The Interplay Between SCAR (WAVE) and WASP in Actin-Based Motility

Davidson, A.J., Veltman, D.M., Machesky, L.M. and Insall, R.H. (2012) The Interplay Between SCAR (WAVE) and WASP in Actin-Based Motility. 2012 American Society for Cell Biology Annual Meeting, San Francisco, CA, USA, 15-19 Dec 2012. p. 1823. (doi: 10.1091/mbc.e12-10-0757)

Abstract

The WASP family of proteins recruit and activate the Arp2/3 complex to promote actin polymerization. In particular, WASP family member SCAR (or WAVE) underlies protrusion (or 'pseudopod') extension during cell migration. Although the simple amoeba Dictyostelium discoideum is in many ways an ideal model for the study of cell migration, the limited but undeniable ability of the Dictyostelium scar null to extend pseudopodia and migrate has been a continued source of frustration and contention. Recently our lab has demonstrated that WASP is unexpectedly able to compensate for the loss of SCAR, adopting very different temporal and spatial dynamics compared to its normal behavior in wild-type cells (Veltman, D. M., et al. 2012. J. Cell Biol.) A Dictyostelium wasp knockout has been unobtainable thus far and many people have assumed WASP must be essential for viability. We have now disrupted wasp by homologous recombination both alone and in combination with scar. We first confirmed that WASP is not required for normal cell migration in wild-type cells and instead predominantly localizes to sites of clathrin-mediated endocytosis. When visualized by TIRF microscopy, clathrin internalization is severely impaired in the wasp null and arrested clathrin pits accumulate on the plasma membrane. During cytokinesis, these trapped pits are swept into the forming cleavage furrow, which bulges and often fails to resolve. Our evidence suggests that the defective internalization of coated pits in the wasp null results in an impaired ability of the cell to remodel its plasma membrane, a process necessary for successful cleavage furrow formation and cytokinesis. The loss of either SCAR or WASP alone has negligible effects on growth, however the loss of both has dire consequences. The double scar/wasp null has a severe defect in cell migration and is reminiscent of the recently published Arp2/3 depleted cells in morphology (Wu, C., et al. 2012. Cell & Suraneni, P., et al. 2012. J. Cell Biol.) Having demonstrated that SCAR and WASP are each capable of driving actin-based protrusion and cell migration, we shall present the detailed analysis of cells that lack one or both of these proteins.

• Item Type: Conference or Workshop Item
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Machesky, Professor Laura
• Authors: Davidson, A.J., Veltman, D.M., Machesky, L.M., and Insall, R.H.
• College/School: College of Medical Veterinary and Life Sciences > School of Cancer Sciences
• ISSN: 1939-4586