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TZID:Europe/Paris
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BEGIN:VEVENT
UID:1-140@lptms.universite-paris-saclay.fr
DTSTART:20130614T140000Z
DTEND:20130614T140000Z
DTSTAMP:20130628T083047Z
URL:http://www.lptms.universite-paris-saclay.fr/seminars/physics-biology-i
 nterface-seminar-michael-murrell/
SUMMARY:Physics-Biology interface seminar : Michael Murrell - Amphi BLANDIN
  du LPS de la Faculté des Sciences d’Orsay (Bâtiment 510) - 14 Juin 13
  14:00
DESCRIPTION:Mechanical Force Generation and Turnover in the Cell Cytoskelet
 on\nMichael Murrell (University of Wisconsin\, Madison)\nMyosin II motors 
 drive contractility of the cortical actin network\, enabling shape change 
 and cytoplasmic flows underlying diverse physiological processes ranging f
 rom cell division and migration to tissue morphogenesis. Yet\, despite its
  importance\, the mechanisms that describe contractility and the generatio
 n of mechanical forces within the cortex are not well understood. We recap
 itulate contractility in vitro\, through the development of a minimal mode
 l of the cell actomyosin cortex by coupling a two-dimensional\, cross-link
 ed F-actin network decorated by myosin thick filaments to a model cell mem
 brane. Myosin motors generate both compressive and tensile stresses on F-a
 ctin and consequently\, induce large bending fluctuations. Over a large ra
 nge of crosslinking\, we show the extent of network contraction correspond
 s exactly to the extent of individual F-actin shortening via buckling. Thi
 s demonstrates an essential role of buckling in facilitating local compres
 sion to enable mesoscale network contraction of up to 80% strain. Buckled 
 F-actin at high curvatures are prone to severing and thus\, compressive st
 resses mechanically coordinate contractility with F-actin severing\, the i
 nitial step of F-actin turnover. Finally\, the F-actin curvature acquired 
 by myosin-induced stresses can be further constrained by adhesion of the n
 etwork to a membrane\, accelerating filament severing but inhibiting the l
 ong-range transmission of the stresses necessary for network contractility
 . Thus\, the extent of membrane adhesion can regulate the coupling between
  network contraction and F-actin severing. These data demonstrate the esse
 ntial role of the non-linear response of Factin to compressive stresses in
  potentiating both myosin-mediated contractility and filament dynamics.
LOCATION:Amphi BLANDIN du LPS de la Faculté des Sciences d’Orsay (Bâtim
 ent 510)\, 15 Rue Georges Clemenceau\, orsay\, France
GEO:48.698187;2.181768
X-APPLE-STRUCTURED-LOCATION;VALUE=URI;X-ADDRESS=15 Rue Georges Clemenceau\,
  orsay\, France;X-APPLE-RADIUS=100;X-TITLE=Amphi BLANDIN du LPS de la Facu
 lté des Sciences d’Orsay (Bâtiment 510):geo:48.698187,2.181768
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