04a: Cytoskeleton Flashcards
Roles of cytoskeleton
- Structural scaffold
- Cell movement
- Intracellular traffic
- Mitosis and meiosis
How can targeting cytoskeleton be a method to treat cancer?
- Cell movement (metastasis)
- Cell division (proliferation)
Depend on cytoskeleton
T/F: cell motility only dependent on actin.
False - MT also play a role
Roles of MT:
Mitosis, motility, intracellular transport, secretion, cell shape/polarization
Basic MT structure:
Long, hollow cylinder
MT polymers are composed of (X) (monomers/dimers/trimers/other).
X = alpha and beta tubulin
Hererodumers
There are how many isoforms of alpha and beta tubulin?
3 forms of alpha and 5 forms of beta
Which structural component is responsible for the polarity of MT?
The head-to-tail association of the heterodimers
(X) nucleate the MT at its (Y) end, and the MT begins to grow.
X = centrosome Y = minus
Which end of MT grows?
Both plus and minus ends grow. But different rates of polymerization.
Beta tubulin points to (X) end of MT. Alpha tubulin points to (Y) end.
X = plus (faster-growing) Y = minus (slower-growing)
Gamma-tubulin is important for (MT/actin) formation. What’s its function?
MT; functions as template for correct MT assembly
(X) proteins bind to MT for what purpose?
X = capping
Stabilization
Capping proteins bind to (alpha/beta) tubulin.
Neither! Gamma-tubulin
MT regulation depends on:
- Proteins
2. Properties (isoforms and post-translational modifications)
Taxol function.
Stabilizes MT; drug against a number of cancers
Colchicine function.
Binds MT subunits and prevents polymerization
Vinblastine function.
Binds ends of MT subunits and prevents polymerization.
T/F: taxol, colchicine, and vinblastine are all chemotherapeutics.
False - colchicine used to treat gout and femial Mediterranean fever
Intermediate filaments important for:
- Mechanical integrity
2. Active sequestering, positioning, scaffolds for signal molecules
Intermediate filaments are divided into (X) classes, based on:
X = 6
Specific cell type in which filaments are found
Acidic keratin intermediate filaments play role in which cell type?
Epithelia
Desmin intermediate filaments play role in which cell type?
Muscle
Lamin intermediate filaments play role in which cell type?
Cell nuclei
Actin filaments, aka (X), are important for:
X = microfilaments
- Cell shape
- Locomotion
- Muscle contraction
- Cytokinesis
- Phagocytosis
- Platelet aggregation
What’s the structure of actin polymer?
Two-stranded helix of actin monomers
What are the types of actin monomers?
Alpha, beta, gamma
An actin filament typically contains (X)% alpha monomer, (Y)% beta, (X)% gamma.
Each filament contains only one type of actin
Which end of actin grows?
Both! But different rates of polymerization
The basic requirements for a cell to move:
- Change shape
- Create traction/force
- Balance attachment and detachment to ECM
- Move in a direction
T/F: all steps required for cell locomotion involve the actin cytoskeleton.
True
List the steps of cell locomotion.
- Protrusion of leading edge
- Adhesion at leading edge and detachment at trailing edge
- Movement of cell body
Leading edge of cell protrudes in response to (X), such as:
X = Extracellular signal
- Growth factors
- AA or formylated peptides
- Second messengers
Detection of signal for cell movement will cause which intracellular event?
Activation of Rho GTPase Rac1 as well as PIP2
Action of Rac1/PIP2
Activates WASP family/Scar
(WAVE/WASP) is part of the (WAVE/WASP) family.
WAVE; WASP
WAVE function.
Activated Arp2/3 complex
Arp2/3 complex function
Actin nucleation (new filaments initiated)
ADF/cofilin complex function
Severs/depolymerizes ends of existing actin filaments during protrusion of leading edge
In protrusion of leading edge, (X) engulfs the severed actin subunits and breaks them down into (Y).
Actin units are bound to profiling and recycled for new filaments
During protrusion of leading edge, prevention of further actin extension is done by:
Capping the plus ends by Formin proteins
T/F: Actin polymerization generates branched 3D network and pushes membrane forward.
False - 2D network
Attachment of leading edge to (X) is possible by:
X = ECM
Actin interaction with integrins
Detachment of trailing edge is carried out by:
Rho A (a Rho GTPase)
(Alpha/beta) integrins interact with actin cytoskeleton.
Both alpha and beta
Which key mechanisms allow cell body movement?
- Actomyosin contraction
2. Molecular clutching
Actomyosin contraction involves which type of myosin.
Non-muscle myosin II
Which myosin domain is responsible for movement down (X) filaments?
X = actin
Globular head domain
In actomyosin contraction, the myosin functions as (monomer/dimer/trimer/other).
Form bipolar filaments, with globular heads on opposite sides.
Myosin moves toward (X) end of (Y) during actomyosin contraction
X = plus Y = actin filaments
In locomotion, which part(s) of cell body movement require(s) ATP?
Hydrolysis of 1 ATP required for myosin conformational change that moves protein along actin filaments
When molecular clutch (engaged/disengaged), actin cytoskeleton is anchored to (X).
Engaged;
X = ECM
Integrins serve which function(s)?
- Sites of adhesion for actin cytoskeleton
2. Signaling centers (regulate Rho GTPases)
