Receptor Diversity Flashcards
What is a receptor?
A molecule (usually a protein) inside, or on the surface of, a cell that binds to a specific substance (ligand) and causes a consistent physiological effect in the cell.
Define “agonist”
Mimics the action of an endogenous ligand
Define “antagonist”
Blocks the action of an endogenous ligand
Define “Allosteric modulator”
Binds to a site distant from the ligand binging site (aka orthosteric site) to exert its effect
How can a ligand interact with a receptor? Give the types of ligand
Ligands can behave as;
- Agonists
- Antagonists
- Allosteric Modulators
Give some types of receptors
Ligand-gated ion channels
Kinase-linked receptors
GPCRs
Nuclear receptors
Describe ligand gated ion channels
Ions interact with the receptor to cause hyperpolarisation or depolatisation, which then has other effects within the cell. Eg nicotinic acetylcholine receptor
Describe how kinase-linked receptors exert their effects
Pathway: ligand binding, receptor autophosphorylation, protein phosphorylation, gene transcription, protein synthesis, cellular effects.
Describe receptor tyrosine kinases
Single transmembrane domain polypeptides which dimerise upon ligand binding. C termini of each monomer phosphorylate the other, autophosphorylation, on specific residuesto form phosphotyrosine docking sites for proteins. This creates a scaffold for intracellular signalling pathways. Eg EGFR, insulin
Describe GPCRs
Ligand interacts with a receptor, causing the G protein to split into its constituent subunits, which will go on to exert their effects.
Large family, basic common structure; single polypeptide chain 300-1200 AAs. extracellular N terminus, intracellular C terminus. Seven transmembrane domains. Eg muscarinic receptors
Describe nuclear receptors
Found on or within the nucleus of the cell. Ligands must be lipid soluble to pass through membranes. Exert effects through altering transcription, via transcription factors, histone acetylation, DNA methylation etc.
Define a partial agonist
A ligand which will bind to a receptor but will never elicit a full response as compared to the endogenous ligand. Exhibits reduced efficacy.
Define an inverse agonist
Binding of the ligand has the opposite effect to an agonist. An antagonist causes nothing to happen, aka a neutral agonist, whereas an inverse agonist makes the agonist outcome less likely.
Define a biased agonist
A ligand which, when binding to a receptor, will be more likely to induce signalling along a certain secondary pathway than another. Eg PLC over Akt, etc.
