Why are cytoskeletons dynamic and adaptable?
Can disassemble, diffuse, and reassemble elsewhere
What forms of cytoskeleton filaments are thermally stable?
Single protofilament are not thermally stable
What filaments are resistant to stretching forces?
What are the main components of cytoskeletal filaments?
Mesh-like structure made up of intermediate filaments.
Fuctions of intermediate filaments
Form a network throughout the cytoplasm and surround the nucleus
Rope-like properties give high tensile strength
Often further stabilized by accessory proteins
– Cross-link filaments into bundles
– Link to microtubules, actin filaments, and cell-junctions
What intermediate filament is found in epithelial cells?
What intermediate filament is found in connective tissue cells, muscle cells, and glial cells?
Vimentin and vimentin-related filaments
What intermediate filament is found in nerve cells?
What is the nuclear intermediate filament?
Functions of microtubules
Provide tracks for transport vesicles
Mitotic Spindle formation
Cilia and Flagella
Binds and stabilizes microtubules
Binds tubulin dimers and prevents polymerization.
Colchicine, colcemid, vinblastine, vincristine
What is F actin composed of?
Twisted polymer of G-actin (globular) that has structural polarity
Many must be in association with other proteins to be stable
Binds and stabilizes actin filaments
Caps actin filament plus end, preventing polymerization there
Binds actin monomoers and prevents polymerization
How can actin filaments be modified when bonded to other proteins?
What are some extracellular proteins?
Sheet formin collagen (IV)
Fibrillar collagen (I,II,III)
Main structural protein in ECM/connective tissue and basal laminae.
How do collagen types differ?
Form collagenous triple helix
Can be fibers, sheets, or transmembrane structures
Where is the precollagen prepared for secretion
Scurvy is caused by loss of what cofactors
Ascorbate or Iron
Disease caused by defects in collagen or enzymes contributing to synthesis.
Weakens connective tissue in the skin, bones, blood vessels, and organs
Links cells to extracellular matrix, or basil lamina
What are the four classes of Cell Adhesion Molecules
Ig-superfamily CAMs (NCAM)
What are the common aspects of cadherins?
Ca2+ dependent adhesion molecule – Important in formation of junctions between cells (epithelial “sheets”) such as desmosomes and adherens junctions
– Homophilic interactions (extracelluar)
– Interact with cytoskeleton (actin)
What are classic cadherins?
Cytoplasmic domain interacts with beta-catenin, alpha-catenin, and p120
Linked to the actin cytoskeleton
Associated with adherens junctions
What are the classic cadherin examples listed?
What are atypical cadherins?
Function without interaction with catenins or a link to the actin cytoskeleton.