on the other side of the plasma membrane of the cell & this allows those
adhesion complexes to adhere cells together into a larger tissue.
- Now he’s going to talk more specificity about adherens junctions.
- These epithelia are sheets of cells that line our body compartments so
it’s the most common architecture in our body, it lines all of our organs, it
forms our skin.
- Diagram: can see 2 epithelial cells – what you can think of here is these
individual cells are sort of like bricks in a wall, they add up together to
form this sheet of cells & this separates one body compartment from the
other. Here, for example, would be one body compartment, say the lumen
of the gut & on the other side of this would be the underlying tissue. The
adherens junctions are forming right b/w these cells – this cell is cutting
cross-section so this adherens junction is actually forming a ring right
around this cell & connecting that cell to all of its neighbours so you can
think of these adherens junctions as acting as mortar in b/w the bricks so
they’re found all around the cells, connecting all the cells together in the
Clustered cadherin adhesion receptors
- If we look close up at the molecular structure of these adherens
junctions we can see these 2 basic properties of a cell adhesion complex
as listed in the slide.
- Diagram: So we can see that right over here in this diagram so this is
one cadherin receptor in green so it has 5 blobs, a transmembrane domain
in the cytoplasmic tail so you can see this one cadherin forms a dimer
with another one which interacts with another dimer from the other cell &
another one & another one. This is just in 2 dimensions here but this will
form a 3D plaque of all of these receptors interacting with one another in
a cluster. Then these adhesion receptors then run through the plasma
membrane, on the other side they interact with adaptor proteins here in
blue & these adaptor proteins link the adhesion complex to actin
cytoskeleton shown by these red filaments in the diagram.
Five extracellular domains
A transmembrane domain
A cytoplasmic tail
- Here is the structure of the cadherin receptor in more detail, at the
- So for an adhesion molecule or adhesion receptor to mediate adhesion
b/w one cell & another, that receptor has to reach out from one cell &
make contact to another cell in the extracellular space. So these
molecules, they have to be a transmembrane proteins, they have to cross
the plasma membrane so they can reach out into the extracellular space &
contact other cells.
- Diagram: Here in the cadherin structure, there are 5 of these
extracellular domains so here again is one individual cadherin receptor,
this is a 2nd receptor so this is a dimer of the 2. So if we look in the
extracellular space here, we can see 5 of these repeats & each of these
repeats has a specific folded structure of the amino acid residues. So this
would be the N terminus of the protein, this folds into a specific structure
making up that domain & then the C terminus of this then connects to the
N terminus of the next one & this is all one continuous polypeptide all the