Session 5: Cytomotility

Question 1

What triggers cytomotility?

Answer 1

signals from the environment initiate movement
- chemical signals can be received by cell surface receptors
- environmental signals can form chemical gradients

Question 2

What are the two different cytomotility types/migration responses?

Answer 2

chemotaxis - chemotactic cells move up gradient, toward higher concentration of attractive factor IN SOLUTION
- ex. wound fluid - WBC migrates toward the wound bc of gradient of bacterial debris solubilized into the wound fluid

haptotaxis - haptotactic cells move up gradient, toward higher amount of attractive factor BOUND TO SURFACE
- ex. epithelial cell migrating towards wound bed - cells are triggered to recover the wound bc of the gradients of depositing/attractive factors

Question 3

List the four roles of cytoskeleton

Answer 3

cellular level “amoeboid” motility
- cell movement in response to chemotactic or haptotactic stimulus
- metastasis
- infection clearing
- wound healing

Question 4

Describe cellular movement in response to chemotactic or haptotactic stimulus

Answer 4

• mostly ACTIN (MF) based mechanism
• some MTs are used to extend membrane

Question 5

Describe metastasis through cellular motility

Answer 5

malignant cells migrate beyond tumor (spreads cancer to other areas)

Question 6

Describe responsibility of cellular motility on infection clearing

Answer 6

WBC migration towards infection through cellular amoeboid movement to fight infection

Question 7

How does cellular motility lead to wound healing?

Answer 7

epithelial and fibroblast migration towards wound

Question 8

Explain treadmilling relative to movement of actin subunits

Answer 8

polymerization adds actin monomers to the + end
depolymerization removes actin monomers from the - end
result: there is net gain at the + end cell edge –> pushes membrane forward and extends stress fibers

Question 9

Explain the actual process of microfilaments moving through the cell (PAR) - STEP 1

Answer 9

Protrusion - extension of the + end
- actin is polymerized at the + end of the membrane
- narrow (filapodia)
- flat (lamellipodia)

Question 10

Explain the process of microfilaments moving through the cell (PAR) - STEP 2

Answer 10

Adhesion - connection to the cell
- adhesion plaque = focal contact
- stress fibers are made of MFs (connect to focal contacts)
- for the cell to properly migrate, it has to be connected to the cell to “ground it”

Question 11

Explain the process of microfilament migration through the cell (PAR) - STEP 3

Answer 11

Retraction - release of the - end
- adhesion plaque disassembly (depolymerization)
- detaches from the substrate
- the cell must detach from the tail end in order to move forward

Question 12

What type of structures do microfilaments have within the cell to cause intracellular movement?

Answer 12

• transient structures
• stable structures

Question 13

What are transient MF structures responsible for inside the cell?

Answer 13

contractile rings - responsible for the division of daughter cells
- in cell division

vesicle movement
- actin filament with myosin 1 motor protein
- myosin motor proteins are connecting/releasing the vesicle from the surface it’s attached to to get migration

filopodia for migration

extensions for phagocytosis

Question 14

Explain how stable microfilament structures are responsible for intracellular movement.

Answer 14

sacromeres for muscle contraction
- long term association of actin and myosin 2 motor proteins
- low phospho-titin (accessory protein) is compatible with stability of sarcomere

Question 15

Explain the ways tubulin-based movement impacts activity within the cell

Answer 15

membrane extension
- MT positive ends at the edge of the cell are minor but important component of amoeboid movement

chromosome seperation
- coordinated polymerization at midline
- depolymerization at pole

Question 16

What would the effect of taxol be on the mitotic spindle?

Answer 16

taxol stabilizes the polymer and prevents depolymerization –> the cell isn’t going to divide

Question 17

What type of cytoskeletal system is responsible for cilia and flagella?

Answer 17

microtubules

Question 18

What is the role of motor proteins?

Answer 18

form bridge between microtubule and organelle
- requires ATP for movement
- ONE WAY movement only
- a type of MAP (microtubule-associated protein)

Question 19

What are the two distinct types of motor proteins?

Answer 19

dyeneins - move towards cell interior (towards - end)
kinesins - move towards cell edge (towards + end)

Question 20

Explain how MTs are responsible for transport through neurons

Answer 20

• neuron protein synthesis
• transport thru axons and dendrites (dependent on intact microtubule: organelles or secretory vesicles)
• two way transport (bc of kinesins and dyneins)

Question 21

What is the role of cilia and flagella?

Answer 21

• has stable core of microtubules
• motor proteins carry cargo along MT core

Question 22

What conditions would cilia be a good drug target for? why?

Answer 22

congestion/cystic fibrosis
- researchers found taste receptors for bitter compounds on cilia membrane –> cells exposed to bitter compounds increased Ca2+ levels and increased ciliary beating
- targeting cilia will target the bitter compounds found on cilia