Cell Morph Mot Flashcards
Actin
polymer of single, globular protein, polar (minus and plus ends, grows from the plus end);
In general, how do actin and myosin allow cells to form diff morphologies?
- Crosslinks in diff cells (filamin and fimbrin)
- myosin contraction changes cell shape
- cytokinesis that splits cells performed by myosin and actin
What are the crosslinking proteins of actin and how do they express in certain structures?
- Fimbrin (small, crosslinking protein in microvilli)
- alpha actinin (larger)
- Filamin (X shaped, actin that provides support to cell membrane united by filamins)
Myosin
Responsible for changing cell shape, polar, can move organelles along actin as a single myosin or can form fillaments that contract along with actin in response to a Ca increase in the cells,
Intermediate filaments
predominate in cells that undergo a lot of mechanical stress, extend from nucleus to cell membrane, non polar, dimerize and then tetramerize (NH2——–COOH), lateral interactions give them mechanical strength, no associated motor proteins,
Tissue specific : keratin in skin, lamins
What disease phenotype is associated with mutations in intermediate filaments?
mutations in intermediate filament kerosin can cause blistering
Do cells move randomly or directionally?
Directionally in response to external stimuli
How do cells move?
Push cell membrane, adhere, and pull
Accomplish this through actin polymerization, actin is added at 70 degree angles to old actin polymers and branching, move the cell membrane forward
What is the role of actin nucleating factors in the process of actin polymerization?
Normally, actin polymerization has a lag time as actin monomers unite in units of three, actin nucleating factors (like ARP 2/3) help actin overcome this lag by uniting with actins to form this complex early, this means that actin nucleating factors are a control pt of the regulation of cell movement
How does one stop actin polymerization?
Capping proteins bind to the + end of actin and halt the polymerization
How do you ensure there is enough actin in the monomer state to create new actin filaments?
Need to break down old actin using cofillin
Confillin recognizes actin bound to ADP (actin polymerization bind ATP that is hydrolyzed over time to ADP)
USED IN CANCER DRUGS
How does actin polymerization respond to external stimuli?
External signal bind to a receptor protein and activate WAsP, which activates ARP2/3 actin nucleating factors
in neutrophills that chase bacteria, the bacteria triggers a signal that also activates ARP2/3, when the bacteria move, the transmembrane receptors move to the side of the cell the bacteria is on and grow in that direction
