Author: Cheng Wang, Fei Gao, Yan Lin
Research Article
Cysteine-Rich Protein 1 (CRP1) Facilitates Actin Filament Bundling and Cytoskeletal Structure
Yan Lin¹*, Fei Gao2 and Cheng Wang3
¹Institute of Pathogen Biology, Chinese Academy of Medical Sciences, Beijing, China
²Shanghai Institute of Biochemistry and Cell Biology, Shanghai, China
³Department of Clinical Research, Nanjing Medical University, Nanjing, China
Published: 31 March 2021
Abstract
Background: The actin cytoskeleton is a crucial regulator of cell shape, motility, and mechanical integrity, relying on higher-order structures such as stress fibers and filopodia. These structures are maintained by actin-binding and cross-linking proteins. Cysteine-rich protein 1 (CRP1), a LIM domain-containing protein, localizes to actin-rich sites like stress fibers and focal adhesions. Although CRP1 has been linked to cytoskeletal regulation and mechanotransduction, its direct role in organizing actin filaments has not been fully established.
Objective: To determine whether CRP1 directly interacts with F-actin and contributes to the formation of bundled actin structures, thereby influencing cytoskeletal organization in cells.
Methods: In vitro assays, including co-sedimentation, low-speed centrifugation, and electron microscopy, were used to evaluate direct binding and bundling activity between recombinant CRP1 and F-actin. In parallel, cell-based studies were conducted using CRP1 overexpression and siRNA-mediated knockdown in fibroblasts, followed by fluorescence microscopy to assess changes in actin stress fiber organization and morphology.
Results: CRP1 was shown to bind directly to F-actin and organize it into dense bundles in vitro, with the bundling effect being concentration-dependent. In cells, overexpressed GFP-tagged CRP1 co-localized with thickened stress fibers, whereas CRP1 knockdown led to reduced stress fiber formation and altered cell morphology. These findings indicate a clear correlation between CRP1 expression levels and actin cytoskeletal structure.
Conclusion: CRP1 acts as a direct actin-bundling protein, significantly contributing to the structural organization of F-actin in cells. This function explains its localization to actin-rich structures and supports its role in cellular architecture and mechanotransduction. Understanding CRP1’s activity may offer insight into cytoskeletal regulation during differentiation and tissue-specific functions.
Keywords: Cysteine-rich protein 1 (CRP1); Actin bundling; Actin cytoskeleton; LIM domain; Stress fibers; Focal adhesions; Cytoskeletal organization.
