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Research Paper
Actin-cytoskeleton dynamics in non-monotonic cell spreading
Doris Heinrich, Simon Youssef , Britta Schroth-Diez, Ulrike Engel, Daniel Aydin, Jacques Blümmel, Joachim Spatz and Günther Gerisch
volume 2 | issue 2
april/may/june 2008Pages: 58 - 68
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The spreading of motile cells on a substrate surface is accompanied by reorganization of their actin network. We show that spreading in the highly motile cells of Dictyostelium is non-monotonic, and thus differs 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.
Authors
Doris Heinrich
Ludwig-Maximilians-Universität
Simon Youssef
Ludwig-Maximilians-Universität
Britta Schroth-Diez
Max Planck Institute of Molecular Cell Biology and Genetics
Ulrike Engel
Nikon Imaging Center at the University of Heidelberg
Daniel Aydin
Max Planck Institute for Metals Research
Jacques Blümmel
Max Planck Institute for Metals Research
Joachim Spatz
Max Planck Institute for Metals Research
Günther Gerisch
Max-Planck-Institut für Biochemie