BIOL10002 Lecture Notes - Lecture 11: Protein Kinase A, Extracellular Fluid, Neuromuscular Junction
Lecture 11
Cell to Cell Communication
Signalling
- Many biological processes require signals.
- Signals can be heat, light, sound or molecules. Receptors are often proteins.
- Cells will only respond to a signal if they have a specific receptor for it.
- receptor binding usually causes the receptor to change shape which triggers a cellular response.
1. A signalling molecule or ligand binds to a receptor
2. Transduction (conveying message to cell)
3. Response (effects)
Signalling molecules or ligands that act at a distance are called hormone action.
- through blood or interstitial fluid
Molecules that act on the cell that released them are called autocrine.
Molecules that act on nearby cells are called paracrine.
- these are local; only travel through interstitial fluid.
Nuclear receptors always activate or inhibit RNA transcription.
Cytoplasmic receptors may affect RNA – intracellular receptors attached to a chaperone
which inhibits receptor until it receives a signal, which changes the shape of the receptor,
triggering the release of the chaperone.
Membrane receptors affect nucleus by cellular response, or create their own cellular
response.
Membrane-bound receptors
1. Ligand-gated ion channel receptors
direct transduction
found in nervous system or neuro-muscular junction
Neurotransmitter binds to receptor, which changes shape (e.g. acetylcholine)
shape change allows ions to travel through receptor into the cell
2. G-protein linked receptors (guanine) – only found in eukaryotes
signalling molecule binds to receptor
shape change triggers an exchange of GDP for GTP
G-protein is thus activated, which activates effector protein
after activating effector, GTP is hydrolysed to GDP (i.e. energy is used, so G-protein is now inactivated)
This is an AMPIFYING reaction. Active 20, which activates 100, which activates 1000 etc
PKA (Protein Kinase A) inhibits glycogen synthetase – preventing glucose conversion to glycogen
3. A Protein Kinase Receptor
Indirect transduction via second messenger
α subunits bind to signalling molecule
dimerization of receptors (’go together’) – receptors phosphorylate each other
PK phosphorylates Insulin-response substrate, leading to cellular response
* an insulin response can lead to activate other proteins such as Ras
Ras Proteins – small GTPases (family of proteins)
Ras stimulates cell proliferation when activated with GTP, and is then switched off in a normal cell
In cancer cells, Ras is not switched off and cells proliferate uncontrollably, forming tumours
find more resources at oneclass.com
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Document Summary
Signals can be heat, light, sound or molecules. Cells will only respond to a signal if they have a specific receptor for it. Receptor binding usually causes the receptor to change shape which triggers a cellular response: a signalling molecule or ligand binds to a receptor, transduction (conveying message to cell, response (effects) Signalling molecules or ligands that act at a distance are called hormone action. Molecules that act on the cell that released them are called autocrine. Molecules that act on nearby cells are called paracrine. These are local; only travel through interstitial fluid. Nuclear receptors always activate or inhibit rna transcription. Cytoplasmic receptors may affect rna intracellular receptors attached to a chaperone which inhibits receptor until it receives a signal, which changes the shape of the receptor, triggering the release of the chaperone. Membrane receptors affect nucleus by cellular response, or create their own cellular response. Found in nervous system or neuro-muscular junction.
