title: CPI motif interaction is necessary for capping protein function in cells.
abstract: Capping protein (CP) has critical roles in actin assembly in vivo and in vitro. CP binds with high affinity to the barbed end of actin filaments, blocking the addition and loss of actin subunits. Heretofore, models for actin assembly in cells generally assumed that CP is constitutively active, diffusing freely to find and cap barbed ends. However, CP can be regulated by binding of the 'capping protein interaction' (CPI) motif, found in a diverse and otherwise unrelated set of proteins that decreases, but does not abolish, the actin-capping activity of CP and promotes uncapping in biochemical experiments. Here, we report that CP localization and the ability of CP to function in cells requires interaction with a CPI-motif-containing protein. Our discovery shows that cells target and/or modulate the capping activity of CP via CPI motif interactions in order for CP to localize and function in cells.
authors.affiliation: Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, Missouri 63110-1093, USA.
authors.forename: Marc
authors.initials: M
authors.lastname: Edwards
authors.affiliation: Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, Missouri 63110-1093, USA.
authors.forename: Patrick
authors.initials: P
authors.lastname: McConnell
authors.affiliation: Departments of Biology and Cell Biology, University of Virginia, Charlottesville, Virginia 22904-4328, USA.
authors.forename: Dorothy A
authors.initials: DA
authors.lastname: Schafer
authors.affiliation: Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, Missouri 63110-1093, USA.
authors.forename: John A
authors.initials: JA
authors.lastname: Cooper
mesh_terms: D051344:Actin Capping Proteins / Q000235:genetics / Q000378:metabolism*; D000199:Actins / Q000378:metabolism; D020816:Amino Acid Motifs; D000818:Animals; D045744:Cell Line, Tumor; D004926:Escherichia coli; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D009154:Mutation; D034622:RNA Interference
chemical_list: D051344:Actin Capping Proteins; D000199:Actins