LEC 2 Flashcards
INTRACELLULAR RECEPTORS what are characteristics of drugs that bind to intracellular receptors (2)
- hydrophobic
2. lipid soluble
INTRACELLULAR RECEPTORS what is mech of action
- drug crosses PM
- drug binds intracellular receptor
- receptor displaces HSP to expose DNA binding site
- receptor translocates to nucleus
- receptor binds to DNA
- receptor activates transcription of target gene
INTRACELLULAR RECEPTORS what are characteristic effects of drug binding to intracellular receptor
- slow onset
2. long lasting
G PROTEIN (TRANS MEM) what are G protein subunits
- alpha
- beta
- gamma
G PROTEIN (TRANS MEM) what happens at rest
- GDP bound to G alpha
2. G alpha bound to recepotr
G PROTEIN (TRANS MEM) what happens when ligand binds to recepotr
GDP GTP excahnge
G PROTEIN (TRANS MEM) what does GTP GDP exchange result in
- G alpha unbinds from receptor + acts as effector
- G beta gamma unbinds from receptor + acts as effector
G PROTEIN (TRANS MEM) what is molecular timer mech referring to
G alpha hydrolyzes GTP to return sys to rest
G PROTEIN (TRANS MEM) what happens to G beta gamma after unbinding from receptor
remains associated w PM
G PROTEIN (TRANS MEM) what are 3 G alpha subtypes
- G s
- G i
- G q
G PROTEIN (TRANS MEM) what does Gs target
adenylyl cyclase to activate
G PROTEIN (TRANS MEM) what does Gi target
adenylyl cyclase to inactivate
G PROTEIN (TRANS MEM) what does Gq target
phospholipase C to activate
G PROTEIN (TRANS MEM) what does G alpha have indirect effect on
first components of signalling cascade
G PROTEIN (TRANS MEM) what is Gs mech (7)
- agonist binds to receptor
- receptor changes conformation
- GTP bound Gs activates AC
- AC converts ATP to cAMP
5 cAMP activates protein kinase A - protein kinase A phosphorylates substrate
- phosphorylates substrate generates biological response
G PROTEIN (TRANS MEM) what is Gi mech (7)
- agonist binds to receptor
- receptor changes conformation
- GTP bound Gi inhibits AC
- suppress cAMP
- suppress protein kinase A
- suppress phosphorylated substrate
- suppress biological response
G PROTEIN (TRANS MEM) what is Gq mech
- agonist binds receptor
- receptor undergoes conformational change
- GTP bound Gq activates PLC
- PLC hydrolyzes PIP2 ==> PIP3 and DAG
PIP 3
a. IP3 binds to ER
b. ER releases Ca
c. Ca binds to calmodulin
d. Ca-calmodulin complex binds to effector protein
e. effector protein generates biological response
DAG
a. DAG activates protein kinase C
b. protein kinase C phosphorylates substrate
c. phosphorylated substrate generates biological response
TKR (TRANS MEM) what happens when ligand binds to TKR
- dimerization
- phosphorylation ==> each other
- phosphorylation ==> substrate
TKR (TRANS MEM) what makes TKR diff from G protein
TKR acts as kinases
INTRACELLULAR VS MEM BOUND what is circulating form of drug
- intracellular ==> bound
2. mem bound ==> variable
INTRACELLULAR VS MEM BOUND what is speed of response
- intracellular ==> slow
2. mem bound ==> fast
INTRACELLULAR VS MEM BOUND why is speed of response slow for intracellular (2)
- requires DNA binding
2. requires activating target genes
INTRACELLULAR VS MEM BOUND how fast is termination of signal
- intracellular ==> slow
2. mem bound ==> fast
INTRACELLULAR VS MEM BOUND why is termination slow for intracellular(2)
- large reserve of bounddrug
2. gene expression is slow to reverse
ION CHANNEL what is fastest mech for signalling
ion channel
ION CHANNEL what happens when ions cross PM
change in mem voltage
ION CHANNEL what are 2 types
- ligand gated ion channel
2. voltage gated ion channel
ION CHANNEL what is ligand gated ion channel
pore in channel opens in response to binding of ligand
ION CHANNEL what is voltage gated ion channel
pore in channel opens in response to changing of voltage
what is on x axis of conc response curves
conc
what is on y axis of conc response curves
effect
what relationship exists bw agonist conc and effect
saturating
what is E max
max biological effect
what is EC50
conc of drug that produces 50% E max
what are2 ways of plotting conc
- linear scale
2. log
what does linear scale result in
saturating response
what does log scale result in
sigmoidal response
what does efficacy refer to
mag of E max
what does large efficacy mean
what does small efficacy mean
- large efficacy ==> high Emax
- small efficacy ==> low Emax
what does potency refer to
EC50
what does weakly potent mean
high EC50, large concentration of drug required to generate half Emax
what does strongly potent mean
low EC50, low concentration of drug required to generate half Emax
what is full agonist
binds to receptor to generate E max
what is partial agonist
binds to receptor to generate partial E max
what is antagonist
binds to receptor to generate no effect (on own)