cell motility

types of cell motility

flagella or cilia dependent swimming, actin dependent migration, and amoeboid motion without actin

anatomy of actin dependent migration

going left to right looking top-down cell tail, nucleus and cell body, the lamella and then the lamellipodium

requirements for cell mobility

ability to sense environmental cues, ability to polarize the cytoskeleton, ability to generate the force to move and the ability to stay on track.

cell polarization changes and the cytoskeleton

the cytoskeleton responds to signals by rapidly changing shape altering the cell polarity

value of yeast as a research tool

easy to get, grow easily, can exhibit sexual and asexual reproduction, most proteins have a human homolog, so they are useful for studying human biology

conjugation/schmoozing

basically yest sex, alpha and beta yeast cells release opposite mating factors which bind to the other cell. this causes the alpha cell to release a mating factor. The mechanism is controled by g-protein coupled receptors.

cell division/budding in yeast

mother cell selects a budding site likely next to an old budding scar and then directs protein complexes for budding to that site which trigger cell division at that site. done in response to internal stimulus

neutrophils

immune cells that polarize in order to track invasive pathogens

keratocytes

epidural cells in fish and some mammals good for studying cell movement since they are big and move fast, change shape based off external cues

chemotaxis

when cells follow gradients of diffusable factors

haptotaxis

when cells follow a gradient of immobilized molecules which are attached to an ecm

durotaxis

when cells follow a gradient in thickness

galvanotaxis

when cells follow a gradient in voltage

profilin

important protein for cell movement forms a complex of proteins. promotes actin growth at the plus end

role of branched actin in cell motility

branch actin will assembly in one part of a cell due to the action of APR complexes. this leads to large amounts of actin polymerization in one spot pushing the membrane forward

neuron cell expansion

neurons expand by sending out growth cones which expand following tropic signals and then the cell body and axon follows.

substrate in cell migration

in cell migration a substrate is a molecule which a cell uses to adhere and exert force

duty cycle

directed polarization of actin in the direction of the signal. then the lamellipodium attaches to the substratum. after this the back of the cell contracts moving it forward.

permissive factors

signals that get a cell ready to move but do not directly tell it where to go

instructive cues

signals that tell a cell where to go

integrins

membrane proteins very important for cell motility, bind to things outside the cell, can be moved ot where they are most needed.

RAC receptors and motility

cause branched actin web in the lamellipodium and less stress fiber formation

RHO gtps and motility

results in more stress fibers integrin clustering and focal adhesion

g-protein activity level and cell motility

the more g-proteins activated the faster and more persistent the cell movement will be, acts on a gradient

optogenetic control of RAC

adding a laser to rac and its effector makes the reaction between the two occur more spontaneously causing the cell to move more

tropic signal

a signal or directional cue telling a cell to go in a certian direction

focal adhesion

large clump of proteins in the ecm which transmits signals and exerts force on the outside surface