Description of Cytoskeletal elements, Intermediate filaments, characteristics, EBS,ALS, cell Junctions

1. Intermediate Filaments
-Dr. Sarita Nanda
Biochemistry Department
Daulat Ram College

2. Introduction
 They have diameter between 8-11nm
 They provide mechanical strength to cells and tissues
 They provide scaffold for localization of cellular
processes

3. Intermediate Filament Proteins
 They are composed of variety of proteins
 There are 65 different intermediate filament
 Type I, II, III,IV, V and VI proteins
 Type I is acidic keratin which is of size 40-69 KD
found in epithelial cells
 Type II is neutral/basic keratin of 50-70KD found in
epithelial cells
 Type III is vimentin which is of 54 KD found in
fibroblasts

4. Intermediate Filament Proteins
 Type IV is neurofilament of 67-200 KD present in
neuron
 Type V is nuclear lamin which is of 60-79 KD which
is present in nuclear lamina
 Type VI is Nestin which is of 200KD which is present
in stem cells especially of CNS

5. Assembly of Intermediate Filament
 The first stage is it forms dimers.
 The dimers form tetramers The tetramers assemble
end to end to form protofilament
 The tetramers organize to form octamer
 They are arranged in antiparallel manner.
 Thus they are apolar. They do not have distinct ends
i.e. barbed or pointed end of intermediate filament.

6. Assembly of Intermediate Filaments

7. Intermediate Filaments

8. Characteristics
 Intermediate filaments are generally more stable than
actin filaments or microtubules
 They do not exhibit dynamic behavior associated with
other cytoskeleton
 Intermediate filament protein can be modified by
phosphorylation which can regulate their assembly and
disassembly.
 This is observed in nuclear lamin
 Cytoplasmic intermediate filaments such as vimentin are
also phosphorylated which lead to their disassembly and
reorganization in dividing or migrating cells

9. Intracellular Organization of Intermediate
Filament
 Both keratin and vimentin attach to nuclear envelop
serving to position and anchor nucleus within the
cell
 Intermediate filament associate with associate with
other cytoskeleton elements
 Intermediate filaments form junctions
 Desmosomes: cell-cell
 Hemidesmosome-cell-matrix

10. Junction Proteins
 On the cytoplasmic the junctions are associated with
plakins
 Plakins bind intermediate filaments
 Hemidesmosomes bind to different member od
plakins i.e. Plectins bind to other cytoskeleton
elements
 Desmin connects individual actin myosin assemblies
of muscle cell both one to another and to the plasma
membrane
 Neurofilaments are major intermediate filaments of
motor neurons , NF- L, NF-M, NF-H

11. Junction Proteins
 They help to support and stabilize other cytoskeleton
in thin extension of nerve cells

12. Junction Proteins
Hemidesmosomes

13. Diseases of Intermediate filament
 Epidermis bullous simplex(EBS)
 Mutant keratin gene form skin blister resulting from
cell lysis after minor trauma
 Lou Gehrig's disease (Amyotrophic lateral sclerosis,
ALS): leads to progressive loss of motor neurons
which lead to muscle atrophy, paralysis and eventual
death

14. Diseases of Intermediate Filaments

15. Diseases of Intermediate Filaments
Epidermolysis Bullosa Simplex (EBS)