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40 Cards in this Set

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What are the roes of an intermediate filament?

1. Sustaining stresses and strains


2. Connecting plasma membrane and nuclear compartments


3. Tissue integrity

Are intermediate filaments polar?

No

What cells express intermediate filaments?

Prominent in cells subjected to mechanical stress

Within a cell what distinctions between intermediate filaments are there?

Cytoplasmic and nuclear distinc filaments

What is the main role of cytoplasmic cytoskeletal links?

Mechanical stabilisers and integrators of the cytoskeleton

What are IFAPs?


Give an example of one.

IFAPs link microtubules and actin filaments to IFs and also link IFs to each other


e.g Plectin

What are the types of intermediate filament?

Types I - VI

What specific intermediate filaments fall under Type I & II?

Keratins



What specific intermediate filaments fall under Type III?

Vimentin & Desmin

What specific intermediate filaments fall under Type IV?

Neurofilaments

What specific intermediate filaments fall under Type V

Laminins

What types of Neurofilaments are there?

NF: L / M / H

Where are keratins found?


What type of polymer are they?

In epithelial cells


Heteropolymers

Where are Neurofilaments found?


What type of polymer are they?

Neurons


Homo or heteropolymers

Where are vimentins and desmins found found?


What type of polymer are they?

1. i) Mesenchyme


ii) muscle


iii) glial cells


iv) astrocytes




2. Homo and heteropolymers

Where are laminins found?


What type of polymer are they?

Nuclei of cells


Homopolymers

Describe the molecular structure of a general intermediate filament.

Amino head terminal and Carboxy tail terminal with a central alpha helical rod domain.

Critical motifs: 1A, 1B, 2A & 2B which are similar across all IFs.

Amino head terminal and Carboxy tail terminal with a central alpha helical rod domain.




Critical motifs: 1A, 1B, 2A & 2B which are similar across all IFs.

What are the roles of the amino terminal head and Carboxy terminal tail terminals in an intermediate filament?

1. Amino head is essential for filament assembly


2. Carboxy tail contributes to filament assembly

Describe the assembly process of an intermediate filament.

1. Unstable monomers interact to form a stable parallel, in register, coiled dimer


2. Dimers form staggered anti parallel tetramers - the fundamental subunit


3. Tetramers associate laterally to form loosely packed filaments - protofilaments


4. Further longitudinal extension and radial compaction

What is the length of a typical intermediate filament?

10-14 nm

What is the fundamental regulation system of IF assembly?

Phosphorylation of the serine residues in the amino terminal head domain leads to disassembly

What is the most diverse network of intermediate filaments?

Keratin filaments

What are the subdivisions of keratin filaments?


How do the types interact?

Type I - acidic


Type II - basic / neutral


Form heterodimers

Where can the diversity of keratin filaments be observed?

Diversity is most pronounced in the skin

What do keratin filaments attach to?


What does this help form?

Specialised cell junctions - desmosomes.


Desmosomes provide link between cells to allow keratin to form a continuous network throughout the epithelium.

What keratins are expressed in development?

K8 and K18

What are the cell layers of the skin epidermis?

1. Basal


2. Suprabasal


3. Granular

What keratin types are present in the basal cell layer?

K5, K14 and K15

What keratin types are present in the suprabasal cell layer?

K1 and K10

What keratin types are present in the granular cell layer?

K2e

How does the keratin expression in skin change upon injury?

K10 is swapped out for K16

What is EBS?


What is its molecular basis?

Epidermolysis bullosa simplex (EBS)


Mutations in basal layer keratins - K5 and K14

What is the inheritence of epidermolysis bullosa simplex?

Autosomal dominant

What are the symptoms of EBS?

Disruption of the keratin network causes cellular rupture and thus blistering of the skin

Describe the molecular structure of a neurofilament?

Triplet protein composed of:


NF-L


NF-M


NF-H

What types of IF are found in the nucleus?

A and B type laminins

What is the difference in expression between A and B laminins?

A laminins are found in call differentiated cells whereas B are in all nuclei

What are nuclear laminins responsible for?

Maintaining nuclear shape

What type of 3d structure do laminins form?

A 2D lattice like meshwork

What is laminin binding in the nucleus mediated by?

Lamin associated proteins (LAPs)