Cell receptors Flashcards
(14 cards)
What are cell receptors (5)
- Membrane-bound or intracellular
- Protein molecules that communicate signals
- Can be activated by molecules (known as ligands)
- Distribution and concentration vary in different tissues/organs.
- Therapeutic targets
How are receptors activated (2)
- Chemical interaction between receptor and ligand
- SPECIFICITY and SELECTIVITY of ligand-receptor interactions
What are the chemical interactions between receptor and ligand (4)
- Electrostatic interactions
- Hydrophobic interactions
- Stereospecific interactions
- Covalent bonds
What are the main types of receptors (5)
- G-protein coupled receptors
- Tyrosine kinase receptors
- Nuclear receptors
- Ligand-gated ion channels
- Voltage-gated ion channels
What are G-coupled receptors (5)
- Transmembrane and integral membrane proteins
- Receptor coupled with a G-protein
- Wide variety of different GPCRs - binding a range of ligands
- Ligands bind to extracellular domains, and signal transduction is activated intracellularly.
- Example: beta2-adrenoceptors
What are second messengers (3)
- Small molecules
- Formed in response to the activation of some receptors
- E.g. Cyclic nucleotides (cAMP) (via Adenylyl cyclase)
What are Tyrosine-Kinase receptors (8)
- Transmembrane proteins (two monomer units dimerise)
- Contain enzyme activity within receptor proteins – tyrosine kinases
- Monomers within the dimer cross-phosphorylate
- → signals intermediary signalling proteins that activate signalling pathways
- Example: Insulin receptor
- Activated receptor can accept phosphate groups from ATP to form ADP
- Intermediate proteins can obtain a phosphate group from the activated tyrosine-kinase receptor which in turn activates the intermediate receptor
- This triggers a ‘phosphorylation cascade’ resulting in a cellular response (via regulation of gene expression)
What are nuclear receptors (4)
- Intracellular receptors
- Agonists enter the cell – lipid soluble
- The ligand-receptor complex enters the nucleus and alters gene expression
- Example: steroid receptors
What are ion channel receptors (7)
- Ligand-gated AND Voltage-gated
- Receptor and effector (ion channel) are part of the same transmembrane protein
- Binding of agonist (for ligand-gated)/change of voltage across the cell (voltage-gated) results in the opening on the ion channel → membrane depolarisation
- Fast responding – in excitable cells
- Selective for which ions they allow to cross the membrane (Na+, Ca2+, K+, Cl-)
- Rely on there being a concentration gradient of the particular ion across the membrane.
- At rest there is ~ -70mV charge across the cell membrane
What are ligand-gated ion channels (3)
- The opening of the ion channel is dependant on the appropriate ligand binding
- Ligand binding can occur extracellularly (first messengers) or intracellularly (second messengers)
- Example: nicotinic Acetylcholine receptor (nAChR)
What are voltage-gated ion channels (4)
- The opening of the ion channel is dependant on the change in the cell membrane potential
- Size of depolarisation affects which voltage-gated channels open
- Go through a refractory phase **post re-closing
- Example: L-type Ca2+ channel
What is desensitation
Desensitisation is when the biological response of a receptor to its agonist diminishes when it is continuously or repeatedly exposed to the agonist
What is tachyphylaxis
Tachyphylaxis is used to describe desensitisation that occurs very rapidly
What is tolerance
Tolerance describes a more gradual loss of response of the receptor to its agonist
