Chapter 16: Cell signalling
Made by Madelief van Berkel
Toelating Biomedische Wetenschappen 2023
I n this chapter, some of the important mechanisms by which cells send signals
and interpret received signals, are discussed:
- F irst→Overview of the general principles of cell
signalling
- Second→G-protein-coupled receptors
- Third→Enzyme-coupled receptors.
, 1.General principles of cell
signalling
ommunication frequently involves converting the signals that carry information
C
from one form to another. →signal transduction.Intypical communication
between cells, thesignalling cellproduces a typeofextracellular signal molecule
that is detected by thetarget cell. Most animalcells can both act as signalling
cells and target cells. Target cells have proteins called receptors that recognize
and respond to the signal molecule.
Signal transductionbegins when the receptor on atarget cell receives an
incoming extracellular signal and converts it to theintracellular signal molecules
that alter cell behaviour.
- Cell signalling→signal reception and transduction.
Signals can act over a long or short range.
here are many different types of extracellular signal molecules. Proteins,
T
peptides, amino acids, nucleotides, steroids, fatty acid derivatives, dissolved gases.
They all rely on basic styles of communication.
1) Endocrine signalling →Most public cell-to-cell
communication involves broadcasting the signal
throughout the whole body by secreting it into
the bloodstream (or the plants' sap). In this case,
the extracellular signal molecules arehormones.
endocrine cellsproduce hormones.
2) P
aracrine signalling →the signal molecules
diffuse locally through the extracellular fluid.
They remain close to the cell that secretes them. Thus, they act aslocal
mediatorson nearby cells. Signal molecules that regulateinflammation at
the site of an infection or that control
proliferation (multiplying) in a healing wound
do this. Sometimes cells can respond to their
own local mediators →autocrine signalling.
Cancer cells can promote their own survival
and proliferation like this.
, 3) N
euronal signalling. A message is not broadcast
widely butdelivered quickly and specifically through
private lines. The axon of a neuron terminates at
specialised junctions (synapses) on target cells that
can lie far from the neuronal cell body. A neuron
sends electrical impulses up to 100m/sec. On
reaching the axon terminal, these electrical signals
are converted into a chemical form. Each electrical
impulse stimulates the nerve terminal to release a
pulse of an extracellular signal molecule→
neurotransmitter.
4) C
ontact-dependent.This is the most intimate and short-rangeof all. It does
not require the release of a secreted molecule. Cells make direct physical
contact through signal molecules lodged in the plasma membrane of the
signalling cell and receptor proteins embedded in the
plasma membrane of the target cell.
uring embryonic development, this method allows
D
adjacent (aangrenzend) cells that are initially similar
to become specialised to form different cell types
→lateral inhibition.
any of the same types of signal molecules are used for these signalling
M
methods. The difference lies in the speed and sensitivity with which the signals
are delivered.
Made by Madelief van Berkel
Toelating Biomedische Wetenschappen 2023
I n this chapter, some of the important mechanisms by which cells send signals
and interpret received signals, are discussed:
- F irst→Overview of the general principles of cell
signalling
- Second→G-protein-coupled receptors
- Third→Enzyme-coupled receptors.
, 1.General principles of cell
signalling
ommunication frequently involves converting the signals that carry information
C
from one form to another. →signal transduction.Intypical communication
between cells, thesignalling cellproduces a typeofextracellular signal molecule
that is detected by thetarget cell. Most animalcells can both act as signalling
cells and target cells. Target cells have proteins called receptors that recognize
and respond to the signal molecule.
Signal transductionbegins when the receptor on atarget cell receives an
incoming extracellular signal and converts it to theintracellular signal molecules
that alter cell behaviour.
- Cell signalling→signal reception and transduction.
Signals can act over a long or short range.
here are many different types of extracellular signal molecules. Proteins,
T
peptides, amino acids, nucleotides, steroids, fatty acid derivatives, dissolved gases.
They all rely on basic styles of communication.
1) Endocrine signalling →Most public cell-to-cell
communication involves broadcasting the signal
throughout the whole body by secreting it into
the bloodstream (or the plants' sap). In this case,
the extracellular signal molecules arehormones.
endocrine cellsproduce hormones.
2) P
aracrine signalling →the signal molecules
diffuse locally through the extracellular fluid.
They remain close to the cell that secretes them. Thus, they act aslocal
mediatorson nearby cells. Signal molecules that regulateinflammation at
the site of an infection or that control
proliferation (multiplying) in a healing wound
do this. Sometimes cells can respond to their
own local mediators →autocrine signalling.
Cancer cells can promote their own survival
and proliferation like this.
, 3) N
euronal signalling. A message is not broadcast
widely butdelivered quickly and specifically through
private lines. The axon of a neuron terminates at
specialised junctions (synapses) on target cells that
can lie far from the neuronal cell body. A neuron
sends electrical impulses up to 100m/sec. On
reaching the axon terminal, these electrical signals
are converted into a chemical form. Each electrical
impulse stimulates the nerve terminal to release a
pulse of an extracellular signal molecule→
neurotransmitter.
4) C
ontact-dependent.This is the most intimate and short-rangeof all. It does
not require the release of a secreted molecule. Cells make direct physical
contact through signal molecules lodged in the plasma membrane of the
signalling cell and receptor proteins embedded in the
plasma membrane of the target cell.
uring embryonic development, this method allows
D
adjacent (aangrenzend) cells that are initially similar
to become specialised to form different cell types
→lateral inhibition.
any of the same types of signal molecules are used for these signalling
M
methods. The difference lies in the speed and sensitivity with which the signals
are delivered.
