Flashcards in Cytoskeleton & Response to Mechanical Stress Deck (57):
Inside of cell → surrounds organelles
Cytoskeleton is a complex network of?
It extends through ____ and attaches to?
Complex network of interconnected filaments and tubules → extends throughout cytosol, attaches to inner surface of plasma membrane
Cytoskeleton plays a role in:
1. Cell movement
2. Cell division
3. Internal organization (allows cell to assume shapes)
4. Cell signaling
5. Cell adhesion
Major structural elements of cytoskeleton
3. Intermediate fibers
25 nm (largest)
7 nm (smallest)
Intermediate filament diameter
Ways that microtubules, microfilaments and intermediate filaments/fibers are unique to each other
3. Intracellular distribution
4. Formed by polymerization of different proteins
5. Accessory proteins
1. Cellular movement (cilia, flagella)
2. Maintenance of nerves and axons
3. Spatial orientation in cytosol → govern location of organelles
Microtubules are cylinders. Tell me about their characteristics.
3. Outer diameter = 25 nm, inner diameter = 15 nm
4. Length varies
Wall of microtubule cylinders consists of:
13 protofilaments arranged side-by-side, forming a hollow center
Forms microtubule cylinder
Heterodimer of tubulin
2 types of tubulin
1. Tubulin synthesis
2. Non-covalent binding
Forms alpha-beta heterodimers
How many tubulin isoforms in brain?
5 alpha, 5 beta
Radiate toward periphery → forms centrosome
How are microtubules regulated?
Microtubule associated proteins (MAPs)
Where do MAPs bind?
What is their function?
Regular intervals along wall of microtuble:
1. Allows interaction with other filaments
2. Regulate growth of microtubule
2 types of MAPs in brain
1. Motor MAPs
2. Non-motor MAPs
Use ATP to drive transport of vesicles and organelles
Function of non-motor MAPs
1. Control microtubule organism in cytoplasm
2. Nervous system
Non-motor MAP in brain reinforced by microtubules
Neurites can differentiate into?
1. Contractile fibers of muscle cells (actin)
3. Cell cortex
Cell cortex function
Mechanical support of plasma membrane → responsible for cell-surface movement
Cell cortex is a dense network of microfilaments. Tell me about it.
Microfilaments are attached to the inner face of plasma membrane → causes cell surface to be structurally rigid (important in cell shape)
1. Extremely abundant → in virtually all cells
2. Building block of microfilaments
Polymerization of G-Actin
2 major groups of actin
beta-actin and gamma-actin
Cell surface extensions
Extend from edge of migrating cell → aids in movement of cell
Actin-binding protein functions
1. Stabilize filaments
2. Generate force (myosin)
Intermediate filament roles
Intermediate filament properties
1. Most stable
2. Least soluble
2. Scaffold (supports entire cytoskeleton)
Intermediate filament structure differs based on?
Amino acid composition between tissues
6 classes of intermediate filaments
I and II: epithelial cells
III: muscle, glial, CT
IV: nerve cels
V: all cells
VI: embryonic nervous system
How is mechanical stress important in normal physiological processes?
1. Cell growth
2 diseases in which mechanical stress is especially relevant
Heart and lung diseases
Adaptation from mechanical stress occurs via changes in:
3. Gene expression
Uses tension and compression to provide support
Tensegrity = tensional integrity
What generates tension?
What bears compression?
What provides elasticity?
How does cytoskeleton adapt to stress?
Transmits stress to rest of structure → aligns tension bearing forces with direction of stress
Signaling response to stress
ECM recognizes stress → transmits signal into cell so it can adapt as needed
3 responses to stress
1. Outside-in signaling
2. Regulation of nuclear access
3. Adaptation of cytoskeleton and ECM
How is nuclear access regulated as a response to stress?
Alters pore size leading to nucelus
How does membrane respond to stress?
Mechanically gated ion channels
Microtubule organizing center
Neurites → Axons regulated by?
Neurites → Dendrites regulated by?
Microfilaments found in what cells?
Almost all eukaryotic cells
Cell cortex is made of?
Dense network of microfilaments