SCAR knockouts in Dictyostelium: WASP assumes SCAR's position and upstream regulators in pseudopods.

Abstract

Under normal conditions, the Arp2/3 complex activator SCAR/WAVE controls actin polymerization in pseudopods, whereas Wiskott-Aldrich syndrome protein (WASP) assembles actin at clathrin-coated pits. We show that, unexpectedly, Dictyostelium discoideum SCAR knockouts could still spread, migrate, and chemotax using pseudopods driven by the Arp2/3 complex. In the absence of SCAR, some WASP relocated from the coated pits to the leading edge, where it behaved with similar dynamics to normal SCAR, forming split pseudopods and traveling waves. Pseudopods colocalized with active Rac, whether driven by WASP or SCAR, though Rac was activated to a higher level in SCAR mutants. Members of the SCAR regulatory complex, in particular PIR121, were not required for WASP regulation. We thus show that WASP is able to respond to all core upstream signals and that regulators coupled through the other members of SCAR's regulatory complex are not essential for pseudopod formation. We conclude that WASP and SCAR can regulate pseudopod actin using similar mechanisms.

• Authors: Douwe M Veltman, Jason S King, Laura M Machesky, Robert H Insall
• Journal: The Journal of cell biology (J Cell Biol) Vol. 198 Issue 4 Pg. 501-8 (Aug 20 2012) ISSN: 1540-8140 [Electronic] United States
• PMID: 22891261 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Actins
• Multiprotein Complexes
• Protozoan Proteins
• SCAR protein, Dictyostelium
• Wiskott-Aldrich Syndrome Protein

Topics

• Actins (physiology)
• Cell Movement (physiology)
• Chemotaxis (physiology)
• Coated Pits, Cell-Membrane (physiology)
• Dictyostelium (genetics, physiology)
• Gene Knockout Techniques (methods)
• Multiprotein Complexes (deficiency, genetics, metabolism)
• Protozoan Proteins (genetics, metabolism)
• Pseudopodia (physiology)
• Wiskott-Aldrich Syndrome Protein (physiology)