9.2 Intermediate filaments

Question 1

Intermediate filaments are larger than ____ but smaller than ______.

Answer 1

Actin/microtubules

Question 2

What is the principle function of intermediate filaments?

Answer 2

Mechanical strength, structure and integrity to cells

Question 3

Describe an intermediate filament subunit.

Answer 3

• non-polarized
• non-globular
• long alpha helical
• no energy is needed to polymerize the monomer subunits

Question 4

Protofilament

Answer 4

2 tetramer subunits packed together

Question 5

How many protofilaments to form 1 intermediate filament?

Answer 5

8 protofilaments

Question 6

What drug causes rapid disassembly of intermediate filaments in cells?

Answer 6

Nocodazole = causes the IF network to collapse

Question 7

Plectin

Answer 7

Plectin links intermediate filaments to other components of the cell. For example, Plectin links intermediate filaments to microtubules in the cell

Question 8

Alexander disease

Answer 8

Mutation in GFAP protein causes the protein to form dense masses in brain tissue called Rosenthal fibers. This creates the replacement of brain tissue with large fluid-filled cavities

Question 9

How do you disassemble an intermediate filament?

Answer 9

Phosphorylation of the intermediate filament = disassembly

Question 10

What are the 4 types of Intermediate filaments?

Answer 10

1. Nuclear
2. Vimentin-like
3. Epithelial
4. Axonal

Question 11

Intermediate filaments form dense networks that _____.

Answer 11

Run throughout the entire cell

Question 12

Intermediate filaments resist a great deal of ______ and stretch ____ to accommodate the force.

Answer 12

Pulling forces/A lot

Question 13

What is the effect of intermediate filaments being specialized structures on human biology?

Answer 13

If someone has a mutation in any one gene for a type of intermediate filament, this will lead to a defect in only a small number of cell types. As as result, these mutations may not be lethal but can still lead to clinical disease symptoms.

Question 14

What is the structure of intermediate filaments that allows them to be very strong?

Answer 14

The long alpha helical structures of the filaments subunits form protofilaments which are linked together in a staggered pattern. This means the ends don’t line up across a filament. There are many places where interactions with other subunits can form = stronger.

Question 15

Coiled coil

Answer 15

Two alpha helical monomer intermediate filament subunits coiled together in the same direction.

Question 16

Staggered tetramer

Answer 16

2 coiled coil dimers oriented in the opposite direction and staggered

Question 17

Non-phosphorylated IF subunits assemble _______ .

Answer 17

Spontaneously

Question 18

Phosphorylated subunits of IF _______ .

Answer 18

Causes the disassembly of intermediate filaments.

Question 19

Unlike microtubules and actin, intermediate filaments are:

• polarized
• non-polarized

Answer 19

Non-polarized….tetramer has one dimer oriented in one direction and the other dimer oriented in the opposite direction

Question 20

GFAP

Answer 20

Glial Fibrillary acidic protein – a Vimentin-like type of Intermediate filament which is located in the Glial cells (astrocytes and schwann cells of the nervous system)

Question 21

Desmin

Answer 21

Vimentin-like type of intermediate filament that is located in muscle cell sarcomeres

Question 22

Desminopathy

Answer 22

Mutations in desmin and it’s associated proteins cause a variety of muscle disorders. The sarcomeres don’t line up across their muscle cells as nicely as normal cells

Question 23

Rosenthal fibers

Answer 23

Dense mass structures formed when there are defects in the GFAP proteins. A characteristic of Alexander’s disease

Question 24

Epidermolysis bulosa symplex

Answer 24

A condition in which the individual’s skin is easily damaged and forms large blisters due to Keratin genetic deficiencies

Question 25

Lou Gehrig’s disease

Answer 25

Also called ALS (Amyotrophic lateral sclerosis disease) – unnatural mass of tangled neurons caused by a defect in the neurofilaments of the nervous system.