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DTSTART:20200329T030000
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DTSTART:20191027T020000
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DTSTAMP:20260404T064849Z
UID:5e15dd30bde75907576106@ist.ac.at
DTSTART:20200124T140000
DTEND:20200124T153000
DESCRIPTION:Speaker: Jaakko Lehtimäki\nhosted by Carl-Philipp Heisenberg\n
 Abstract: Cell migration is governed by both protrusive and contractile ac
 tin filament arrays\, but the relative contributions of these structures d
 iffer\, depending on the cell-type and extracellular environment. Contract
 ile actomyosin bundles\, ventral stress fibers\, are the most prominent co
 ntractile actomyosin structures in animal non-muscle cells. They are impor
 tant for cell morphogenesis\, adhesion\, migration\, and mechanosensing. T
 he function of ventral stress fibers depends on periodic\, bipolar assembl
 ies of non-muscle myosin II (NMII) filaments along thick actin filament bu
 ndles\, which are connected to focal adhesions at their both ends. In migr
 ating cells\, ventral stress fibers are generated from the pre-existing ne
 twork of two other types of actin bundles: transverse arcs and dorsal (rad
 ial) stress fibers. In addition to thick ventral stress fibers that are ty
 pically enriched at the lamellum of motile cells\, many cell-types also ex
 hibit thinner stress fibers at their perinuclear region. Whether also thes
 e structures are generated from the pre-existing network of transverse arc
 s and dorsal stress fibers\, or through a novel mechanism\, was not known.
  Moreover\, the mechanisms underlying the assembly of functional NMII bund
 les for stress fibers has remained elusive.I will present data demonstrati
 ng that UNC-45a protein is critical for efficient folding of NMII molecule
 s\, as well as for their assembly into functional bipolar NMII filaments. 
 Hence\, the myosin chaperone UNC-45a is critical for the assembly of contr
 actile stress fibers in non-muscle cells (Lehtimki et al.\, J Cell Biol\, 
 2017). Moreover\, I will present new unpublished data demonstrating that t
 hin perinuclear stress fibers are generated through a novel mechanism. I r
 evealed that perinuclear stress fibers assemble de novo\, through a NMII p
 ulse-dependent reorganization of the cortical actin meshwork beneath the n
 ucleus. This leads to the formation of a contractile actomyosin bundle\, a
 nd subsequent enrichment of focal adhesion components at the ends of the b
 undle. Thus\, contractile stress fibers can be assembled by at least two d
 ifferent mechanisms\, which are both dependent on the NMII activity.
LOCATION:Meeting room 2nd floor / Bertalanffy Bldg. (I04.2OG - LAB)\, ISTA
ORGANIZER:lalesch@ist.ac.at
SUMMARY:Jaakko Lehtimäki: How to assemble contractile actomyosin bundles i
 n migrating cells?
URL:https://talks-calendar.ista.ac.at/events/2479
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