THE CYTOSKELETAL SYSTEM 2011. 05. 03. Beáta...
Transcript of THE CYTOSKELETAL SYSTEM 2011. 05. 03. Beáta...
9. Mechanisms of cell migration
THE CYTOSKELETAL SYSTEM
2011. 05. 03.
Beáta Bugyi
University of Pécs, Medical School
Department of Biophysics
Cell migration, motility
1. Intracellular - inside the cell muscle contraction
movement of organelles
movement of intracellular pathogens Listeria monocytogenes
Eschericia coli
Rickettsia rickettsii
Shigella
Salmonella
movement of chromosomes
2. Locomotion - displacement of the cell ciliar / flagellar movement
based on a special organelle: cilium, flagellum
pseudopod formation
based on the cytoskeletal filaments
3. Cell shape chages CYTOSKELETON
Listeria monocytogenes Chromosome congression in starfish oocyte
Source: Lénárt Péter és mtsai Nature 436 2005
1. Intracellular movement
move cells through liquid media / move liquid around the cells
fiber-like, flexible, elongated membrane projections of eukaryotic cells (mm - mm)
axonemal structure (0.25 mm): 9+2 microtubules
proteins: microtubules, nexin, dynein, tektin
2. Locomotion - ciliar/flagellar
Cilium
respiratory system (lung epithelium)
Flagellum
spermatozoon
Cilium Flagellum
AXONEME
Tektin
(13)
(9)
2. Locomotion - ciliar/flagellar
flagellum cilium
structure axoneme axoneme
number / cell 1-2 >1000
function propeller-like motion
„waves”
back and forth beating
power stroke – recovery stroke
energy
source ATP ATP
2. Locomotion - ciliar/flagellar
Fibroblast v = 0.5 mm / min
Source: Klemens Rottner Institut für Genetik Universität Bonn
Keratocyte v = 10 mm / min
2. Locomotion – pseudopod formation
0. Stimulus - polarisation chemoatractant, substrate, neighbouring cells
1. Protrusion lamellipodium formation
2. Adhesion formation of new cell-substrate connections
3. Contraction formation of contractile acto-myosin bundles
retratction of the rear of the cell
translocation of the cell body
4. Disassembly of old adhesions
Phases of cell migration
HEP2G adenocarcinoma cells, stimulus: insulin gradient
Cytoskeletal components of cell migration
Lamella
Filopodium
Focal contacts
Lamellipodium
Source: LeClainche és mtsai Physiological Reviews 88 2008.
direction of movement
A simpified scheme of cell migration
PROTRUSION (front) polarised growth of branched actin
filaments (polymerisation)
force generation: actin polymerisation
treadmilling
RETRACTION (rear) antiparallel, linear actin filaments
force generation: acto-myosin
ADHESION support protrusive and contractile forces
mechanical coupling between the
cytoskeleton and the substrate
coupling
↓
efficiency of
cell migration
Lamellipodium (Lp) Lamella (Lm)
actin networks with different structural and dynamic properties at/close to the leading
edge
width / length: 0 – 0.5 mm / 100 – 200 nm
thin, narrow membrane projection width / length: 1 mm/10-20 mm
mechanism WAVE - Arp2/3 komplex
„branching” ?
distance from the
membrace 0 – 0.5 mm > 0.5 mm
dynamics fast turnover
taposómalom egyensúly, treadmilling slow turnover
structutre branched - „dendritic” – filaments linear, non-branched filaments
molecular components capping protein, ADF/cofilin, cortactin, ... tropomyosin, myosin, …
Protrusive actin structures lamellipodium and lamella
Lamellipodium and lamella a possible mechanism
Source: Bugyi Beáta és Marie-France Carlier Annual Reviews in Biophysics 39 2010.
goldfish fibroblast
GFP-actin, vinculin
Focal contacts
classification: size, shape, intracellular localistaion and molecular composition
FOCAL COMPLEXES small, dot-like structure (1 mm2)
near the plasma membrane
dynamic
integrin, talin, paxillin
FOCAL ADHESIONS 2 – 5 mm long strucutre
farther from the plasma membrane
more stable, less dynamic
associated to stress fibers
integrin, talin, paxillin, vinculin, a-aktinin, zyxin, aktopaxin
FIBRILLAR ADHESIONS elongated structure
farthest from the plasma membrane
associated to fibronection fibers
integrin, tenzin
Focal contacts - types, components
Source: LeClainche és mtsai Physiological Reviews 88 2008.
Focal contacts – as molecular clutches
mechanical coupling between the substrate and the cytoskeleton
„disengaged” OFF „engaged” ON
molecular connection between the cytoskeleton and the
substrate
the force generated by actin polymerisation results in
membrance projections at the front of the cell
PROTRUSION the force generated by acto-myosin complexes results in
retraction at the rear of the cell
TRANSLOCATION
no connection between the cytoskeleton and the
substrate
the force generated by actin polymerisation results in
retrograde flow of actin filaments
NO MOVEMENT
Study of actin-based movements in vitro Biomimetic model systems (next…)
N-WASP – Arp2/3 complex formin
mouse fibroblast
t = 3 h
chicken fibroblast
t = 2 h
mouse melanoma cell
t = 20 min
fish epidermal keratocyte
t = 4 min