The N-terminus of Dictyostelium Scar interacts with Abi and HSPC300 and is essential for proper regulation and function.
Scar/WAVE proteins, members of the conserved Wiskott-Aldrich syndrome (WAS) family, promote actin polymerization by activating the Arp2/3 complex. A number of proteins, including a complex containing Nap1, PIR121, Abi1/2, and HSPC300, interact with Scar/WAVE, though the role of this complex in regulating Scar function remains unclear. Here we identify a short N-terminal region of Dictyostelium Scar that is necessary and sufficient for interaction with HSPC300 and Abi in vitro. Cells expressing Scar lacking this N-terminal region show abnormalities in F-actin distribution, cell morphology, movement, and cytokinesis. This is true even in the presence of wild-type Scar. The data suggest that the first 96 amino acids of Scar are necessary for participation in a large-molecular-weight protein complex, and that this Scar-containing complex is responsible for the proper localization and regulation of Scar. The presence of mis-regulated or unregulated Scar has significant deleterious effects on cells and may explain the need to keep Scar activity tightly controlled in vivo either by assembly in a complex or by rapid degradation.
Caracino
Diana
D
Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA.
Jones
Cheryl
C
Compton
Mark
M
Saxe
Charles L
CL
D000199:Actins / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D002633:Chemotaxis; D048749:Cytokinesis; D004023:Dictyostelium / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D066298:In Vitro Techniques; D046912:Multiprotein Complexes; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
D000199:Actins; D046912:Multiprotein Complexes; D010446:Peptide Fragments; D015800:Protozoan Proteins; D011993:Recombinant Fusion Proteins; C491975:SCAR protein, Dictyostelium; D049452:Green Fluorescent Proteins