Cellular Motility Flashcards
Myosin 1
Has one head, tail binds to cell membrane, head binds to actin, and the direction of the head motion is toward the plus end of actin
Myosin II
Two heads, tail binds to myosin II, head binds to actin, moves toward plus end
Kinesin
Two heads, tail binds to vesicle and head binds to MT, direction of head moves towards plus end
Dynein
Two heads, tail binds to vesicle, head binds to MT and moves toward minus head; moves vesicles from periphery of the cell toward the cell center
How do kinesin and denein move?
hydrolysis of ATP
Dynactin
dynein and the complex holding onto the vesicle- acts as a shock absorber
Axonal transport
the synapse can release a neurotransmitter taken up by the plus end of the axon after which growth factors or whatever are taken back through the axon to the cell body via kinesin;
or the cell body can send vesicles of protein to the synapse via dynein
gliding
myosin heads immobilized, actin filaments moving over;
MT can also be moved over the motor
ameboid movement
based on actin, MT, and focal adhesions; move via actin polymerization- cell makes attachments to substrates via focal adhesions; the cell then has actin polymerize at the growing edge of the cell (lamellapodia) and at the back edge there is loss of focal adhesions and movement of unpolymerized actin
lamellopodia
plus end of the cell moving in a wave like form;
in a moving cell actin is concentrated where?
in the edge; right behind the concentrated actin is actin+cofilin which modifies the actin and disassembles it so that the cell can move forward
focal adhesions
integrins consisting of two subunits: alpha and beta- both going through the plasma membrane and binding to extracellular matrix and the internal cytoskeleton
alpha subunit of integrin
two chains linked by a disulfide linkae and a globular head with binding sites for divalent cations
beta subunit of integrin
cytoskeleton side binds to vinculin, a-actinin, and talin which then bind to actin; extracellular side is rich in cysteine regions and binds to RGD domain (arginine, glycine, aspartic acid) on laminin and fibronectin
focal adhesion complex activation
focal adhesion kinase can be activated to increase size of the focal adhesion complex;
focal adhesion connection importance
connection to the matrix gives cell “traction” for movement and is a signalling complex that will alter intracellular environment
How are MT brought to FA
by elongation or by motors; when MT touches FA, the GTP cap is destabilized and MT retracts by depolymerizing
interaction between actin and MT-TCx will cause focal adhesion molecules to
disappear
What happens once the MT binds to FA
this signals destabilization of the microtubules, and the microtubule also causes the disruption of the focal adhesion
where are focal adhesions located
where actin filaments are attached to the cell membrane
how do melanoma cells metastasize?
through the basement membrane by expressing many MMPs and demodeling the ECM to burrow through the basal lamina; they can then move throughout the body via the circulatory system and metastasize in liver and heart
MMP
degradation of ECM during normal cell growth, turnover, etc.
MMPs are involved in
embryonic development, tissue morphogenesis, wound repair, inflammatory diseases, cancer
what type of collagen is degraded by MMP-2
Type IV collagen (a major component of basement membranes)
