Membrane receptors Flashcards
4 main types of receptor
ligand-gated ion channels
tyrosine kinase receptors
guanylate cyclase receptors
G protein-coupled receptors
Which receptors typically mediate fast responses?
Examples include nicotinic acetylcholine, GABA-A & GABA-C, glutamate receptors
Ligand-gated ion channel receptors
Two types of tyrosine Kinase receptor
- receptor tyrosine kinase
> insulin, insulin-like growth factor (IGF), epidermal growth factor (EGF) - non-receptor tyrosine kinase
> PIGG(L)ET: Prolactin, Immunomodulators (cytokines IL-2, Il-6, IFN), GH, G-CSF, Erythropoietin and Thromobopoietin
contain intrinsic enzyme activity
e.g. atrial natriuretic factor, brain natriuretic peptide
guanylate cyclase receptors
- mediate slow transmission and affect metabolic processes
- activated by variety of extracellular signals e.g. Peptide hormones, adrenaline, lipophilic hormones, light
- 7-helix membrane-spanning domains
- 3 main subunits: alpha, beta and gamma
G protein coupled receptor
G proteins are named according to the alpha subunit (Gs, Gi, Gq)
Describe the function of each
Gs - STIMULATES adenylyl cyclase
Gi - INHIBITS adenylyl cyclase
Gq - Activates phospholipase C
Mechanism of action of Gs receptor
Stimulates adenylate cyclase → increases cAMP → activates protein kinase A
Mechanism of action of Gi receptor
Inhibits adenylate cyclase → decreases cAMP → inhibits protein kinase A
Mechanism of action of Gq receptor
Activates phospholipase C → splits PIP2 to IP3 & DAG → activates protein kinase C
Give examples of Gs receptors
- Beta-1 receptors (epinephrine, norepinephrine, dobutamine)
- Beta-2 receptors (epinephrine, salbuterol)
- H2 receptors (histamine)
- D1 receptors (dopamine)
- V2 receptors (vasopressin)
- Receptors for ACTH, LH, FSH, glucagon, PTH, calcitonin, prostaglandins
Give examples of Gi receptors
- M2 receptors (acetylcholine)
- Alpha-2 receptors (epinephrine, norephinephrine)
- D2 receptors (dopamine)
- GABA-B receptor
Give examples of Gq receptors
- Alpha-1 receptors (epinephrine, norepinephrine)
- H1 receptors (histamine)
- V1 receptors (vasopressin)
- M1, M3 receptors (acetylcholine)