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Cell biology > Intermediate filaments > Flashcards

Intermediate filaments Flashcards

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1
Q

Which types of animals have intermediate filaments (IFs)?

A

Vertebrates and soft bodied metazoans, all animals but sponges.

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2
Q

What function do intermediate cells have? Given that, where are they likely to be found in abundance?

A

They are structural rope like structures, they are extremely strong. They are fond in cells under a great deal of mechanical stress.

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3
Q

What gives the structural strength to cells in tendons and ligaments?

A

The intermediate filaments.

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4
Q

How many kinds of IFs do insects have? Why?

A

1 type, they have chitin to provide structural support.

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5
Q

Keratin is made of what?

A

Keratin is the IFs found in claws, skin, and hair. Repeat Keratin is intermediate filaments

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6
Q

Where are IFs found?

A

The cytoplasm and the nucleus

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7
Q

What is Vimentin?

A

An intermediate filament in the cytosol (cytosolic skeleton)

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8
Q

Lamin B (or any other lamin) found where do what?

A

Nucleus, they are part of the nuclear lamina. An IF structure that provides integrity to the nucleus and is involved in regulation of cell cycle through phosphorylation.

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9
Q 
What size is...
Intermediate filaments
Actin
Microtubules
myosin
A

Intermediate filaments: 10 nM
Actin: 7-9 nM
Microtubules: 25 nM
myosin 20 nM

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10
Q

what else are IFs known as?

A

Nano filaments.

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11
Q

Go through Intermediate filament formation

A
  • Monomers have alpha helices.
  • A monomer raps around another in a parallel coiled coil arrangement, forming a dimer
  • A dimer aligns slightly offset, by another dimer, in an antiparallel arrangment forming a tetramer
  • 8 tetramers twist together to form a rope type filament
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12
Q

What type of contact lateral or lengthwise dominate in intermediate filaments?

A

Intermediate filaments will contact the filaments running alongside them far more then those next to them, but since they are staggered, they are all strongly interconnected.

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13
Q

Rank in terms of stress befroe fu
actin
microtubules
intermediate

A

actin: 33
microtubules ruptures: 3
intermediate: 60 not yet ruptured

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14
Q

What types of proteins do IFs have?

A

They have cross-linking and bundling proteins.

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15
Q

which types of proteins do they lack?

A

They lack nucleating, sequestering, capping, and severing proteins.

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16
Q

IFs are organized into higher order structures called ______, which is achieved by using ______. This increases strength and stability.

A

Strong arrays.

Crosslinking and bundling proteins.

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17
Q

Neurofilaments NF-M and NF-H do what differently then normal IFs?

A

They have an elongated C terminus, which binds to neighbors allowing them to self bundle.
Specific to nerve cells.

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18
Q

Name two major accessory proteins for IFs and what they interact with.

A

Filaggrin: keratin

Plectin: vimentin

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19
Q

What does Filaggrin do?

A

Is likely a bundling protein which binds keratin, helps increase toughness of skin, which has a lot of keratin.

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20
Q

What does plectin do?

A

Plectin bundles vimentin by cross-linking the filaments. Mutations of plectin can be lethal.

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21
Q

Can IFs be modified after they are constructed?

A

No. They are stable once constructed, which is a major difference between IFs and microtubules and actin.

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22
Q

What does it mean when I say that IFs are more heterogenous then actin and microtubules?

A

There are more kinds of IFs.

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23
Q 
Do IFs?
Interact with motor proteins?
Have intrinsic polarity?
Bind ATP or GTP?
Have enzymatic function?
A 
Interact with motor proteins?
No
Have intrinsic polarity?
No
Bind ATP or GTP?
No
Have enzymatic function?
No
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24
Q

How many genes encode for IFs? How many disorders are associated with defects in IFs?

A

70 genes.

40 disorders.

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25
Q

Four broad types of IFs

A

Nuclear
Vimentin Like
Epithelial
Axonal

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26
Q

Nuclear IFs

A

Lamins A, B, C inner lining of nucleus

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27
Q

Vimentin Like IFs

A

Vimentin Mesenchymal orgin cells
Desmin Muscle
Glial Fibrillary glial cells (scwann cells etc)

28
Q

Epithelial IFs

A

type I keratin (acid) epithelial…

type 2 keratin (base)

29
Q

Axonal IFs

A

NF-L, NF-M, NF-H Neurons

30
Q

What are mesenchymal cells?

A

Stem cells which can become osteocytes, adipocytes, myocytes, and chondrocytes (cartilage cells)

31
Q

How are intermediate filaments classified?

A

As belonging to 1 of six sequence homology groups

32
Q

IF homology
Type I
Type 2

A

Form obligate heterodimers. Keratins
Type I acidic
Type 2 basic

33
Q

How many genes encode for keratins?

A

50

34
Q

What are the two main isoforms of Keratin?

A

Epithelial keratins

Trichocytic keratins

35
Q

Epidermolysis Bullosa Simplix (EBS) results from mutations in what type of IFs?

A

Epithelial Keratins Keratin 5 and 14.

36
Q

Epidermolysis Bullosa Simplix (EBS) has what symptoms caused by what?

A

Blistering due to fragile skin tissue which is fragile because keratin 5 and 14 are mutated.

37
Q

What do N and C termini mediate (at least in keratin, maybe all IFs)?

A

Mediate laterally binding between adjacent Keratin filaments.

38
Q

What happens when you mutate a mouse so that it lacks N and C termini for its Keratin?

A

Due to the fact that N and C termini are the means by which lateral linkage between filaments is achieved, the cytoskeleton will fail in a manor similar to EBS.

39
Q

Explain what the basal lamina is and how it interacts with epidermal cells.

A

The basal lamina, is the lamina which the skin grows from.
Epithelial cells are anchored through a IF network to hemidesmosomes (build partially of desmin?).
bottom layer of skin cells are anchored to the basal lamina, all cells on type are anchored to the cells beneath and around them. If keratin networks are defective they will not anchor well and the skin will shear, breaking the epidermis from the lamina.

40
Q

Trichocytic keratins

A

Are what makes up hair, fur, claws, fingernails, bird beaks, rhino horns, reptilian scales, and avian feathers.

41
Q

Trichocytic keratin networks have what distinctive bonding type?
How much of hair’s dry weight is keratin?

A

Disulfide cysteine-cysteine bonds.

> 90%

42
Q

Trichocytic keratin networks have what distinctive bonding type?
How much of hair’s dry weight is keratin?

A

Disulfide cysteine-cysteine bonds.

> 90%

43
Q

Type III IFs are?

A

Vimentin like IFs

  • Vimentin
  • Glial fibrillary acidic proteins (GFAP)
  • Peripherin
  • Desmin
44
Q

Where are the following found

- Vimentin

A
  • Vimentin:
    found in mesochymal cells. chondrocytes, osteocytes, fibrocytes, myocytes, neuroglial cells, endothelial blood vessel cells, leukocytes (immune cells)
45
Q

Where are the following found

- Glial fibrillary acidic proteins (GFAP)

A
  • Glial fibrillary acidic proteins (GFAP):

Astrocytes (central nervous glial cells) and some schwann cells (peripheral nervous glial)

46
Q

Where are the following found

- Peripherin

A
  • Peripherin: Found in some peripheral neurons, NOT glial cells.
47
Q

Where are the following found

- Desmin

A
  • Desmin: a structural component of muscle cells (myocytes)
48
Q

Type IV IFs are what?

A

Neurofilaments

found in axons. They convey longitudinal (length wise) tension. Help establish diameter of the axon.

49
Q

What are the three subtypes in type IV?

A

NF-L light neurofilaments
NF-M medium neurofilaments
NF-H heavy neurofilaments

50
Q

What is amyotrophic lateral sclerosis (ALS)?

A

Progressive neurodegeneration of the motor neurons. in the brain and spinal cord. Eventually can lead to paralysis or death as motor neurons die.

51
Q

What is sclerosis?

A

Abnormal hardening of a body tissue.

52
Q

What is one proposed cause for ALS?

A

The disease is associated with an accumulation of abnormal (type IV) neurofilaments, which could have caused cell death through interference with axonal transport. But might not have.

53
Q

What is one major difference between Type III Glial IF and type IV neuro?

A

Type IV has much more crosslinking then Type III does.

54
Q

Type V Lamins

A

Most ancient, believed that it is the ancestral type. Found in the nucleus.

55
Q

Type VI

A

Eye lens IF

56
Q

What are the Eye lens IF proteins?

A

Filensin/CP115

CP49/phakinin

57
Q

Muscular distrophy

A

A class of diseases which cause progressive skeletal muscle weakness. most MD’s are likely X-linked recessive (mostly affect males, female carriers)

58
Q

How many causes does Emery-Driefuss muscular dystrophy (EDMS)

A

Has two different causes

59
Q

Autosomal-dominant EDMD occurs because?

A

LMNA gene mutation affecting Lamin A and Lamin C

60
Q

X-linked EDMD occurs because?

A

mutation of Emerin, a Lamin binding protein

61
Q

Most LMNA (lamin encoding genes) that lead to muscular distrophy still result in a protein product. It is just structurally different. Why is this?

A

This is likely because the production of no Lamin would be lethal imediately to the cell. You would have no Lamina and likely no nucleus… Not good in a world were gene regulation is what it is. I’m not sure if this would also affect the Endoplasmic reticulum formation directly.

62
Q

What is Hutchinson-Gilford Progeria syndrome caused by?

A

Mutations in nuclear lamins. Gives aberrant morphology.

63
Q

Dilated cardiomyopathy can be caused by mutations in ______.

What are the symptoms of this disease?

A

Cells in heart can no longer adhere to each other as well. Contractile strength begins to fail.

64
Q

Acrylamide?

A

Is a toxin that causes disassembly or rearrangement of intermediate filaments networks.

65
Q

Acrylamide is found in…

A 
Page
Coffee
Potato chips
french fries
it is responsible for browning.
Carcinogenic neurotoxin.
66
Q

Acrylamide and the maillard reaction

A

This reaction causes browning and forms acrylamide.

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