title: Actin and PIP3 waves in giant cells reveal the inherent length scale of an excited state.
abstract: The membrane and actin cortex of a motile cell can autonomously differentiate into two states, one typical of the front, the other of the tail. On the substrate-attached surface of Dictyostelium discoideum cells, dynamic patterns of front-like and tail-like states are generated that are well suited to monitor transitions between these states. To image large-scale pattern dynamics independently of boundary effects, we produced giant cells by electric-pulse-induced cell fusion. In these cells, actin waves are coupled to the front and back of phosphatidylinositol (3,4,5)-trisphosphate (PIP3)-rich bands that have a finite width. These composite waves propagate across the plasma membrane of the giant cells with undiminished velocity. After any disturbance, the bands of PIP3 return to their intrinsic width. Upon collision, the waves locally annihilate each other and change direction; at the cell border they are either extinguished or reflected. Accordingly, expanding areas of progressing PIP3 synthesis become unstable beyond a critical radius, their center switching from a front-like to a tail-like state. Our data suggest that PIP3 patterns in normal-sized cells are segments of the self-organizing patterns that evolve in giant cells.
authors.affiliation: University Potsdam, Institute of Physics and Astronomy, 14476 Potsdam-Golm, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Gerhardt
authors.affiliation: Max Planck Institute of Biochemistry, 82152 Martinsried, Germany.
authors.forename: Mary
authors.initials: M
authors.lastname: Ecke
authors.affiliation: University Potsdam, Institute of Physics and Astronomy, 14476 Potsdam-Golm, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Walz
authors.affiliation: Max Planck Institute of Biochemistry, 82152 Martinsried, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Stengl
authors.affiliation: University Potsdam, Institute of Physics and Astronomy, 14476 Potsdam-Golm, Germany.
authors.forename: Carsten
authors.initials: C
authors.lastname: Beta
authors.affiliation: Max Planck Institute of Biochemistry, 82152 Martinsried, Germany gerisch@biochem.mpg.de.
authors.forename: Günther
authors.initials: G
authors.lastname: Gerisch
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism*; D000199:Actins / Q000378:metabolism*; D002459:Cell Fusion / Q000379:methods; D002462:Cell Membrane / Q000378:metabolism*; D002465:Cell Movement; D016764:Cell Polarity; D048429:Cell Size; D004023:Dictyostelium / Q000378:metabolism / Q000502:physiology*; D060733:Electromagnetic Radiation; D015726:Giant Cells / Q000502:physiology*; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism
chemical_list: D000199:Actins; D018129:Phosphatidylinositol Phosphates; C060974:phosphatidylinositol 3,4,5-triphosphate
keywords: Actin waves; Cell fusion; Cell polarity; Excitable systems; PIP3 signals