title: Mechanism of calponin stabilization of cross-linked actin networks.
abstract: The actin-binding protein calponin has been previously implicated in actin cytoskeletal regulation and is thought to act as an actin stabilizer, but the mechanism of its function is poorly understood. To investigate this underlying physical mechanism, we studied an in vitro model system of cross-linked actin using bulk rheology. Networks with basic calponin exhibited a delayed onset of strain stiffening (10.0% without calponin, 14.9% with calponin) and were able to withstand a higher maximal strain before failing (35% without calponin, 56% with calponin). Using fluorescence microscopy to study the mechanics of single actin filaments, we found that calponin increased the flexibility of actin filaments, evident as a decrease in persistence length from 17.6 μm without to 7.7 μm with calponin. Our data are consistent with current models of affine strain behavior in semiflexible polymer networks, and suggest that calponin stabilization of actin networks can be explained purely by changes in single-filament mechanics. We propose a model in which calponin stabilizes actin networks against shear through a reduction of persistence length of individual filaments.
authors.affiliation: Department of Physiology and Biophysics, Boston University, Boston, Massachusetts; School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts.
authors.forename: Mikkel Herholdt
authors.initials: MH
authors.lastname: Jensen
authors.affiliation: School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts.
authors.forename: Eliza J
authors.initials: EJ
authors.lastname: Morris
authors.affiliation: Department of Health Sciences, Boston University, Boston, Massachusetts.
authors.forename: Cynthia M
authors.initials: CM
authors.lastname: Gallant
authors.affiliation: Department of Health Sciences, Boston University, Boston, Massachusetts.
authors.forename: Kathleen G
authors.initials: KG
authors.lastname: Morgan
authors.affiliation: School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts.
authors.forename: David A
authors.initials: DA
authors.lastname: Weitz
authors.affiliation: Department of Physiology and Biophysics, Boston University, Boston, Massachusetts. Electronic address: jxmoore@bu.edu.
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Moore
mesh_terms: D008841:Actin Cytoskeleton / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D004548:Elasticity; D006801:Humans; D008840:Microfilament Proteins / Q000737:chemistry / Q000378:metabolism*; D008954:Models, Biological; D055550:Protein Stability; D011817:Rabbits; D000096985:Calponins
chemical_list: D002135:Calcium-Binding Proteins; D008840:Microfilament Proteins; D000096985:Calponins