BMS02-1004 Cytoskeleton Flashcards
What is cell polarity?
Movement of the cell and inside the cell
What shape protein is actin?
Globular
What forms actin filaments?
G-actin
Why is it important that actin filaments are polar?
To give it a + and - end
How are monomers added to the actin filament?
ATP has to be hydrolysed to the ADP
Give 3 functions of actin
Mechanical support
Cell motility
Cell shape changes and maintenance
How can we stop G actin polymerising?
Actin-sequestering proteins such as profiling and thymosin
Give some examples of intermediate filaments?
Keratin in epithelia
Neurofilamin
What’s the function of intermediate filaments?
Forms lamins which give structure and transcriptional regulation
Anchors cells at junctions
How are intermediate filament polymers formed?
Monomer forms a helical dimer, 2 of these join to form a tetramer, tatramers link up in a staggered formation to form the filament
Which features of the cytoskeleton can assemble quickly?
Microtubules and actin
What makes up a microtubule?
Alpha and beta tubulin
What gives microtubules polarity?
One end is alpha and the other is beta
How does actin cause movement? (3)
Push out protrusions at the front of the cell as actin polymerise
These adhere to focal adhesions (macromolecules) giving contractile force
The cell pulls against the anchorage point to move the cell forwards
What holds vesicles near the membrane?
Actin
Describe the movement of myosin and actin in muscles
Calcium binds to tropomyosin moving it away to reveal the myosin binding site on actin
Myosin binds and ATP is converted to ADP so the myosin tails moves
ADP is released so the myosin head relaxes and detaches
How does chemo affect the cytoskeleton?
Destabalise microtubules so cells can’t divide
What can diseases involving actin cause?
Deaf and blindness
What is epidermolysis bullosa simplex?
Mutations in keratin impacting the epidermis making the skin very sensistive
Plectin mutations can also cause this (giant protein with links to filaments, actin and tubules)
What is amyotrophic lateral sclerosis
Mutations in neurofilaments causing motor neuron degredation
What causes alzhiemers?
Tangled neurofilaments so microtubules can’t bind
What causes hereditary spastic paraplegia?
A mutations which causes an enzyme to sever microtubules
What does listeria bacteria do?
The cell engulfs it but the bacteria escapes from the vesicle, actin then polymerises on the bacteria so it’s active and can go into other cells
What does the vaccinia virus do?
The virus is engulfed but escapes from the vesicle, it replicates and microtubules carry it to the edge, actin then polymerises so it can escape from the cell
