Lecture 6.2 C. elegans Flashcards
How is the chemosensory cilia in contact with the outside world? What can it do?
Chemosensory cilia: in contact with the outside world at the ends of dendrites of axons.
-> Can detect chemicals, pheromones, etc.
How long is it? What does it exist of?
Cilium =hair-like structure with a membrane. Core = microtubule structure that forms a pipe from the base to the tip. 7-8 microm long. Different parts:
1) Dendrite & PCMC
2) transition zone (diffusion barrier keeping certains proteins inside the cilium different from the rest)
3) Proximal segment: microtubules are doublets, specific for C. elegans
4) distal segment where microtubules are singlets, tip is on contact with outside world.
3 motor proteins that make up the transport mechanism, essential for building the cilia structure/function. What are they called? In what direction do they transport?
OSM3 and kinesin: transport base to tip
Dynein = takes care of transport tip to base
What are IFT-A and -B used for?
required for building maintenance & functioning of cilia
What was done to visualize single-motor tracking & cargo handover?
Modified worms were made that fluoresce. Single-motor tracking: color imaging. Cargo handover from kinesin-2 to OSM-3: change in fluorescence colour.
What does the IFT-train velocity (=snelheid) vary with? How does it vary?
Varies with location.
>IFT-trains accelerate gradually
>IFT-train intensity stays constant
How does Kinesin-2 (slow motor) hand over cargo and to who?
> Kinesin-II(slow motor) graduallyhands overIFT-cargo toOSM-3(fastmotor)
Visualization & tracking of individual kinesins: what was discovered about the motors?
They switch directions: turn from drivers into passengers and vice versa
Where does kinesin-2 cycle and where does OSM-3 cycle?
Kinesin-2: between base and start proximal segment
OSM3: between transition zone & tip
Driver-to passenger switch almost instantaneous: hardly free motors (except for base)
Current view on IFT in c. Elegans?
- Train backbone moves in one go
- Motors dock on and off trains
What is OCR-2?
- OCR-2 is a TRPV cation channel involved in signaling
How is IFT trans-membrane cargo, OCR-2, transported?
In dendrite: active transport driven by dynein. It is embedded in RAB-8 vesicles.
What kind of transport takes place across the transition zone?
Active
what kind of movement takes place in the proximal & distal segment?
Saltatory movement (=Saltatory conduction (from the Latin saltare, to hop or leap) is the propagation of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of action potentials.)
Choosing between mostly IFT, normal diffusion, subdiffusion and little IFT, what kind of transport takes place in the TZ (transition zone), PS (proximal segment), DS (distal segment) and the Tip?
> TZ: mostly IFT
PS: normal diffusion + a bit of IFT
DS: subdiffusion + IFT
Tip: subdiffusion