WASP-interacting protein is important for actin filament elongation and prompt pseudopod formation in response to a dynamic chemoattractant gradient.
The role of WASP-interacting protein (WIP) in the process of F-actin assembly during chemotaxis of Dictyostelium was examined. Mutations of the WH1 domain of WASP led to a reduction in binding to WIPa, a newly identified homolog of mammalian WIP, a reduction of F-actin polymerization at the leading edge, and a reduction in chemotactic efficiency. WIPa localizes to sites of new pseudopod protrusion and colocalizes with WASP at the leading edge. WIPa increases F-actin elongation in vivo and in vitro in a WASP-dependent manner. WIPa translocates to the cortical membrane upon uniform cAMP stimulation in a time course that parallels F-actin polymerization. WIPa-overexpressing cells exhibit multiple microspike formation and defects in chemotactic efficiency due to frequent changes of direction. Reduced expression of WIPa by expressing a hairpin WIPa (hp WIPa) construct resulted in more polarized cells that exhibit a delayed response to a new chemoattractant source due to delayed extension of pseudopod toward the new gradient. These results suggest that WIPa is required for new pseudopod protrusion and prompt reorientation of cells toward a new gradient by initiating localized bursts of actin polymerization and/or elongation.
Myers
Scott A
SA
Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN 37232-6600, USA.
Leeper
Laura R
LR
Chung
Chang Y
CY
D008841:Actin Cytoskeleton / Q000502:physiology*; D000199:Actins / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002352:Carrier Proteins / Q000235:genetics / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D002630:Chemotactic Factors / Q000494:pharmacology*; D002633:Chemotaxis; D000242:Cyclic AMP / Q000494:pharmacology; D003598:Cytoskeletal Proteins; D004023:Dictyostelium / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D047908:Intracellular Signaling Peptides and Proteins; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary / Q000235:genetics; D021381:Protein Transport; D015800:Protozoan Proteins / Q000235:genetics / Q000502:physiology*; D011554:Pseudopodia / Q000502:physiology*; D017386:Sequence Homology, Amino Acid
D000199:Actins; D002352:Carrier Proteins; D002630:Chemotactic Factors; D003598:Cytoskeletal Proteins; D047908:Intracellular Signaling Peptides and Proteins; D015800:Protozoan Proteins; C109903:WIPF1 protein, human; D000242:Cyclic AMP