title: Actin cytoskeleton of chemotactic amoebae operates close to the onset of oscillations.
abstract: The rapid reorganization of the actin cytoskeleton in response to external stimuli is an essential property of many motile eukaryotic cells. Here, we report evidence that the actin machinery of chemotactic Dictyostelium cells operates close to an oscillatory instability. When averaging the actin response of many cells to a short pulse of the chemoattractant cAMP, we observed a transient accumulation of cortical actin reminiscent of a damped oscillation. At the single-cell level, however, the response dynamics ranged from short, strongly damped responses to slowly decaying, weakly damped oscillations. Furthermore, in a small subpopulation, we observed self-sustained oscillations in the cortical F-actin concentration. To substantiate that an oscillatory mechanism governs the actin dynamics in these cells, we systematically exposed a large number of cells to periodic pulse trains of different frequencies. Our results indicate a resonance peak at a stimulation period of around 20 s. We propose a delayed feedback model that explains our experimental findings based on a time-delay in the regulatory network of the actin system. To test the model, we performed stimulation experiments with cells that express GFP-tagged fusion proteins of Coronin and actin-interacting protein 1, as well as knockout mutants that lack Coronin and actin-interacting protein 1. These actin-binding proteins enhance the disassembly of actin filaments and thus allow us to estimate the delay time in the regulatory feedback loop. Based on this independent estimate, our model predicts an intrinsic period of 20 s, which agrees with the resonance observed in our periodic stimulation experiments.
authors: Max Planck Institute for Dynamics and Self-Organization, 37077 Göttingen, Germany.
authors: Christian
authors: C
authors: Westendorf
authors: Jose
authors: J
authors: Negrete
authors: Albert J
authors: AJ
authors: Bae
authors: Rabea
authors: R
authors: Sandmann
authors: Eberhard
authors: E
authors: Bodenschatz
authors: Carsten
authors: C
authors: Beta
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives / Q000235:genetics / Q000378:metabolism; D008841:Actin Cytoskeleton / Q000737:chemistry / Q000187:drug effects / Q000502:physiology*; D055592:Biophysical Phenomena; D002633:Chemotaxis / Q000187:drug effects / Q000502:physiology; D000242:Cyclic AMP / Q000494:pharmacology; D004023:Dictyostelium / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D005453:Fluorescence; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism; D044085:Microfluidics; D008954:Models, Biological; D010507:Periodicity; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D054378:Acetogenins
chemical_list: D015107:4-Butyrolactone; D000242:Cyclic AMP; D008840:Microfilament Proteins; D015800:Protozoan Proteins; D011993:Recombinant Fusion Proteins; C115237:actin interacting protein 1; C438920:coronin acetogenin; D054378:Acetogenins