Cadherins & Catenins, Developmental biology.

1. THE GLUE THAT HOLDS LIFE
TOGETHER

2. Cadherins – Calcium dependent adhesion mol.
Def. – Cadherins are calcium-dependent cell
adhesion molecules that bind to other cadherins of
the same type (homophilic)

3. Proteins involved in cell-cell adhesion (sticking)
They unite epithelial cells to form sheets &
mesenchymal cells to form aggregates
They separate different tissues from one another
(sorting)

4. Polypeptides: 720-750 a.a.
Components/Domains:
1. Cytoplasmic/Intracellular
2. Transmembrane
3. Extracellular

5. Calcium independent:
• Immunoglobulin superfamily (IgSF) CAMs
• Lymphocyte homing receptors/addressins
Calcium dependent:
• Integrins
• Selectins
• Cadherins

6. It is a framework of polymeric protein filaments inside the
cells
Provides stability to the cell
Generates forces leading to changes in cell shape and cell
movement
Facilitates intracellular transport of organelles
Communicates with extracellular matrix

7. Microfilaments (Actin)
Microtubules
Intermediate filaments (keratin)

8. Polarized actin polymers found in cytoplasm of eukaryotes
Arranged in bundles & lattices
Provide strength & support
Associates with myosin fibers to generate contractile fibers
• Which facilitate change in cell shape & movement
• Forms contractile ring during cytokinesis

9. Polarized structure comprising a circular arrangement of
polymerized tubulin protofilaments found in cytoplasm
Maintenance of axons, microvilli, cilia, etc.
Mitotic spindle apparatus
With the help of motor proteins (kinesis and dynein) they
facilitate intracellular transport.

10. Fulfil a structural role
Ex: neurofilaments, keratin, etc.
Polymers of 10nm. in diameter
Possess a conserved α-helical structure
It has a N-terminal & C-terminal

11. Interactions:
1. Cell-cell
2. Cell-extracellular matrix
Bindings:
1. Heterophilic
2. Homophilic

12. Functions:
1. Establishing & maintaining intercellular
connections
2. Spatial segregation of cells
3. Organization of animal form

13. There are over 100 cadherins in vertebrates
And fewer than 20 in invertebrates
Four groups of cahderins:
1. Classical
2. Desmosomal
3. Protocahderins
4. Unconventional

14. 1. E-cadherins (epithelial cadherin or uvomorulin or
L-CAM)
2. P-cadherins (placental cadherin)
3. N-cadherin (neural cadherin)
4. EP-cadherin/C-cadherin (frog blastula)

15. ‘Catenin’ => Latin for chain
Def. – family of proteins found in complex with cadherins
of animal cells
Types:
1. α-catenin
2. β-catenin
3. γ-catenin
4. 𝛿-catenin

16. Functions as a linking protein between cadherins & actin
containing filaments of the cytoskeleton
It has been reported that it can also bind with vinculin &
α-actinin
Regulates actin filament assembly
Doesn’t have armadillo repeats

17.  Dual function protein: Regulates coordination of cell-cell adhesion
and gene transcription
 Alterations in localizations & expression levels => cardiac diseases
 Mutation & overexpression => cancer
 In humans – CTNNB1 gene
 Homologous to γ-catenin

18. Contains 10 armadillo repeats
 𝛿-2-catenin is expressed in brain
Types:
1. 𝛿-1-catenin
2. 𝛿-2-catenin

19. Humans: JUP gene
Homologous to β-catenin
Cytoplasmic component of desmosome and
adherens junction in cardiac muscles

20. Sticky junction where the transmembrane protein fibers
adhere to each other in the extracellular matrix