiency disorder characterized by recurrent bacterial infection, thrombocytopenia and eczema. The WAS protein (WASP) is an adaptor protein involved in the regulation of actin cytoskeleton by activating of the Arp2/3 complex. WASP is expressed predominantly in hematopoietic cells while its homologue, N-WASP (neural) is expressed ubiquitously. A number of proteins including the three mammalian verprolins, WIP (WASP Interacting Protein), WIRE (WIP-RElated) and CR16 (Corticoid Regulated) have been shown to interact with WASP and N-WASP. We are presently characterizing the role of N-WASP and its interacting proteins in tumorigenesis, epithelial-to-mesenchymal transition, metastasis and wound healing.
WASP is required for proliferation of T-cell upon activation and for polarization of the actin cytoskeleton. A number of mutations in WASP which causes the disease have been identified from clinical samples but the molecular defects caused by these mutations have not been identified. In order to characterize these mutants we have generated Jurkat T-cells with the expression of WASP knocked down using shRNA (JurkatWKD T-cells). JurkatWKD T-cells have defect in cell migration towards SDF-1a, T-cell proliferation and IL-2 secretion upon activation by CD3/CD28.
WT Jurkat T-cells
WASPKD Jurkat T-cells
Expression of wild type WASP in JurkatWKDT-cells rescues all the defects and thus the JurkatWKD T-cells are being used to characterize the molecular defect of the WASP mutants causing Wiskott Aldrich Syndrome, X-Linked thrombocytopenia and X-linked Neutropenia.
N-WASP is expressed ubiquitously and a number of proteins have been shown to activate N-WASP in in-vitro actin polymerization assay. We have shown that N-WASP is crucial for cell-ecm adhesion as N-WASP-/-mouse fibroblast adhere poorly to fibronectin compared to N-WASP+/+ mouse fibroblast cells.
During metastasis the cancer cells undergo epithelial to mesenchymal transition (EMT) which aids in the spread of tumors. EMT involves changes in cell-ecm, cell-cell adhesion and cell motility. We have shown that the expression of N-WASP is upregulated during EMT and are currently characterizing the role of N-WASP and N-WASP binding proteins in EMT and Metastasis.
Lamellipodia and Filopodia are actin rich structures which play critical role in cell migration and N-WASP has been shown to be critical for filopodia formation. We have shown the WIRE can induce filopodia in concert with IRSp53 and subsequently showed that IRSp53 negatively regulated the formation of Muscle.
Conformational analysis of WASP and N-WASP
Both WASP and N-WASP has been suggested to adopt a closed conformation through intramolecular interaction between the C-terminal acidic domain and the Basic region next to the GTPase binding domain. In order to characterize the conformational changes we have adopted the Bimolecular Fluorescence Complementation (BiFC) assay. We fused the N-terminal half of Yellow Fluorescent Protein to the N-terminal of WASP and the C-terminal half of Yellow Fluorescent Protein to the C-terminal of WASP, to generate the WASPsensor molecule. We detect fluorescence when WASP is in the close conformation and fluorescence is reduced when WASP adopts an open conformation.