Cytoskeleton: Microtubules

Question 1

three types of cytoskeletal filaments in the cell

Answer 1

microtubules, microfilaments (also know as actin) and intermediate filaments

Question 2

microtubules

Answer 2

1 of the 3 types of cytoskeletal filaments in the cell, can be thought of as the “bones” of the cell. Function: maintain cell shape, rigidity and structure, as well as transport of cargo and cell division.

Question 3

alpha and beta tubulin

Answer 3

the two proteins that make a dimer that is the microtubule building block

Question 4

protofilament

Answer 4

alpha and beta tubulin dimers stack one on top of another in in head to tail orientation to produce this, polarized

Question 5

13

Answer 5

of protofilaments that assemble into each hollow microtubule

Question 6

alpha tubulin

Answer 6

the end of a microtubule with exposed ___ ___ is considered the negative (minus) end of the molecule

Question 7

beta tubulin

Answer 7

the end of a microtubule with exposed ___ _____ is considered the positive (plus) end of the molecule

Question 8

Gamma tubulin ring complex (or microtubule organizing center [MTOC])

Answer 8

microtubules are nucleated from these sites, which are located in the centrosome (close to the nucleus). These sites function to help alpha and beta tubulin dimers to associate into filaments.

Question 9

dynamic instability

Answer 9

in order for cells to function properly, microtubules need to be able to change shape, grow (rescue), and shrink (catastrophe). This concept is known as

Question 10

GTP cap

Answer 10

a growing microtubule has this, which stabilizes the microtubule and allows for continued adding of dimers. When growing slows down or stops, you eventually get a microtubule without this because even the most distal alpha-beta dimers have hydrolyzed GTP

Question 11

kinesins

Answer 11

motor proteins that move cargo toward the (+) end of the microtubule (beta end), and thus to the periphery of the cell

-when bound to ATP, has increased affinity for microtubule track; when unbound, lower affinity for track

Question 12

dyneins

Answer 12

motor proteins that move cargo toward the (-) end of the microtubule (alpha end), and thus toward the nucleus/interior of cell. These are much larger, consist of many subunits, and require regulatory complexes for function, which has limited our ability to study them

Question 13

axonemal dynein

Answer 13

found exclusively within cilia and the flagellum, the microtubules themselves are the cargo - sliding them against each other allows for bending and power stroke

Question 14

cilia

Answer 14

small finger-like protrusions from cell surfaces, found on epithelial linings to generate waves that move mucous down the respiratory tract, has 9+2 microtubule structure

Question 15

primary ciliary dyskinesia (PCD)

Answer 15

disease that causes motile cilia to be defective = airway epithelia movement defective, buildup of mucus and increased risk of infection, sperm motility defective, cilia of female reproductive track defective - infertility

Question 16

primary cilium

Answer 16

non-motile cilium, has 9+0 organization, function in mechanosensation and cell signaling, most cells have 1 on surface.

Question 17

polycystic kidney disease (PKD)

Answer 17

disorder of primary cilium function that results in kidneys being unable to sense flow, unable to properly filter urine, = kidney failure

Question 18

Bardet-Biedl syndrome (BBS)

Answer 18

relatively rare disorder of the primary cilium, symptoms of the disease include ocular defects, polydactyly, defective kidney function and weight gain. Some behavioral and cognitive abnormalities are also observed.

Question 19

Lissencephaly

Answer 19

disorder of microtubule organization that causes cargo buildup on neuronal axons, causing defective transmission of impulses. Symptoms: smooth brain, seizures, muscle spasms, dysphagia, psychomotor retardation. Arises due to mutation or loss of 1 copy of Lis1 which regulates dynein.

Question 20

dynactin complex

Answer 20

regulator of the dynein motor, helps the dynein motor load onto the tracks. One component of the complex is encoded on Dctn1 - if mutations arise, leads to Perry syndrome or distal spinal and bulbar muscular atrophy

Question 21

Perry syndrome

Answer 21

autosomal dominant disease resulting from mutations within the microtubule binding region of Dctn1. Symptoms usually present late in life.
Symptoms: tremors, weight loss, depression

Question 22

Distal spinal and bulbar muscular atrophy

Answer 22

a motor neuron disease caused by mutations in the binding region of Dctn1. Symptoms present earlier than the other disease. Symptoms: muscle weakness, muscle atrophy, motor deficits

Question 23

vinblastine

Answer 23

drug used in cancer treatment in low doses, destabilizes microtubules thus killing cells undergoing replication

Question 24

taxol

Answer 24

drug used in cancer treatment in low doses, stabilizes microtubules which causes them to be rigid, cells undergoing mitosis will die

Question 25

tau

Answer 25

microtubule binding protein that stabilizes microtubules under normal conditions; implicated in Alzheimers for forming aggregates and losing its ability to bind microtubules after being hyperphosphorylated