Receptors and Cell Signaling Flashcards
Describe endocrine signaling and give an example.
Signal (hormone) is transported via blood. Long-distance and long-lasting.
Example: epinephrine
Describe paracrine signaling and give an example.
Signal diffuses to neighboring target cell of a different cell type. Local and short-lived.
Example: testosterone
Describe autocrine signaling and give an example.
Secreting cells express surface receptors for the signal, affecting cells of the same type.
Example: interleukin-1 produced by T-lymphocytes during immune response to promote own replication.
Describe direct/juxtacrine signaling and give an example.
Signal binds to signaling cell which then binds to receptor on the target cell.
Example: heparin-binding epidermal growth factor
Give examples of hydrophilic signals and receptors.
Signals: epinephrine, insulin and glucagon
Receptors: G Protein Coupled Receptors (GPCRs) for glucagon and Receptor Tyrosine Kinases (RTKs) for insulin
Give examples of lipophilic signals and receptors.
Signals: steroid hormones, thyroid hormones and retinoids
Receptors: Cytoplasmic receptors, binds hormone, translocates to nucleus, binds to hormone response element (HRE) on DNA. Nuclear receptors, hormone binds to receptor already on DNA.
What are the structural motifs of a G Protein-coupled Receptor (GPCR)?
- Extra Cellular Domain (ECD)
- Trans Membrane Domain (TM)
- Intracellular Domain (ICD)
Describe the general steps of GPCR signaling.
- Ligand binds, causing conformational change in the GPCR.
- ICD activates its G protein by triggering exchange of GDP to GTP.
- Activated G protein interacts with membrane bound effector protein, leading to signal cascade.
- Inactivated by GTPase activity of G protein. Can be accelerated by GAP.
What part of the trimeric G protein dissociates from the rest and activates/inhibits effector molecules?
The alpha subunit when GTP is bound.
What is the difference between GPCR signaling via Gs and Gi?
Gs stimulates adenylate cyclase, Gi inhibits. Adenylate cyclase produces cAMP, which leads to the phosphorylation of targets.
Describe GPCR signaling via Gt.
Light stimulates GPCR, leading to the activation of cGMP phosphodiesterase.
Describe GPCR signaling via Gq.
Leads to activation of phospholipase C. Further leads to phosphorylation of targets AND release of Ca2+ from RER.
What are the ligands for Gs and Gi?
Gs: Epinephrine and Histamine
Gi: Epinephrine/norepinephrine and Dopamine
What is the ligand for Gq?
Acetylcholine
How does viagra work?
Inhibits cyclic-GMP Phosphodiesterase, leading to an increased concentration of cellular cGMP. Leads to smooth muscle relaxation, vasodilation, and an erection.
