Hormone Signaing Pathways Flashcards
Endocrine signaling
H released into bloodstream to travel a long distance to reach its target.
Paracrine signaling
H released to act on a neighboring cell.
Autocrine signaling
H acts on the same cell that secreted it.
Juxtacrine signaling
H stays attached to secreting cell and binds to a receptor on an adjacent target cell.
How do hydrophilic Hs signal?
Bind to receptor on CM and induce a second messenger system.
What receptors can hydrophilic Hs use?
GPCRs
RTKs
Lipophilic Hs signal how?
They cross the CM to act as a transcription factor.
What receptors do lipophilic Hs bind?
Cytoplasmic receptors
Nuclear receptors
What is the hormone response element (HRE)?
The DNA sequence that the hormone-receptor complex (from the cytoplasm) binds to in the nucleus.
What are nuclear receptors bound to?
DNA directly
What kind of half-lives do hydrophilic meds have?
Very short (sec to min). Given at time of need (ex: Epi).
What kind of half-life do lipophilic meds have?
Long half-life (hours to days). Can be taken daily (birth control).
Hoe does an inactive G protein become active? Which enzyme facilitates this?
It must exchange its GDP for GTP. GEF causes this transaction.
How does the active GTP become inactivated?
There is intrinsic GTPase activity that hydrolysis GTP back into GDP.
What is the function of GTPase-activating protein (GAP)?
It accelerates the activity of GTPase, causing an increase in the rate of hydrolysis of GTP to GDP.
What occurs with the alpha, beta and gamma subunits once GTP is active?
Beta and gamma subunits remain intact and dissociate, leaving alpha attached to GTP.
How does the Gs pathway function?
What stops the cascade?
GTP activates AC —> cAMP —> active PKA —> phosphorylates target.
CAMP is acted on by PDE.
How does the Gi pathway work?
GTP inhibits AC and cAMP is not produced.
How does Gt pathway work?
Light causes GTP to act on cGMP PDE to convert cGMP to 5’-GMP.
How does Gq pathway work?
GTP binds PLC which increases intracellular Ca levels.