Cytoskeleton Flashcards
May exist as single filaments (7-8nm diameter), in bundles, or in networks.
Found in most cells. Helps establish a cytoplasmic protein framework radiating from nucleus to plasma membrane.
Polar (+ and - ends)
Consist of proteins G and F
Requires ATP for polymeraization
Microfilaments (Actin Filaments)
Free actin in the cytoplasm
G-actin
Polymerized actin in a filament.
Helical arrangement of two chains
F-actin
Anchorage and movement of membrane proteins
Structural core of microvilli & stereocilia
Extension of cell processes
Cell motility - Locomotion without flagella
Controls the physical nature of the cytosol (aggregation of this increases viscosity while dispersion decreases it)
Microfilaments (Actin)
Terminal web - a network of actin filaments found along the apical surface of cells.
-Provides framework for cell, attachment of microvilli and basal bodies
-Also found in less organized manner close to cell membrane where desmosome, hemidesmosomes, and zonal adherens are located.
Cytoplasmic extensions on the apical surface of some epithelium that increase the surface
area for absorption.
Non-motile
Consists of a core of actin filaments anchored to the terminal web (actin cytoskeleton network that sits just deep to the plasma membrane)
Microfilaments - Microvilli and stereocilia
Cylindrical, membrane-bound cytoplasmic projections
1-3 micrometers (um) in length
Core of 25-30 actin Microfilaments
-cross linked by villin
-anchored into the terminal web
Microvilli
Shorter rounder protrusions.
Usually long microvilli - up to 120 micrometers (um) in length
Limited distribution
-epididymis (duct in the testes)
-Proximal ductus deferens
-Sensory hair cells of inner ear
Locations needed for much more absorption at quick pace
Stereocilia
Longer protrusions
ATP hydrolyzing motor protein
• Have a head domain that interacts with F-actin and a tail
containing an ATP-binding site • Interacts with actin in a cyclical manner
• Bind – hydrolyze ATP to ADP – detaches – binds again ….Repeats
• The tail can also bind to cellular structures and pull them along the actin filament
• It interacts with F-actinin the cell cortex to stiffen and prevent deformation of the plasma membrane • Actin interaction is responsible for closure of the gaps in wounds
• Actin interaction is responsible for creating the contractile ring that closes of and ultimately pinch two cells that are dividing from each other
•Also plays an active role in skeletal muscle contraction
Myosin
an Actin motor protein
Cell movement
Finger like projections
Core of long, bundled actin filaments
Filopodia
Fingers to Filidelphia
Cell movement
Sheet-like structures
Fibroblasts
Lamellipodia
Wearing a sheet to go as a ghost for Halloween and stand on podium is lame
Cell movement
White blood cells
3 dimensional projections
Pseudopodia
Cell movement
Step 1; before Attachment and Contraction
Actin polymerization at plus (+) end protrudes lamellipodium
Protrusion
Cell movement
Step 2; after Protrusion and before contraction
Focal adhesions anchor the actin cytoskeleton to the extracellular matrix via integrity proteins
Attachment
Cell movement
Step 3; after Protrusion and attachment
Bulk of the trailing cell & cytoplasm is drawn forward
Contraction
Microtubule Poison
Treatment of gout
-Binds to unpolymerized tubular molecules
-Preventing polymerization
-Prevent release of inflammatory initiators (vesicles)
Colchicine
Microtubule poison
Inhibits the formation of mitosis spindle
Inhibits uncontrolled cell division
Targets cancer cells
Vinblastine and Vincristine
Blasted by a tubule.
Microtubule poison
Stabilizes and prevents Microtubule disassembly
Arrests dividing cells in mitosis
Triggers apoptosis
Taxol (Paclitaxel)
Pay a tax if you want to disassemble.
Actin (microfilament) Toxins
Binds to F actin more tightly than G actin
Promotes excessive polymerization and inhibits depolymerization
Inhibits cell movement
Apoptosis
Phalloidin (toxin found in Amanita phalloided - death cap mushrooms)’
Remember: Phil, just talks and polymerizes the conversation, never lets anyone disassemble it.
Actin (Microfilament) Toxin
Block polymerization of actin
Can be used to inhibit cell movement, division, & induce programmed cell death
For study purposes
Cytochalasins
It’s a sin to build actin in chalafornia sites (cytes)
