Universiteit Leiden

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Doris Heinrich Lab (Biophysics of Cellular Dynamics)

Cellular Actin Dynamics

Actin Polymerization and Membrane Physics in Living Cells: Analysis of cell spreading mechanisms

Project description

The spreading of motile cells on a substrate surface is accompanied by reorganization of their actin network. We investigate spreading in the highly motile cells of Dictyostelium, identifying it as non-monotonic, and thus differing from the passage of spreading cells through a regular series of stages.
 
Quantification of the gain and loss of contact area revealed fluctuating forces of protrusion and retraction that dominate the interaction of Dictyostelium cells with a substrate. The molecular basis of these fluctuations is elucidated by dual-fluorescence labeling of filamentous actin together with proteins that highlight specific activities in the actin system.
 
Front-to-tail polarity is established by the sorting out of myosin-II from regions where dense actin assemblies are accumulating. Myosin-IB identifies protruding front regions, and the Arp2/3 complex localizes to lamellipodia protruded from these regions. Coronin is used as a sensitive indicator of actin disassembly to visualize the delicate balance of polymerization and depolymerization in spreading cells. Short-lived actin patches that co-localize with clathrin suggest that membrane internalization occurs even when the substrate-attached cell surface expands. We conclude that non-monotonic cell spreading is characterized by spatiotemporal patterns formed by motor proteins together with regulatory proteins that either promote or terminate actin polymerization on the scale of seconds.

Publications from our workgroup in the field of actin dynamics

  • S. Sackmann, F. Keber, and D. Heinrich, Physics of Cellular Movements, Annu. Rev. Condens. Matter Phys. 1:257-276 (2010)
  • Doris Heinrich, Simon Youssef, Britta Schroth-Diez, Ulrike Engel, Daniel Aydin, Jacques Blümmel, Joachim Spatz and Günther Gerisch,
  • Actin-cytoskeleton dynamics in non-monotonic cell spreading 
  • Cell Adhesion & Migration 2:2, 58-68; April/May/June 2008
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