dictyNews
Electronic Edition
Volume 42, number 15
June 10, 2016

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Abstracts
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Actin organization in cells responding to a perforated surface, 
revealed by live-imaging and cryo-electron tomography

Marion Jasnin, Mary Ecke, Wolfgang Baumeister, Günther Gerisch


Structure-Cell, in press

In a three-dimensional environment, motile cells accommodate 
their protruding and retracting activities to geometrical cues. 
Dictyostelium cells migrating on a perforated film explored 
its holes by forming actin rings around their border and 
extending protrusions through the free space. The response 
was initiated when an actin wave passed a hole, and the rings 
persisted only in the PIP3-rich territories surrounded by a 
wave. To reconstruct actin structures from cryo-electron 
tomograms, actin rings were identified by cryo-correlative 
light and electron microscopy, and thin wedges of relevant 
regions were obtained by cryo-focused ion beam milling. 
Retracting stages were distinguished from protruding ones by 
the accumulation of myosin-II. Early actin rings consisted of 
filaments pointing upright from the membrane, entangled with 
a meshwork of filaments close to the membrane. Branches 
identified at later stages suggested that formin-based 
nucleation of filaments was followed by Arp2/3-mediated 
network stabilization, which prevented buckling of the 
force-generating filaments.


submitted by: Günther Gerisch [[log in to unmask]]
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[End dictyNews, volume 42, number 15]