Signal Transduction

Question 1

List the major types of cellular receptors, describe their general properties and explain their signal transduction pathways

Ligand-gated ion channel receptors:

Answer 1

Ionotropic, receptor/channel
Transduce chemical signals to electrical signals – signaling between electrically excitable cells (like neurons)

Question 2

G protein-coupled receptors (largest family)

Answer 2

G proteins: Heterotrimers, a subunit hydrolyzes GTP
GTP-binding proteins (Ras) regulate G proteins

Steps: 1.) Ligand binds, receptor activates
2.) G protein interact with receptor. conformational change, GDP exchanged for GTP.
3.) G protein dissociates from receptor
4.) a-GTP and BY subunits dissociate
5.) Both a-GTP and BY now interact with effectors
6.) a-catalyzed hydrolysis of GTP to GDP inactivates a and promotes reassembly of trimer

Question 3

Catalytic receptors

Answer 3

Receptor Guanylyl Cyclase (GTP-> cGMP)
Natriuretic peptides like ANP bind to these receptors
Relaxes vascular smooth muscle (blood vessel dilation) and enhances Na+ excretion in urine

Soluble Guanylyl cyclase: binds NO

Receptor Tyrosine Kinases: Phosphorylate themselves in addition to other cellular proteins

Question 4

Nuclear receptors

Answer 4

steroid/thyroid hormones - bind to intracellular (cytoplasm or nuclear) receptors
Act as ligand-activated transcription factors
hormone enters cell membrane, enters nuclear DNA via pores