Lecture 04 - Cell-cell Communication

Question 1

When does cell organisation need to occur?

Answer 1

1. During development (embryogenesis)

2. During adult life (maintenance, homeostasis)

Question 2

How are cells organised?

Answer 2

1. Cells are organised through cell interaction and communication

Question 3

What does cell interaction and communication involve?

Answer 3

1. Cells interacting remotely (endocrine and paracrine)

2. Cells interacting directly (juxtacrine) in order to organise themselves into functional tissues

Question 4

What are the two functions of cell interactions?

Answer 4

1. Selective adhesions and stable attachments to maintain position
2. Signalling to regulate cell activity and behaviour

Question 5

Why are cell interactions important?

Answer 5

1. Crucial for organisation at the cellular level, during development and adult life

Question 6

How does signalling control cell behaviour through?

Answer 6

1. Survival (quiescence)
2. Growth and division (proliferation)
3. Specialisation (differentiation)
4. Death (apoptosis)
5. Movement (migration)

Question 7

How do selective adhesions work?

Answer 7

1. Involves the use of specific classes of proteins on the cell membrane
2. Allows for identification as to which cells to attach to
3. Interactions between proteins is non-junction so
4. Interaction is weak but selective

Question 8

How does cell attachment work?

Answer 8

1. Once identified, cell attachment can be stabilised by junctional contacts
2. These stabilise and join the cells together (adherence junctions and desmosomes)
3. It maintains tissue integrity by binding to the basal lamina (hemidesmosomes)
4. Gap junctions present to allow for the free movement of small molecules between adjacent cells
5. The attachment of the cells allows for the initiation of signalling pathways (which control proliferation and differentiation, as cadherins (desmosomes) can act as a receptor)

Question 9

What does selective cell interactions mean?

Answer 9

1. Selective cell interactions allows cells to sort themselves out and reform selective attachments due to the specific proteins
2. Attachments to cytoskeleton are also required in order to mechanically stabilise cells

Question 10

What are three applications?

Answer 10

1. Cell differentiation is accompanied by expression of cell-the specific surface proteins e.g. different types of cadherins present in a neural tube due to differentiation - shows the influence of the character of neighbours
2. Blood stem cell connections to the stromal cells via specific proteins - prevents differentiation and supports self-renewal, if the connection is lost, differentiation occurs
3. Notch signalling also blocks expression of genes required for differentiation, by the receptor (notch) binding to its ligand (delta) on adjacent cells. Therefore only one cell (at centre) is able to differentiate

Question 11

How do developmental abnormalities occur?

Answer 11

1. Problems during early developments arise as a result of failures in communication between cells
2. Malformations in heart result from defects in notch signalling
3. It can have a role in the development of cancer

Question 12

How does cancer develop?

Answer 12

1. The E-cadherin-b catenin complex plays a crucial role in epithelial cell-cell adhesion
2. Important for maintenance in tissue architecture
3. Perturbation in the expression or function of this complex leads to loss of intracellular adhesion
4. May lead to transformation of the cell and de-differentiation (failure to differentiate)
5. As a result, cell loses its identity
6. May lead to a loss in proliferative control
7. The loss of specific attachment can allow for metastasis
8. E-cadherin acts as a tumour suppressor protein, B cafe is part of a signalling pathway