Receptors & Cell Signaling Flashcards
What does a ligand-receptor complex do?
It will activate or inhibit cellular pathways.
What do effectors do?
They alter the activity of different components downstream. They generate secondary messengers that elicit a particular cellular response such as enzymatic activity, gene expression, etc.
What are some examples of effector proteins?
Metabolic enzymes
Gene regulatory proteins
Cytoskeletal proteins
What is endocrine signaling
Signal transported via blood
Long-distance
Long-lasting
Freely diffusing signal
*epinephrine
What is paracrine signaling
Signal diffuses to a neighboring target cell of a different cell type
Local signaling
Short-lived
*testosterone.
what type of signaling does testosterone do
Paracrine. Leydig cells synthesize and secrete testosterone which induces spermatogenesis by acting on Sertoli cells
What is autocrine signaling
Secreting cells also express surface receptors for the signal
Can release to cells of the same type
Common in chemokines
*Interleukins
What is direct/juxtacrine signaling
Signal binds to signaling cell which then binds to the receptor on a target cell.
Close contact is required.
*Heparin-binding epidermal growth factor binds to EGF receptor
Are water-soluble signals hydrophilic or hydrophobic
Hydrophilic
Are lipid-soluble signals hydrophilic or hydrophobic
HYdrophobic
Where do hydrophilic signals interact w/ receptors?
At the cell surface because they cannot penetrate the plasma membrane. Ex. epinephrine, insulin, glucagon.
which receptors are involved with hydrophilic signals?
G-protein coupled receptors (GPCRs)
Receptor tyrosine kinases (RTKs)
Where do hydrophobic signals interact w/ receptors?
Lipophilic signals pass through the plasma membrane of the target cell and bind to receptor proteins inside the cell
Ex. steroid hormones, thyroid hormones, retinoids
which transcription factors are involved with hydrophobic signals
Cytoplasmic receptors (inactive when attached to HSP90, activates upon ligand attachment, HSP90 dissociates, hormone-receptor translocates to nucleus to interact w/ hormone response element)
Nuclear receptors (already present in nucleus bound to DNA)
To become active, what must happen to the inactive G protein?
It must exchange its GDP for GTP. The active GTP-bound alpha subunit will separate from beta and gamma subunits.
What are the 4 different mechanisms to turn off a signal
- Decrease in hormone levels
- Remove the signaling molecule
- Receptor sequestration
- Receptor destruction
Rob4 and Rob11 both participate in receptor recycling and degradation. Which one is fast and which one is slow
Rob4: slow
Rob11: fast
How does viagra work?
Viagra inhibits cGMP PDE (cyclic gmp phosphodiesterase)
So, the cellular concentration of cGMP increases and effects are prolonged.
Prolonged effects: smooth muscle relaxation and vasodilation resulting in an erection.
“c (GMP) my boner?”
What does caffeine inhibit?
Caffeine inhibits PDE (phosphodiesterase usually breaks down cAMP) leading to accumulation of cAMP leading to increased HR
How does cholera toxin affect Gs-alpha
Cholera toxin prevents the INACTIVATION of G2-alpha, so it is always on (due to the ADP ribosylation of Arg in Gs alpha, leading to decreased GTPase activity). Adenylate cyclase is always stimulating, leading to overproduction of cAMP
How does too much cAMP affect intestinal cells
Too much cAMP opens Cl- channels, causing you to lose electrolytes and water leading to diarrhea.
How does the pertussis toxin affect cAMP levels
Pertussis prevents the ACTIVATION of Gi-alpha. ADP ribosylation of Cys on Gi-alpha prevents dissociation and activation of the alpha subunit. Leads to less inhibition og AC, thus more cAMP.
How does too much cAMP affect airway?
pertussis toxin causes loss of fluids and excessive mucous secretion- presents as whooping cough.
How does NO work to lower blood pressure and increase vasodilation?
NO activates guanylate cyclase, leading to production of cGMP resulting in smooth muscle relaxation.
How do antihistamines work
Antihistamines are lipophilic compounds that block the effects of histamine to the H1 GPCR
