Lecture 4 - Cytoskeletal Interactors

Question 1

(i) What are MT +end tracking proteins (+TIPs)?

(ii) What is the most well known Family?

Answer 1

(i) Proteins that accumulate at growing microtubule + ends
(ii) End-binding (EB Proteins) e.g., EB1, EB2, EB3

Question 2

What is the General Structure of EB Proteins?

(4 Points)

Answer 2

• N-terminal domain - highly conserved, adopts CH fold
• Coiled-coiled domain - a-helical, mediates dimerisation of monomers
• EB Homology (EBH) domain
• Acidic tail

Question 3

What is the Function of EB Proteins?

Answer 3

Core components of +TIP networks, which recruit other proteins to growing +ends by recognising GTP-cap

Question 4

How does High concentration of EB proteins influence MT dynamics?

Answer 4

Increased Catastrophe, but more rapid Recovery

Question 5

(i) What is STIM1 (Stromal Interacting Molecule 1)?

(ii) What is its Function?

Answer 5

(i) ER Calcium Sensor, which is recruited to MTs by EB1 and EB3

(ii) STIM1-EB Interactions link growing microtubules to the ER and is involved in coordinating the navigation of neural growth cones
* Also required for ER remodelling, Ca2+ signalling and Axon navigation

Question 6

How does STIM1-KD influence neurons?

(2 Points)

Answer 6

• Impaired Axon Navigation and decreased growth cone production
• Impaired ER remodelling and Calcium Storage

Question 7

How was regulation of IF distribution by Actin/MT networks visualised?

(3 Points)

Answer 7

Photobleaching of GFP-labelled Vimentin with:
* Actin Depolymerisation/Myosin II Inhibition - blocked IF retrograde flow
* Kinesin/Dynein-KD - influenced IF distribution depending on direction of motor travel

Question 8

(i) What is MT Buckling?

(ii) When does it occur?

(3 Points)

Answer 8

(i) Bending of MT after compression (typically short wavelength)
(ii) Occurs:
* On Interaction of MT with membrane
* Periodically in beating heart cells