title: Cysteine-rich protein 1 (CRP1) regulates actin filament bundling.
abstract: BACKGROUND
  Cysteine-rich protein 1 (CRP1) is a LIM domain containing protein localized to the nucleus and the actin cytoskeleton. CRP1 has been demonstrated to bind the actin-bundling protein alpha-actinin and proposed to modulate the actin cytoskeleton; however, specific regulatory mechanisms have not been identified.
  
  
  RESULTS
  CRP1 expression increased actin bundling in rat embryonic fibroblasts. Although CRP1 did not affect the bundling activity of alpha-actinin, CRP1 was found to stabilize the interaction of alpha-actinin with actin bundles and to directly bundle actin microfilaments. Using confocal and photobleaching fluorescence resonance energy transfer (FRET) microscopy, we demonstrate that there are two populations of CRP1 localized along actin stress fibers, one associated through interaction with alpha-actinin and one that appears to bind the actin filaments directly. Consistent with a role in regulating actin filament cross-linking, CRP1 also localized to the membrane ruffles of spreading and PDGF treated fibroblasts.
  
  
  CONCLUSIONS
  CRP1 regulates actin filament bundling by directly cross-linking actin filaments and stabilizing the interaction of alpha-actinin with actin filament bundles.
authors.affiliation: Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331, USA.
authors.forename: Thuan C
authors.initials: TC
authors.lastname: Tran
authors.forename: CoreyAyne
authors.initials: C
authors.lastname: Singleton
authors.forename: Tamara S
authors.initials: TS
authors.lastname: Fraley
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Greenwood
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism / Q000648:ultrastructure; D000185:Actinin / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D030161:Avian Proteins / Q000235:genetics / Q000502:physiology*; D002352:Carrier Proteins / Q000235:genetics / Q000502:physiology*; D002448:Cell Adhesion; D002462:Cell Membrane / Q000378:metabolism / Q000502:physiology; D002478:Cells, Cultured; D002645:Chickens; D003599:Cytoskeleton; D005347:Fibroblasts / Q000166:cytology; D060588:LIM Domain Proteins; D051381:Rats; D014162:Transfection
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D030161:Avian Proteins; D002352:Carrier Proteins; D060588:LIM Domain Proteins; D000185:Actinin