Axonal Transport Flashcards
What are the two main functions of the axon?
- AP conduction
2. Physical conduit for materials transport
Which end of the axon is the one that grows? What is the growing tip called? What tells the axon where to grow towards?
Plus end has a growth cone that is guided by transmembrane axon guidance receptors that respond to growth signals in the environment.
What are the basic steps involved in cargo vesicle formation and transport?
- Cargo synthesized in ER.
- Cargo is loaded into a vesicle and buds off from ER.
- ER bud goes to cis-Golgi for processing.
- Cargo buds off from trans-Golgi and goes to the mt for transport.
What is required for clathrin to associate with cargo as the vesicle forms around the cargo?
Adapter proteins confer specificity and help clathrin associate with the cargo in the formation of the vesicle.
What protein forms a three-pronged triskelia structure?
Clathrin
In which two locations is clathrin involved?
- Trans golgi
2. Plasma membrane for endocytosis
Which GTPase is responsible for pinching off the clathrin-coated vesicle?
dynamin
Coat proteins COPI helps traffic cargo from the _____ to the _____ while COPII helps traffic cargo from the _____ to the _____.
COPI: from golgi to the ER (retrograde)
COPII: from ER to the golgi (anterograde)
SNARE proteins help with vesicle ______ and ______.
docking and fusion
What is a t-SNARE? Name two t-SNAREs.
Target membrae SNAREs. SNAP-25 and syntaxin
What is a v-SNARE? Name one.
Vesicle SNARE. Synaptobrevin.
Describe the SNARE cycle.
- Syntaptobrevin binds to the t-SNAREs, forming the trans-SNARE complex.
- Action potential triggers fusion, cis-SNARE complex forms.
- NSP and alpha-SNAP bind to SNARE complex to help disassemble.
- Clathrin pit endocytoses the SNARE leftovers for re-use.
What do Rab proteins do?
Regulate vesicle trafficking and fusion by hydrolyzing GTP.
In the neuronal axon, on which end are mt “+” ends found?
Distal from the cell body.
In neuronal dendrites, on which end are mt “+” ends found?
Polarity is mixed in dendrites.
What are the two speeds of axonal transport?
Fast and slow!
How is specificity enhanced by kinesin molecules?
Many kinesin tail domains exist. The tail domains interact with adapter proteins on cargo to confer specificity.
Kinesin motor proteins move toward the _____ end of microtubules.
Trick question!
Most move towards the “+” end, but the KIFC family moves towards the “-“ end.
Which direction does dynein move?
Towards the “-“ end.
What is dynactin?
A large protein that interacts with dynein for activation. It includes p150 glued, Arp1 and dynamitin.
Describe the movement mechanism of kinesin.
- The kinesin globular head heavy chain binds to the mt and after binding releases ADP.
- ATP fills the nucleotide-binding domain on the head, causing the linker protein to throw itself forward.
- The other globular head is thrown forward due to the linker protein’s movement and attaches to the mt, releasing ADP, and starting the cycle over.
Describe the movement mechanism of dynein.
- ATP binding frees the dynein head from the microtubule.
- ATP hydrolysis causes the head to re-attach to the mt 8nm further up.
- The other head does the same and somehow this makes it walk.
Synaptic vesicles are moved via ________. Most cytoskeletal elements are moved via _________.
fast anterograde transport
slow anterograde transport
Name four diseases in which axonal transport may play a role.
- ALS
- Hereditary Spastic Paraplegia
- Huntington’s
- Charcot-Marie-Tooth Disease
