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

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 c...

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Bibliographic Details
Published in:The Journal of cell biology 2012-08, Vol.198 (4), p.501-508
Main Authors: Veltman, Douwe M, King, Jason S, Machesky, Laura M, Insall, Robert H
Format: Article
Language:English
Subjects:
Actins - physiology
Biochemistry
Cell Movement - physiology
Chemotaxis - physiology
Coated Pits, Cell-Membrane - physiology
Dictyostelium - genetics
Dictyostelium - physiology
Gene Knockout Techniques - methods
Multiprotein Complexes - deficiency
Multiprotein Complexes - genetics
Multiprotein Complexes - metabolism
Parasitic protozoa
Polymerization
Proteins
Protozoan Proteins - genetics
Protozoan Proteins - metabolism
Pseudopodia - physiology
Wiskott-Aldrich Syndrome Protein - physiology
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Summary: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.
ISSN:0021-9525
1540-8140
DOI:10.1083/jcb.201205058