B3.060 Prework 1 Cytoskeleton

Question 1

what are the 3 main types of filaments in the cytoskeleton

Answer 1

actin
microtubules
intermediate

Question 2

actin characteristics

Answer 2

shape of the cell surface and cell migration

5-9 nm diameter

Question 3

microtubules characteristics

Answer 3

positions of membrane enclosed organelles, intracellular transport and cell division
25 nm diameter
hollow cylinder of 13 protofilaments

Question 4

intermediate filaments characteristics

Answer 4

mechanical strength

9-11 nm diameter

Question 5

how is actin formed?

Answer 5

forms from globular actin (G-actin) monomers + ATP
added preferentially to + end of growing filament
2 stranded, helical structure forms and concentrated in cortex of the cell, below the membrane

Question 6

what is the function of the Arp2/3 complex

Answer 6

nucleates assembly to form a web and remains associated with the - end
enhances filament polymerization

Question 7

what are Arps?

Answer 7

actin related proteins
closely resemble actin
form a complex that resides on the minus end of a nucleated actin filament
can be used to form an actin web

Question 8

activation of which protein by which protein leads to actin polymerization and cytoskeletal reorganization?

Answer 8

ZAP-70 > LAT & SLP-76 > Vav > actin poly and cyt reorg

Question 9

list the steps of WASp mediated actin filament nucleation

Answer 9

1. TCR binding
2. leads to activation of Vav-1
3. activates cdc42
4. cdc42 binds to WASp
5. WASp assumes open configuration
6. Fyn-mediated phosphorylation stabilizes the open conformation
7. Arp 2/3 binds
8. actin filament polymerization ensues
9. development of immune synapse is established

Question 10

what immune cell functions are facilitated by actin based changes

Answer 10

chemokine mediated cell migration
immune synapse
-T cell activation
-cytotoxic T cell mediated target killing