Cysteine-rich protein 1 (CRP1) regulates actin filament bundling

Thuan C Tran , CoreyAyne Singleton , Tamara S Fraley and Jeffrey A Greenwood

Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331, USA

author email corresponding author email

BMC Cell Biology 2005, 6:45doi:10.1186/1471-2121-6-45


Published:	8 December 2005

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 α-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 α-actinin, CRP1 was found to stabilize the interaction of α-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 α-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.

Conclusion

CRP1 regulates actin filament bundling by directly cross-linking actin filaments and stabilizing the interaction of α-actinin with actin filament bundles.