Session 5: Cytomotility Flashcards
What triggers cytomotility?
signals from the environment initiate movement
- chemical signals can be received by cell surface receptors
- environmental signals can form chemical gradients
What are the two different cytomotility types/migration responses?
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
List the four roles of cytoskeleton
cellular level “amoeboid” motility
- cell movement in response to chemotactic or haptotactic stimulus
- metastasis
- infection clearing
- wound healing
Describe cellular movement in response to chemotactic or haptotactic stimulus
- mostly ACTIN (MF) based mechanism
- some MTs are used to extend membrane
Describe metastasis through cellular motility
malignant cells migrate beyond tumor (spreads cancer to other areas)
Describe responsibility of cellular motility on infection clearing
WBC migration towards infection through cellular amoeboid movement to fight infection
How does cellular motility lead to wound healing?
epithelial and fibroblast migration towards wound
Explain treadmilling relative to movement of actin subunits
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
Explain the actual process of microfilaments moving through the cell (PAR) - STEP 1
Protrusion - extension of the + end
- actin is polymerized at the + end of the membrane
- narrow (filapodia)
- flat (lamellipodia)
Explain the process of microfilaments moving through the cell (PAR) - STEP 2
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”
Explain the process of microfilament migration through the cell (PAR) - STEP 3
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
What type of structures do microfilaments have within the cell to cause intracellular movement?
- transient structures
- stable structures
What are transient MF structures responsible for inside the cell?
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
Explain how stable microfilament structures are responsible for intracellular movement.
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
Explain the ways tubulin-based movement impacts activity within the cell
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
What would the effect of taxol be on the mitotic spindle?
taxol stabilizes the polymer and prevents depolymerization –> the cell isn’t going to divide
What type of cytoskeletal system is responsible for cilia and flagella?
microtubules
What is the role of motor proteins?
form bridge between microtubule and organelle
- requires ATP for movement
- ONE WAY movement only
- a type of MAP (microtubule-associated protein)
What are the two distinct types of motor proteins?
dyeneins - move towards cell interior (towards - end)
kinesins - move towards cell edge (towards + end)
Explain how MTs are responsible for transport through neurons
- neuron protein synthesis
- transport thru axons and dendrites (dependent on intact microtubule: organelles or secretory vesicles)
- two way transport (bc of kinesins and dyneins)
What is the role of cilia and flagella?
- has stable core of microtubules
- motor proteins carry cargo along MT core
What conditions would cilia be a good drug target for? why?
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
