(L16) Receptors and Cell Signaling Flashcards
What is endocrine signaling?
What are examples?
L16 S8
Signal is:
- transported via blood stream
- long distance
- long-lived
Examples:
-epinephrine
What is paracrine signaling?
What are examples?
L16 S9
Signal is:
- local, diffuses to nearby cells
- short-lived
Examples:
-testosterone
What is autocrine signaling?
What are examples?
L16 S10
Signal is:
-directed secreting cell and neighboring cells of the same type
Examples:
- chemokines
- growth factors in tumors
What is juxtacrine signaling?
What are examples?
L16 S11
Signal is:
-attached to signaling cell and requires direct contact between signaling cell and target cell
Examples:
-immune cells
What are the characteristics of hydrophilic signals?
L16 S15
Unable to cross cell membrane
Receptors on are surface of target cells (GPCR, RTK)
Use second messengers inside the cell
Short-lived
What are the characteristics of lipophilic signals?
L16 S16
Able to cross cell membrane
Receptors inside of target cells (cytoplasmic or nuclear)
Signal-receptor complex acts as transcription factor that acts on DNA or associated proteins
Long-lived
Mostly categorized as hormones
What is the general structure of a GPCR?
L16 S19
Extracellular domain (ECD): -binds signal
Transmembrane domain (TM): -7 α helicies
Intracellular domain (ICD): -interacts with G protein
What is the general GPCR signaling pathway.
- ECD of GPCR binds ligand causing conformation change
- ICD of GPCR exchanges GDP for GTP on G protein, activating it
- G protein interacts with membrane bound effector protein generating second messengers
- second messengers interact with target creating biological response
What is the structure of a G protein?
What happens to each portion after being activated?
L16 S24
Subunits:
- α
- β
- γ
α subunit has GDP exchanged for GTP upon activation. It also breaks away from the β and γ subunits to interact with effector protein
How can signals be desensitized?
L16 S25
- drop in hormone levels
- remove secondary signaling molecule
- sequester receptor (forms endosomes that later refuses with cell membrane)
- destroy receptor (forms endosomes that fuses with lysosome)
What are the different secondary effector methods of GPCR signaling?
L16 S28
Gs:
- ligand activates
- activates adenylate cyclase producing cAMP
- cAMP activated PKA
- cAMP removed by phosphodiesterase
Gi:
- ligand activates
- inhibits adenylayte cyclase
- cAMP is not produced and PKA is not activated
Gt:
- light activates
- activates cGMP phosphodiesterase removing cGMP
Gq:
- ligand activates
- activates PLC cleaving PIP into IP3 (activates Ca+ signaling) and DAG (activates PKC)
What is the effect of hydrolyzing cyclic nucleotides and what happens when this process is inhibited?
L16 S30
Panini pg. 100
Cyclic nucleotides act as secondary messengers so hydrolyzing them stops their downstream biological activity.
When hydrolysis is inhibited, the secondary messenger increase in concentration and increase the downstream biological effect.
What is the effect of cholera toxin?
L16 S31
Panini pg. 100
Overly activates Gsα by decreasing its GTPase activity preventing it from being inactivated.
Stimulates adenylate cyclase
What is the effect of pretussis toxin?
L16 S33
Inhibits Giα preventing inhibition of adenylate cyclase
What is the effect of NO?
L16 S34
Activates guanylate cyclase producing cGMP in smooth muscle causing relaxation and vasodilation
