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Which of the following is a feature shared by intermediate filaments and microtubules?
A. They both have polarity
B. They are all self polymerizing
C. They are used for trafficking by motors
D. They are all cytoplasmic

B. They are all self polymerizing.


Intermediate filaments are located where?

1. Nucleus (Laminin)
2. Cytoplasm


What is GFAP?

Glial fibrillary acidic protein


What is the progenitor cell?

(Stem cell) May still differentiate, but is already more specialized than a stem cell.


Which of the following features are true for all classes of intermediate filaments?
A. They are composed of mostly globular proteins.
B. They contain a nucleotide binding site.
C. They are composed of mostly alpha-helical coiled-coil domains.
D. They are all cytoplasmic
E. B,C, and D are correct

C. They are composed of mostly alpha-helical coiled-coil domains.


What is IF-Assembly?

An experiment finding that separate assembly of different intermediate filaments could come together and assemble together.
- Not done in Actins and MTs
- Could be due to the lack of polar ends


What are desmosomes?

Anchoring junctions
1. Rivets through the plasma membrane of adjacent cells.
2. IFs composed of keratin are attached to membrane-associated attachment proteins that form a dense plaque on the cytoplasmic face of the membrane.
3. Cadherin molecules form the actual anchor by attaching to the cytoplasmic plaque, extending through the membrane and binding strongly to cadherins coming through the membrane of the adjacent cell.


What are adherens Junctions?

Anchoring Junction
1. Share the characteristic of anchoring cells through their cytoplasmic actin filaments.
2. Similar to desmosomes and hemidesmosomes, their transmembrane anchors are composed of cadherins in those that anchor to other cells and integrins in those that anchor to extracellular matrix.


What feature is true for all classes of IFs?

They are composed of mostly alpha-helical coiled-cell domains.


A unit length of IF is what?

~60 nm


Keratins are a major component of what?

Hair, nails, skin


Keratin connects to what?

Desmosomes and hemidesmosomes


Hydrolysed keratin has become a common cosmetic ingredient due to its _______.

Moisturizing properties


Beta-keratin is common in birds and reptile scales, but is formed by ________ instead of ______.

Formed by stacks of Beta-sheets instead of alpha-helical coiled cells.


Type I keratins are what #s and pH?

Acidic, Keratins 1-8


Type II Keratins are what #s and pH?

Basic, Keratins 9-20


The cross linkage of IFs to MTs, MFs, and other IFs is mediated by what?

Elongated dimeric proteins called Plectins (Plakin-family member)


What is Keratinopathies?

Mutations on Keratins


What keratin mutation causes epidermolysis bullosa simplex?

Keratin-5 (weber cockayne syndrome) or -14 (down-meara form) => skin lesions


What keratin mutation causes ichtyosis bullosa of slemens?

Keratin-2e => dry, flaky skin, babies may show blisters


What keratin mutation causes epidermolythic hyperkeratosis?

Keratin-1 or -10, clumping of IFs => skin


What keratin mutation causes steatocystoma multiplex?

Keratin-17 => multiple cyst formation


What keratin mutation cuases Kerathosis pharngis?

Keratin ?? grow on the surface of the pharynx, tonsils and lingual tonsils.


What is desmin and where?

1. Located at the Z-line in sarcomere of cardiac and skeletal muscle, but also found in smooth muscle.
2. Gradually replaces vimentin after embryogenesis and higher differentiation of muscle cells.
3. Only found in vertebrates, but with homologous proteins in other metazoan cells.
4. Also links mitochondria to sarcomere.


What is DRM aka Desminopathy?

Desmin-related Myofibrillar Myopathy: occurs with mutations in the gene that codes for desmin. Prevents proper filament assembly, instead forms aggregates of desmin and other proteins throughout the cell.


Lack of desmin filaments does what to the heart muscle?

Weakens it.


What are lamins?

Type-V IFs that form a basket underlying the nuclear membrane (NM) giving it strength and organization.


Nuclear lamina are linked to the NM by what?



Where are lamins reversibly phosphorylated and what is the result?

At their head and tail domains during mitosis, causes disassembly of the nuclear lamina.


Where are Lamin A and B found?

Metazoan cells


Where are Lamin A/C and B found?



What is the product of the LMNA gene and its function?

Lamin A/C is the product and is a major component of the nuclear lamina.
- Lamina A and C are different splicing products.
- Other lamins in vertebrates are lamina B-type


What is MPF?

Mitosis promoting factor (MPF): during Mitosis, the nuclear lamina is disassembled through phosphorylation by MPF.


What is Laminopathies?

A group of rare genetic disorders caused by mutations in genes encoding proteins of the nuclear lamina => nuclear envelopathies.


What is EDMD?

Emery Dreifuss Muscular Dystrophy: affects muscles involved in movement such as skeletal and cardiac muscle.


What is Emerin?

A transmembrane protein of the inner nuclear membrane that interacts with lamins (lamina-binding). It is essential for the function of skeletal and cardiac muscle, but the exact molecular mechanism of EDMD is not clear.


How many types of EDMD are there?

6 types with very similar symptoms.


What is x-linked EDMD?

Mutations on the Emerin gene. X-linked EDMD is the most common form of EDMD and affects about 1 in 100,000 people. (Skeletal/Cardiac: Emerin)


What is autosomal dominant = EDMD2?

Mutations on the LMNA gene that produces both of the closely related Lamin A and C proteins. (Skeletal/cardiac: Lamin A/C)


What is autosomal recessive = EDMD3?

Sames as for the dominant version, much less common. (Skeletal/cardiac: Lamin A/C)


What is HGPS?

Hutchinson-Gilford Progeria Syndrome: Progeria is a rare, fatal genetic condition characterized by an appearance of accelerated aging in children. (Progeria is not caused by defective DNA repair like other age accelerating diseases are)
- a Laminopathy


How does HGPS occur (genetics)?

Lamin A with a silent point mutation on its DNA sequence disrupts correct Pre-mRNA splicing of prelamin and causes a 50 residue deletion that in turn prevents cleavage of the C-terminus farnesylated Fragment resulting in Progeria. (1 in 8 million people affected)


What is CMT?

Charcot-Marie-Tooth disease: an inherited demyelinating disease of the peripheral nervous system. (Neurofilament light chain: NF-L)


Type IV IFs have 3 chains that are:

NF-L (light): 68-78kDa
NF-M (medium): 145-160kDa
NF-H (heavy): 200-220kDa


What are the different diseases considered Laminopathies?

1. Emery Dreifuss Muscular dystrophy
2. Cardiomyopathy (dilated heart)
3. Charcot Marie-Tooth disease
4. Greenberg dysplasia
5. Hutchinson-Gilford Progeria syndrome