Cytoskeleton Flashcards
Ch 17, Ch 20
What are the 3 types of epithelial junctions?
tight, adherens, desmosomes
What is a tight junction?
a barrier between cells which prevents non-specific fluid transport
What is an adherens junction?
forece bearing adhesion which links cadherins and actin, they support tight junctions
What are cadherins?
kind of adhesion proteins which bind to the same cadherins (ie homophilic) on adjacent cells, and the underlying skeleton
What are desmosomes
provide mechanical structure of cell, they connect keratin from the cell to plaques on the inside edge of cells which can interact with plaques from other cells
What are intermediate filaments?
proteins which form long strings of 8 tetramers twisted together
What are simple epithelia?
single layer of epithelial cells, all cells are in contact with basal lamina
What are stratified epithelia?
multilayer of cells, not all cells contact basal lamina
What kind of epithelia is skin?
stratified, keratin layer on top of epithelia makes skin impenetrable
What is Epidermolysis Bullosa Simplex? What is it caused by?
A family of skin diseases associated with keratin mutations, Keratin makes bumpy folds with epithelia instead of being sealed
What are the different classes of intermediate filaments?
Keratin, vimetin, neurofilaments
Where are keratin filaments found?
epithelial cells
Where are vimentin filaments found?
connective tissue, muscle cells, glial cells
Where are neurofilaments found?
nerve cells
What are nuclear lamins? where are they found?
filaments which provide additional mechanical support in the nucleaus - it is located between the nuclear membrane and chromatin in the nucleus in all animal cells
What is progeria?
Disease which causes children to age really fast, point mutation creates an early splice site which makes lamins too short to be clipped in nuclear envelope so they build up a lot
Describe lamin A production
Lamin a protein and farnesyl bind outside the nuclear envelop and travel inside the nucleus where it binds to the nuclear membrane, the farnesyl group is clipped off and the lamina is incorporated into the nuclear lamina.
What is actin treadmilling?
???
What does phalloidin to do actin?
binds and stabilizes filaments
What does cytochalasin do to actin?
caps filament plus ends, prevents polymerization at that end
What does latrunculin do to actin?
binda actin monomers and prevents their polymerization
What are the possible shapes of actin filaments?
microvili - increase membrane surface area
contractile bundles - stress fibres linked to focal adhesions
cellular protrusions - help cell migration
contractile ring - cell division
What Rho GTPases make each type of actin?
RhoA -> actin stress fibres (contractile bundles)
Rac1 -> lamellipodia (cellular protrusions)
Cdc42 -> filipodia (cellular protrusions)
How do actin filaments become specific?
the proteins which bind to them and organize them in ways to perform a certain function
