Intermediate filaments are vital cellular components with diameters of 8-11 nm, providing mechanical strength and acting as scaffolds for various cellular processes. Composed of 65 distinct proteins, they include various types such as keratins, vimentin, neurofilaments, and others, which are structured in a stable and antiparallel arrangement. Dysfunction in intermediate filaments can lead to diseases like epidermolysis bullosa simplex and amyotrophic lateral sclerosis.

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)