Cytoskeleton and Response to Mechanical Stress Flashcards
Cytosol
- inside of a cell
- surrounds organelles
- microscopy has reveled it’s highly structured
Cytoskeleton
- skeleton of cell
- complex network of interconnected filaments and tubules
- extends throughout cytosol
- attaches to inner surface of plasma membrane
What does cytoskeleton play a role in?
- cell movement
- cell division
- internal organization
- cell signaling
- cell adhesion
Major Structural Elements of Cytoskeleton
- Microtubules
- Microfilaments
- Intermediate Fibers
What are the structural elements of cytoskeleton in order of increasing size?
- microfilaments (7nm diameter)
- intermediate filaments (8-12nm diameter)
- microtubules (25nm diameter)
Microtubules
- largest (outside diameter 25 nm; inside diameter 15 nm)
- varying length
- hollow, straight cynlinders
- wall consists of protofilaments = 13 arranged side-by-side that form hollow center
- functions
- cellular movement = flagella and cilia
- maintenance of nerves and axons
- spatial orientation in cytosol = govern location of organelles
Protofilament
- heterodimer of tubulin
- alpha-tubulin
- beta-tubulin
Microtubule Associated Proteins (MAPs)
- bind at regular intervals along wall of microtubule
- allows interaction w/ other filaments
- regulate growth of microtubule
In Alzheimer’s, what happens in relation to microtubules?
The protein tau becomes tangled and causes the microtubule to become instable and fall apart. This destroys nerve communication and neuron loses shape and dies.
Microfilaments
- smallest cytoskeleton elements
- Roles:
- contractile fibers of muscle cells
- occur in almost all eukaryotic cells
- make up cell cortex = dense network of microfilaments attached to inncer face of plasma membrane
- important in shape of cell
Actin
- building block of microfilamets
- extremely abundant in virtually all cells
- Nomenclature
- G-Actin = individual Actin
- F-Actin (Filamentous) = polymerization of G-Actin
- Two Major groups
- Muscle-specific = alpha-actin
- Non-muscle = beta-actin and gamma-actin
Functions of Actin-Binding Proteins
- stabilizes filaments
- generate force
Intermediate Filaments
- Size between microfilaments and microtubules (8-12nm diameter)
- Role: structure and tension-bearing
- Most Stable
- Least Soluble
- Scaffold that supports entire cytoskeleton
How many classes of intermediate filaments are there?
6 Classes.
I and II = Epithelial cells III = muscle, glial, CT IV = nerve cells V = All cells VI = embryonic nervous system
When is mechanical stress important?
- Normal Physiological Processes
- cell growth
- function
- differentiation
- apoptosis
- Pathology
- heart disease
- lung disease
Mechanical stress adaptations occur via changes in…
- structure
- metabolism
- gene expression
Tensegrity structure
- tensegrity = combination of tensional integrity
- uses tension (pull) and compression (push) to provide support
Cytoskeleton and Tensegrity
Microfilaments generate tension
Microtubules are compression bearing
Intermediate filaments provide elasticity
Transmitting Stress in the Cytoskeleton
- transmits stress from 1 point to rest of structure
- adapts so that tension bearing forces align with direction of stress
Responses to stress
- Outside-In signaling = ECM recognizes stress, transmits signal into cell, cell can adapt as needed
- Regulation of nuclear access = altering pore size leading to nucleus
- adaptation of cytoskeleton and ECM =confirmational change -> allows for adaptation to stress
