Cytoskeleton 2 Flashcards
Cell locomotion involves changes in what?
Cytoskeletal organisation
What are the three major steps for the changes in cytoskeletal organsation for cell locomotion
1) Protrusion of filopodia, by actin polymerisation
2) Attachment, actin filaments connected by transmembrane proteins to substratum
3) Traction, contraction by myosin-actin interactions move the rear of the cell forward
What are the 4 parts of the cytoskeletal organisation
Actin cortex
Lamellpodium
Substratum
Myosin 2 surrounding the actin cortex
Actin myosin interactions do what for the cell body?
Pull the cell body forward, rearranges actin cortex, facilitates formation of stress fibres and contraction
External molecules guide cells and axons by binding what?
By binding to cell surface receptors
Bacteria produce what which binds to cell surface receptors?
Chemoattractants
The cell surface receptors bound to chemoattractants activate what 2 pathways?
Rac and Rho
What do the Rac and Rho pathways do
Rac regulates actin polymerisation which means lamellipodial extension
Rho regulates myosin activity which means actin filament bundling, stress fibers,
Microtubules are made of what dimers and assemble how?
Tubulin heterodimers which assemble head to tail to create a polar filament
Microtubules can be organised into what?
Regularly spaced bundles in cells
Microtubules function in regulating what?
cell shape and vesicle transport
What proteins are required for the axon and for the dendrites?
Tau for Axon
MAP2 for dendrites
Cilia and flagella are comoposed of what?
Bundles of microtubules
Cilia functions in what?
Motility and signaling
Microtubules self assemble from what?
Tubulin subunits
Microtubules grow faster at what end?
Plus end than minus end
Microtubules alternate between what phases?
Phases of rapid assembly and disassembly, dynamic instability
What is the GTP cap made from?
T form of filament
In term of microtubules descrive what happens in random alterations of GTP cap
There is rapid growth of microtubule when there is a cap at the end.
The loss of the GTP (the GTP in B suubits is hydrolysed to GDP) cap causes shrinkage. The regain of the cap then causes growth of the MT.
If depolymerisation catches up with polymerisation then filament collapses - catastrophe
Microtubules rate limiting step is what like what else?
Nucleation like actin
Microtubules are nucleated by what complex?
Via what ends
Allows for rapid polymerisation at what ends?
Y tubulin ring complex
Via minus ends, alpha ends
Rapid polymerisation at Plus ends, beta
The centrosome is the major what?
Microtubule organising centre in animal cells
Describe the centrosome and explain how it works to form MT
The centrosome contains a pair of centrioles
The centrosomealso has nucleating sties, made of y tubulin ring complexes in the centrosome matrix.
The mictrotubules frow from the matrix of centrosome
What are the 2 proteins that can bind to microtubule ends and what do they do to the MT
MAP and Catastrophe factor (kinesin 13) are the proteins that can bind
MAP causes stabilisation of the MT, so the frequency of catastrophe is supressed and/or growth rate is enhanced resulting in longer, less dynamic MTs
Catastrophe factor (kinesin 13) causes destabilisation which means frequency of catastrophe increases resulting in shorter, more dynamic microtubules
stablised microtubules provide tracks for what around the cell?
Tracks for movement of materials around the cell
How are microtubules and the secretory biosynthetic pathway connected?
Vesicles move along MT tracks in the secretory biosynthetic pathway
motor proteins move organelles around what
Around the cell along MTs
What are the microtubule motor proteins?
Kinesins and Dyneins
Kinesins and dynein generate force by doing what?
Coupling ATP hydrolysis to conformational changes
Kinesins drive what end directed movement? What does dynein do?
Kinesisn drive + end directed
Dyneins drive negative end directed movement
