Cytoskeleton

Cytoskeleton

1. microtubules

   • characteristics
     • hollow
     • variable legnth
       • growth/shrink
   • cell shape
   • movement
   • cell division
   • target of anti-cancer drugs
   • structure
     • a and b tubulin
       • 13 heterodimers
         • protofilments
       • polarity
     • + end grows faster
   • types
     • cytoplasmic
       • mitotic spindle
         • interphase - long lasting
         • metaphase - short lasting
   • Formation
     • polymerisation then nucleoside hydrolysis
     • - addition slow
       • hydrolysis catches up
     • + addition fast
       • hydrolysis lags
     • treadmilling
       • different assembly rates
       • adding dimers T
       • added dimers D
         • GDP
     • loss of GTP cap - shrinkage
       • below - GDP dimers
         • less stable
   • chromosomes
     • kinetochore MT into paired chro
       • exert force to align chro on met plate
         • generated at kinetochores
     • Polar MT overlap
       • longer as poles move apart
         • sliding then pulling
     • astral MT from astras
     • spindle pole
       • organising centre in yeast
       • 2 x centrosome
   • organelle movement
     • saltatory movement
     • motor proteins
     • one at a time
     • retrograde/anterograde

2. organising centres

   • controsome
     • g tubulin
     • paired centrioles
   • Y-tubulin ring
     • nucleating sites
       • alpha end exposed
   • Basal bodies
     • cilia/flagella
       • 9 + 3 MT
   • spindle pores
     • MT in mitosis

3. MAPS

   • assembly promoting
   • MAP 2 dendrites
   • Tau2 axons
   • motor proteins
     • dynein
       • to -
       • indirect bind
     • kinesin
       • to +
       • directly bound to organelle
     • ATP

4. microfilaments

   • fibres
     • homomeric actin
       • Globular
       • filamentous
   • striated muscle
     • Ask Ac
   • Smooth muscle
     • Asm Ysm
   • non muscle
     • B Y
   • assembly
     • nucleation lag phase
       • trimer nucleation
         • oligomers
     • elongation growth phase
     • steady state equilibrium
     • treadmiling
     • ARP complex in viv
       • MF grow from
   • dynamics
     • more stable
     • remodelling changes cell shape
       • acrosome - MF extend rapidly
   • actin binding proteins
     • Gelsolin
       • caps/severs/nucleates
     • profilin
       • inhibit monomer binding
     • fimbrin
       • bundling fibres
   • cytokinesis
     • form contractile ring
       • actin myosin filaments
     • mid body
       • cleaves and MT disassembly
         • patches 90degrees to surface

5. intermediate filaments

   • ropes
     • coiled coil
       • cross linking
       • protofilament 8 tertrameres
   • homo/heteropolymeric
   • different composition for each cell
   • structural support
     • nuclear lamina
       • dissasembly at prometaphase
         • breakdown
           • cage
             • organisation of nuclear membrane by lamins
     • hair, muscle, fingernails
     • most cytoplasmic
   • composition
     • 1+2 epithelial keratins
     • 3 muscle desmins
     • 4 neurofilaments
     • 5 nuclear lamins

6. cilia and flagella

   • MT motility/appendages
   • axoneme
     • 9 + 2 MT doublets
       • outerdoublets
         • incomplete B
         • complete A
     • axosome central pair loss
     • striated rootlets anchors into cell
     • dynein arms
       • MT activated with contact of dynein arms to another
         • sliding in isolated
         • bending in flagelle/cilia
       • inner -movement shape
         • cilia - whip
         • flagella - stroke
       • outer - power

7. Myosin

   • 2 heads, dimer, bound ATP
   • coiled coil
     • 2 alpha helixes

8. Amoeboid movement

   • actin/myosin filament turnover
   • gel-sol transition
   • actin polymerisatoin
     • pseudopods
       • organelle free zone
       • grip to ECM
     • actin cortex
       • underlying plasma membrane
     • filopodia in non muscle cells
       • lamellipodia
   • Bug chase
     • neutrophils
       • kill bacteria in RBC
         • chemo bacteria sensing
     • polarised
     • Myosin 2 contraction at back
       • motor proteins
     • focal contacts
       • integrins
     • actin filaments detached at back