CELL SIGNALLING 1
A chemical signal released by one cell is recognised by another cell
Usually involves a receptor molecule that recognises the signal in a highly specific manner
Allows the recipient cell to make a characteristic response
Why is cell signalling important?
Essential for co-ordination of cell behaviour
Single cell organisms, such as yeast, use signalling to identify and interact with cells of the correct mating type in sexual reproduction
Multicellular organisms depend on cell signalling for correct development, tissue maintenance and homeostasis
Important in development
Some of the cellular “decisions” made during development of a multicelluar organism
that are influenced by cell signalling. Mis-regulation of these processes can lead to
Importance in tissue homeostasis
After a meal the rise in blood glucose and amino acids triggers release of the hormone
Insulin from the pancreatic beta-cells. Insulin acts on key tissues to promote storage of
energy reserves. Failure of the pancreatic beta-cells (insufficient insulin production) or
failure of the peripheral tissues to respond to insulin (insulin insensitivity) results in
Types of cell signalling
Lateral inhibition mediated by the delta-notch signalling system
During development in parts of the nervous system two specialized cell types (neurons and support cells) are formed in an organised manner through contact mediated cell signaling involving Delta (signal) and Notch (receptor).
The unspecified epithelial cells are essentially equivalent, with each cell signaling to its neighbours to maintain low levels of neurogenin (in turn promoting low levels of Delta expression)
Some cells will express, by chance, slightly higher levels of Delta. This signals to surrounding cells to prevent neurogenin expression and; i) stops them from differentiating as neurons; ii) reduces their...