Cell Adhesion Molecules

Presentation: Cell Adhesion Molecules

1. CELL ADHESION MOLECULES
Syed Muhammad Khan (BS Hons. Zoology)

2. Introduction
Cell adhesion molecules are present in plasma
membrane.
They help similar cells to adhere together.
They help in creating boundaries between different
tissues.

3. Introduction
Cells have differential affinity for other cells.
Cell adhesion molecules help cells in acting upon this
differential affinity.
Cells adhere to each other and arrange themselves
in the most stable (thermodynamically) form.

4. Introduction
The most important type of cell adhesion molecules
are the cadherins.
Other cell adhesion molecules include:
1.Integrins
2.IgCAMs(Immunoglobulin superfamily members)
3.Selectins

5. Cadherins
Cadherinsare calcium-dependent adhesion
molecules.
Cadherinsare trans-membrane proteins
They interact with other cadherinson adjacent cells.
The cadherinsare anchored inside the cell by a
complex of proteins called catenins.

6. Cadherins
Cadherin proteins perform several related functions:
1.Their external domains serve to adhere cells together.
2.Cadherinslink to and help assemble the actin
cytoskeleton.
3.Cadherinscan serve as signaling molecules that
change a cell's gene expression.

7. Cadherin-based Cell adhesion Junctions

8. Cadherins(Types)
Several types of cadherinsexist, some of them are:
1.E-cadherins(Embryonic cells & Epithelial cells)
2.P-cadherins(Placenta)
3.N-cadherins(Neural cells)
4.R-cadherins(Retina)

9. Protocadherins
Protocadherinslack the attachment to the actin
skeleton through catenins.
Expressing similar protocadherinsallows keeping
migrating epithelial cells together.
Expressing dissimilar protocadherinsallows
separating tissues.

10. Cadherins
The action of cadherinsis affected in two ways:
1.Quantitative (Ammount)
2.Qualitative (Type) -Expression of N-cadherin
separates the precursors of the neural cells from
the precursors of the epidermal cells.

11. Cadherins–With Other Systems
During development, the many cadherinsoften work
with other adhesion systems.
After fertilization, the embryo must adhere to and
embed itself in the uterine wall.
Here, the trophoblastcells (the outer cells that bind
to the uterus) are differentiated from the inner cell
mass (those cells that will generate the embryo and
eventually the mature organism).

12. Cadherins–With Other Systems
Trophoblastcells have several adhesion
molecules that anchor the embryo to the uterine wall:
E-and P-cadherins(these two molecule types
recognize similar cadherinson the uterine cells).
Integrin proteins(receptors) for the collagen and the
heparansulfate glycoproteins of the uterine wall.
Modified glycosyltransferaseenzyme that
extends out from the cell membrane and can bind to
specific carbohydrate residues on uterine glycoproteins.

13. Other Adhesion Molecules
Calcium Independent:
1.Integrinsaretransmembranereceptors that facilitate
cell -extracellular matrix(ECM) adhesion.
2.IgCAMsare immunoglobinsand adhesion molcules, i.e.
VCAM and NCAM.
Calcium Dependent:
Selectinsare single-chain trans-membrane
glycoproteins.