title: Distributed actin turnover in the lamellipodium and FRAP kinetics.
abstract: Studies of actin dynamics at the leading edge of motile cells with single-molecule speckle (SiMS) microscopy have shown a broad distribution of EGFP-actin speckle lifetimes and indicated actin polymerization and depolymerization over an extended region. Other experiments using FRAP with the same EGFP-actin as a probe have suggested, by contrast, that polymerization occurs exclusively at the leading edge. We performed FRAP experiments on XTC cells to compare SiMS to FRAP on the same cell type. We used speckle statistics obtained by SiMS to model the steady-state distribution and kinetics of actin in the lamellipodium. We demonstrate that a model with a single diffuse actin species is in good agreement with FRAP experiments. A model including two species of diffuse actin provides an even better agreement. The second species consists of slowly diffusing oligomers that associate to the F-actin network throughout the lamellipodium or break up into monomers after a characteristic time. Our work motivates studies to test the presence and composition of slowly diffusing actin species that may contribute to local remodeling of the actin network and increase the amount of soluble actin.
authors: Department of Physics, Lehigh University, Bethlehem, Pennsylvania, USA.
authors: Matthew B
authors: MB
authors: Smith
authors: Tai
authors: T
authors: Kiuchi
authors: Naoki
authors: N
authors: Watanabe
authors: Dimitrios
authors: D
authors: Vavylonis
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D003198:Computer Simulation; D004058:Diffusion; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D036681:Fluorescence Recovery After Photobleaching; D049452:Green Fluorescent Proteins / Q000378:metabolism; D007700:Kinetics; D008853:Microscopy; D008954:Models, Biological; D011554:Pseudopodia / Q000378:metabolism*
chemical_list: D000199:Actins; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins