Cell signalling Flashcards
What is cell signalling? (5)
Ability to communicate between cells Need to respond to the environment Quorum sensing Respond to signals from other cells Co-ordinate growth and development
What are the 4 forms of intracellular signalling?
Contact dependent - membrane bound signalling molecule
Paracrine - signals released into extracellular space, act on neighbours
Synaptic - neurotransmitter
Endocrine - hormones released
What is a ligand/agonist?
Binds to receptor and activates it
What is an antagonist?
Binds to receptor and does not activate it
What is a first messenger?
Ligand/agonist/hormone
What is a second messenger?
Intracellular molecule produced in response to first messenger (Cyclic AMP)
What is a signal transduction?
Process by which signal is transmitted into cell and then produce a final response
Describe a simple signalling pathway: (4)
- Signal molecule binds to receptor protein
- Receptor activates 2nd messenger, signals a cascade
- Signalling cascade influence traget protein
- Signal transduction - alters gene expression
How can you amplify a signal? (7)
Hormone –> receptor –> G-protein –> Effector –> 2nd messenger –> kinase –> phosphorylated enzyme
What is cross talk?
Different signal transduction pathways may converge on a common target (enhance or attenuate response)
What are the 2 types of first messengers?
Ligands: Hydrophobic ligands (steroid hormones) permeable Hydrophilic ligands (proteins) impermeable
What are the 2 types of receptors?
Intracellular receptors
Cell-surface receptors
What can cell surface receptors be bonded to for? (3)
Ion channels
G-protein coupled receptors
Enzyme coupled receptors
How does an ion-channel coupled receptor work? (3)
Ligand binds to extracellular receptor
Channel opens to allow flow of ions
Change in cytoplasmic ion conc elicits cells response
How do G protein coupled receptors work? (3)
Ligand binds to G protein
Activates intracellular G protein
Actives enzyme, changes conc of 2nd messenger
How does an enzyme coupled receptor work? (3)
Ligand binds to cell surface receptor
Activation of enzyme activity of receptor
Recruitment and activation of intracellular enzyme
What does a nuclear receptor do? (5)
Bind to ligand in the cytoplasm or nucleus Loose an inhibitory protein Bind to a co-activator protein Bind to specific DNA region Activates gene transcription
How does the nuclear receptor work?
- Inactive form receptor is bound to inhibitory protein complex
- Ligand binding causes dislocation of inhibitory complex - stimulates gene transcription
- Binding of ligand causes a conformational change in the receptor - allows coactivators to bind
What is tamoxifen role on oestrogen?
Tamoxifen binds to estrogen receptor and blocks binding to coactivators
