Mechanism of Hormone Action & Second Messengers Flashcards
What is the final outcome interaction of hormone and target cells? It depends on several factors…
hormone concentration
receptor number
affinity of hormone for receptor
duration of exposure to hormone
intracellular factors
What is the threshold response?
minimal concentration of hormone needed to elicit a measurable response
- dose-response curve
What is this curve called?
dose-response curve
Responsiveness is expressed in a _______ relationship
dose-response
The magnitude of the response correlated with _________
hormone concentration
As hormone concentration increases, response [increases/decreases] then levels off
increases
More receptors = [more/less] maximal response
more
Higher affinity for hormone = [more/less] likely to get a response
more
What is maximum response
a further increase in hormone will elicit no more response
Define sensitivity
the concentration of hormone producing 50% of maximal response
If more hormone is required to get 50% response, sensitivity [increases, decreases]
decreases
In what two ways can sensitivity be changed?
change number of receptors
affinity of receptors
What does down-regulating mean?
decreasing sensitivity
either the number or affinity of receptors decreases even when hormone concentrations are high*
In down-regulation, there is a(n) [increase/decrease] of new receptors, and a(n) [increase/decrease] in degradation of existing receptors leading to [activation/inactivation] of receptors
decrease
increase
inactivation
What is an example of down-regulation?
T3 down-regulates TRH receptors in anterior pituitary
What does up-regulating mean?
increasing sensitivity
either the number or affinity of receptors increase
In up-regulation, there is a(n) [increase/decrease] of new receptors, and a(n) [increase/decrease] in degradation of existing receptors leading to [activation/inactivation] of receptors
increase
decrease
activation
What is an example of up-regulation?
GH increases its receptors in skeletal muscle and liver
What is the general mechanism of hormone action?
hormone recognized and binds to membrane receptor
hormone receptor complex either coupled to signal-generating mechanism OR acts as one itself
generated signal (2nd messenger)
When the hormone is recognized and binds to a membrane receptor, it forms a _______ complex
hormone-receptor complex
Hormone-receptor complexes are what two forms?
coupled to a signal-generating mechanism
OR
acts as a signal-generating mechanism itself
The generated signal (2nd messenger) affects intracellular process in what two ways?
alter activity
OR
alter concentration of functional/structural proteins
Where are receptor systems?
cell membrane or within cell
What are the types of hormone receptor systems?
classic cell membrane systems
catalytic cell membrane receptor systems
intracellular receptor systems
How are classic cell membrane receptor systems classified?
classified according to membrane receptor structure
OR
second messenger system used
- rapid response
Do catalytic cell membrane receptor systems use a second messenger system? If not, what do they use?
NO
enzyme system such as kinases
- usually a rapid response
What do intracellular receptor systems use?
cytoplasmic or nuclear receptors
- SLOW
T/F: G-proteins are coupling molecules use in almost all membrane receptor systems
TRUE
What are G-proteins composed of?
heterotrimeric proteins (3 subunits)
G-proteins are [activated/inactivated] when GTP is bound, [active/inactive] when GDP is bound
active
inactive
G-proteins can be ______ & _______
stimulatory
inhibitory
G-proteins are linked to one of two second messenger systems. What are they?
adenylyl cyclase w/ cAMP
phospholipase C w/ IP3/Ca2+
Adenylyl cyclase (enzyme) is linked with which second messenger?
cAMP
Phospholipase C (enzyme) is linked with which second messenger?
IP3/Ca2+
In the adenylyl cyclase system, GTP binds G protein and activates _____. The 2nd messenger, ______, is produced and activates ________. Intracellular proteins are phosphorylated by __________, causing physiologic actions
adenylyl cyclase
cAMP
protein kinase A
protein kinase A
In the phospholipase C system, GTP binds G protein and activates ______ which liberates _________ and _________ from ________. The second messenger, ______ causes [Na+/Ca2+/K+] release from ER or SR stores. _________ and ___________ activates __________, which phosphorylates proteins
phospholipase C
DAG and IP3
IP2
IP3
Ca2+
Ca2+ and DAG
protein kinase C
What uses the catalytic receptor system?
ANP (anthill natriuretic peptide)
NO
What is the catalytic receptor system?
catalytic receptors on cell surface associated with enzymes on intracellular side
What enzymes are part of the catalytic receptor systems?
guanylyl cyclase enzyme
serine/threonine kinase enzymes
receptor tyrosine kinases
Define receptor tyrosine kinases
tyrosine kinase activity WITHIN the receptor itself
has 3 domains
when hormone binds, intracellular portion of receptor phosphorylates itself
monomer and dimer types
What does then extracellular domain of receptor tyrosine kinases do?
binds hormone
What does then intracellular domain of receptor tyrosine kinases do?
where tyrosine kinase activity occurs
What are the 3 domains of receptor tyrosine kinases?
extracellular domain
transmembrane domain
intracellular domain
What is the monomer type of receptor tyrosine kinases?
receptor is going to dimerize AFTER hormone binds
- tyrosine kinase is activated and phosphorylates tyrosine on itself
What is the dimer type of receptor tyrosine kinases? Give two examples
receptor is already a dimer
- insulin & IGF (insulin-like growth-factor 1)
What are tyrosine kinase-associated receptors?
associate with other proteins that have tyrosine kinase activity - Janus kinase family
T/F: The intracellular portion of tyrosine kinase-associated receptors cannot phosphorylate itself
TRUE
Steroid hormones use _________ systems and use either _______ or _________
intracellular receptor
cytosolic OR nuclear receptors
Steroids initiate DNA [transcription/translation] and synthesis of new proteins
transcroption
Steroid hormones diffuse across the membrane and binds receptor in _____ or _______
cytosol
nucleus
What are steroid-responsive elements?
specific DNA sequences in target genes
once the steroid diffuses and binds to a receptor, the receptor undergoes a conformational change. The complex binds to these steroid-responsive elements
After the complex binding to the steroid-responsive elements, the complex is now a ______ factor, and _____ is transcribed, translation occurs, new proteins, physiologic actions
transcription
mRNA
