title: Different modes of state transitions determine pattern in the Phosphatidylinositide-Actin system.
abstract: BACKGROUND
  In a motile polarized cell the actin system is differentiated to allow protrusion at the front and retraction at the tail. This differentiation is linked to the phosphoinositide pattern in the plasma membrane. In the highly motile Dictyostelium cells studied here, the front is dominated by PI3-kinases producing PI(3,4,5)tris-phosphate (PIP3), the tail by the PI3-phosphatase PTEN that hydrolyses PIP3 to PI(4,5)bis-phosphate. To study de-novo cell polarization, we first depolymerized actin and subsequently recorded the spontaneous reorganization of actin patterns in relation to PTEN.
  
  
  RESULTS
  In a transient stage of recovery from depolymerization, symmetric actin patterns alternate periodically with asymmetric ones. The switches to asymmetry coincide with the unilateral membrane-binding of PTEN. The modes of state transitions in the actin and PTEN systems differ. Transitions in the actin system propagate as waves that are initiated at single sites by the amplification of spontaneous fluctuations. In PTEN-null cells, these waves still propagate with normal speed but loose their regular periodicity. Membrane-binding of PTEN is induced at the border of a coherent PTEN-rich area in the form of expanding and regressing gradients.
  
  
  CONCLUSIONS
  The state transitions in actin organization and the reversible transition from cytoplasmic to membrane-bound PTEN are synchronized but their patterns differ. The transitions in actin organization are independent of PTEN, but when PTEN is present, they are coupled to periodic changes in the membrane-binding of this PIP3-degrading phosphatase. The PTEN oscillations are related to motility patterns of chemotaxing cells.
authors: Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany. gerisch@biochem.mpg.de
authors: Günther
authors: G
authors: Gerisch
authors: Mary
authors: M
authors: Ecke
authors: Dirk
authors: D
authors: Wischnewski
authors: Britta
authors: B
authors: Schroth-Diez
mesh_terms: D008841:Actin Cytoskeleton / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure*; D001683:Biological Clocks / Q000187:drug effects / Q000502:physiology; D002465:Cell Movement / Q000502:physiology; D016764:Cell Polarity; D022081:Cell Surface Extensions / Q000378:metabolism*; D002478:Cells, Cultured; D004023:Dictyostelium / Q000502:physiology*; D055786:Gene Knockout Techniques; D051059:PTEN Phosphohydrolase / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D021381:Protein Transport
chemical_list: D019869:Phosphatidylinositol 3-Kinases; D051059:PTEN Phosphohydrolase