Receptor Mediated Signals Flashcards
Basic steps in receptor signaling
Reception
Transduction- Amplification of signal
Response- change in gene expression
Primary Messenger
Like a hormone or ligand
Specific and can be mimicked by drugs
G-Protein Coupled Receptor
Transmemebrane protein loops around 7 times Largest family of proteins Examples of GPCR -Adrenergic (epi, norepinaphrine) Muscarinic (bind acetylcholine)
Types of G-Protein Receptor Ligands
Agonist - bind activate
Antagonist- Bind, no activation
GPCR Activation
G protein composed of 3 subunits (alpha, beta, gamma)
GDP is bound to alpha in inactive form
Ligand binds receptor and GDP is phosphorylated to GTP
Beta and gamma dissociate from alpha
Beta and gamma interact with effector enzymes to activate/inactivate(adenylate cyclase, phospholipase C)
Alpha will hydrolyze GTP to GDP and 3 subunits recombine
Adenylate Cyclase Second Messenger System
Primary messengercan increase or decrease adenylate cyclase activity
Adenylate cyclase is membrane bound enzyme converts ATP–>cAMP
cAMP–> activates certain kinases which phosphorylate enzymes
Epinephrine (Primary, binds adrenergic receptor A or B) can stimulate/inhibit production of cAMP
Phosphodiesterases break down cAMP–>AMP
Phospholipase C/Ca+ System
Phospholipase C is activated by neurotransmitters/hormones
Phospholipase C Cleaves PIP2–> IP3 and DAG
IP3 binds ER, causing intracellular influx of calcium
DAG activates Protein Kinase C –> activates enzymes
Receptor Tyrosine Kinase
Receptors and enzymes
4 main domains
Ligand results in dimerization of tyrosine containing inner receptor
Tyrosines are phosphorylated to become fully activated
Relay proteins bind and elicit response
Cytokine Receptors
Bind cytokines to control inflammation
Intracellular or Nuclear Receptors
Float around in the nucleus or cytosol
Bind hydrophobic molecules (steroid)
Ligand-receptor complex ofter works as a transcription factor
