Intermediate Filaments Flashcards
What is the size generally of Intermediate Filaments?
10 nm
TRUE OR FALSE:
Inermediate Filaments have HIGH tensile strength?
True
What are the SIX differences in Intermediate Filaments from microfilaments and microtubules?
- No bound nucleotides
- Not polar
- No motor proteins
- Less dynamic
- Subunits are more diverse
- Not found in plants / fungi
How many classes / families of Intermediate Filaments are there?
5
* all share 310 AA α-helical rod domain
* Non-helical head and tail domains differe between classes
How is the structure of an Intermediate Filament formed?
Rod domains dimerise through formation of a coiled-coil
What is the basic building block of Intermediate Filaments?
Dimers
How do two dimers combine in Intermediate Filaments?
Staggered anti-parallel fashion
TRUE OR FALSE:
Intermediate Filaments have polarity?
False
How are Intermediate Protofilaments formed?
Tetramers assemble end-to-end
What is formed when 4x Protofilaments are combined?
Protofibril
What is formed when 4x Protofibrils are combined?
Mature Intermediate Filament
What proteins are found in CLASSES I & II of Intermediate Filaments, where are they found and what is their function?
- Acidic Keratins - Class I
- Basic Keratins - Class II
- Function: Tissue strength and integrity
- Location: Epithelial cells
What proteins are found in CLASS III of Intermediate Filaments, where are they found and what is their function?
- Desmin, GFAP, Vimentin
- Location: Muscle, Glial, and Mesenchymal cells
- Function: Sarcomere organisation & integrity
What proteins are found in CLASS IV of Intermediate Filaments, where are they found and what is their function?
- Neurofilaments
- Location: Neurons
- Function: Axon organisation
What proteins are found in CLASS V of Intermediate Filaments, where are they found and what is their function?
- Lamins
- Location: Nucleus
- Function: Nuclear structure and organisation
How many different Acidic and Basic Keratin subunits form dimers?
50
Where are Hard Keratins found?
Hair and nails
What gives Hard Keratins their strength?
Disulphide bonds between abundant cysteines
Where are Soft Keratins found?
Epithelial cells
What is the function of Soft Keratins?
Strengthen and support cells
What TWO junctions do Soft Keratins associate with?
- Desmosomes
- Hemidesmosomes
What are Desmosomes?
Junctions between adjacent cells
What are Hemidesmosomes?
Junctions between cells and extracellular matrix
What disease is caused by mutations in Keratins?
Epidermolysis Bullosa Simplex
* skin disease characterised by blistering
What is the function of Lamins?
Strengthen and support the nuclear membrane
How many types of Lamins are there?
2
* Type A and Type B
What causes Lamin association with inner surface of the nuclear membrane?
Isoprenylation of Type B Lamins
What happens to Lamins during Mitosis?
Lamins are phosphorylated by a cyclin-dependent kinase
* key step in disassembly of the nuclear membrane
What diseases are caused by mutations in Type A Lamins?
- Emery-Dreifuss muscular dystrophy
- Hutchinson-Gilford progeria (premature ageing)
What gene is mutated in Hutchinson-Gilford progeria?
LMNA gene
How does the mutation of the gene in Hutchinson-Gilford progeria affect Type A Lamin?
Production of a truncated form that disrupts the nuclear lamina network
