Chapter 2: Transporters, receptors, and enzymes Flashcards
P450 inhibitors: STICKFACES.COM Group
S - Sodium valproate
T - Ticlodipine
I - Isoniazid
C - Cimetidine
K - Ketoconazole
F - Fluconazole
A - Acute alcohol/amiodarone
C - Ciprofloxacin
E - Erythromycin
S - Sulfonamides
C - Cranberry juice
O - Omeprazole
M - Metronidazole
Group = grapefruit juice
P450 Inducers: BS CRAP GPS
B - Barbiturates
S - St. John’s Wort
C - Carbamazepine
R - Rifampin
A - Alcohol (chronic)
P - Pheytoin
G - Griseofulvin
P - Phenobarbital
S - Sulfonylureas
6 most important P450 enzymes
1A2
2B6
2D6
2C9
2C19
3A4
Serotonin transporter and gene family
presynaptic monoamine SERT/SLC6
Norepinephrine transporter/gene family
presynaptic monoamine NET/SLC6
Dopamine transporter/gene family
presynaptic monoamine DAT/SLC6
glial and GABA transporters
GAT1-4
GlyT1-2
EAAT1-5
GAT1-4 gene family/substrate
SLC6/GABA
GlyT1-2 gene family/substrate
SLC6/Glycine
EAAT1-5 gene family/substrate
SLC1/glutamate and aspartate
vesicular neurotransmitter transporters VMAT1-2 gene family/substrate
SLC18/serotonin
dopamine
histamine
norepinephrine
VaChT vesicular transporter gene family/substrate
SLC18/acetylcholine
VIAAT vesicular transporter gene family/substrate
SLC32/GABA
vGluT1-3 vesicular transporter gene family/substrate
SLC17/glutamate
false substrate for SERT
MDMA
false substrate for NET
dopamine, epinephrine, amphetamine
false substrate for DAT
norepinephrine, epinephrine, amphetamine
how do transporters concentrate monoamines into presynaptic neurons (reuptake)
sodium-potassium ATPase continually pumps sodium out of the cell to create a downhill gradient that allows for the uphill transport of the neurotransmitter
how do vesicular transporters package neurotransmitters into synaptic vesicles
proton ATPase continually pumps positively charged protons out of the vesicles so that the neurotransmitter can be transported into the vesicle to keep the charge the same
what is a neurotransmitter transporter
a type of receptor that binds to neurotransmitter prior to transporting it across the membrane
2 major classes of plasma membrane transporters
sodium/chloride-coupled transporters (SLC6 gene family)
Glutamate transporters (SLC1)
plasma membrane transporters on presynaptic membranes
SERT
NET
DAT
plasma membrane transporters located on glia and neuronal cells
GAT1-4
BGT1
Gly T1-2
EEAT1-5
SLC6 sodium/chloride-coupled includes which plasma membrane transporters
includes transporters for serotonin, norepinephrine, and dopamine as well as the neurotransmitter GABA and amino acid glycine
presynaptic SLC6 transporters
SERT
NET
DAT
glial SLC6 transporters
GAT1-4
BGT1
GlyT1-2
SLC1 glial transporter
EAAT1-5 (glutamate)
3 subclasses of intracellular synaptic vesicle transporters
SLC18
SLC32
SLC17
what are the two types of molecular transporters
plasma membrane transporters
intracellular synaptic vesicle transporters
SLC18 intracellular synaptic vesicle transporters
VMAT1-2 (vesicular monoamine transporters)
VAChT (vesicular acetylcholine transporter)
which monoamines are transported VMAT1-2 intracellular synaptic vesicle transporters
serotonin
norepinephrine
dopamine
histamine
SLC32 gene family intracellular synaptic vesicle transporters
VIAATs (vesicular inhibitory amino acid transporters)
SLC17 gene family intracellular synaptic vesicle transporters
VGluT1-3 (vesicular glutamate transporters)
false substrate for SERT presynaptic transporter
MDMA (Ecstasy)
false substrates for presynaptic transporter NET
dopamine
epinephrine
amphetamine
false substrates for presynaptic transporter DAT
norepinephrine, epinephrine, amphetamine
synaptic vesicle transporter for all 3 monoamines
VMAT2 (vesicular monoamine transporter 2)
what are the 3 monoamines
sertraline
dopamine
norepinephrine
does it take energy to concentrate monoamines into presynaptic neuron?
yes
how is energy generated to concentrate monoamines into the presynaptic neuron
downhill transport of sodium coupled with uphill transport of the monoamine
what does “the sodium pump” (adenosine triphosphatase) do to generate the energy to concentrate monoamines in the presynaptic neuron
continuously pumps sodium out of neuron creating a downhill gradient which creates an uphill gradient for the monoamine
binding sites on SLC6 transporters
2 sodium ion binding sites
other binding sites for drugs (SSRIs)
what happens when a drug binds to a receptor on an SLC6 transporter
prevents monoamine reuptake
what binds to the SLC6 transporter in the absence of sodium
nothing; not sodium or monoamine
how do you increase monoamine action
prevent it from binding to its transporter so it accumulates in the synapse
which transporters are blocked by ADHD stimulants and cocaine
DAT
NET
which tra
nsporters are blocked by most drugs for unipolar depression
SERT
NET
DAT
what conditions are treated by blocking neurotransmitter transporters
anxiety, fibro neuropathic pain, postherpetic neuralgia, peripheral neuropathy and other pain conditions, eating disorders, impulsive-compulsive disorders, OCD, trauma/stress related disorders (PTSD)
what condition are NOT treated by blocking monoamine binding to transporters
bipolar depression with mixed features
what is the only medication that blocks GABA transporter GAT1 to increase synaptic GABA concentration
anticonvulsant tiababine
what happens when glutamate is transported into glia
it is converted into glutamine to enter the presynaptic neuron for conversion back to glutamate
differences of SLC1 to SLC6 transporters
glutamate is excitatory
exact location on pre/post synaptic neurons/glia is under investigation.
no drugs are known to block them
glutamate transport almost always has countertransport of potassium.
may work as timers rather than dimers
transporters for neurotransmitter histamine
no presynaptic transporter
vesicular transporter is VMAT2 (same as monoamines)
histamines inactivation
entirely enzymatic
VMATs vesicular transporters are members of what gene family
SLC8
VaChT
vesicular transporter for acetylcholine
VIAAT is a vesicular transporter that is a member of what gene family
SLC32
what gene family does vesicular transporter vGluT1-3 belong to
SLC17
vesicular transporter for glutamate
SV2a transporter
novel vesicular transporter with 12 transmembrane regions that binds to anticonvulsant levetiracetam whic may reduce seizures by blocking neurotransmitter release
how is energy generated to move neurotransmitters into synaptic vesicles
proton ATPase (proton pump) pumps positively charged protons out of synaptic vesicles continuously.
neurotransmitters are able to then concentrate against the gradient by substituting their own + charge in the vesicle for the + charge being pumped out
SO
neurotransmitters go in while protons go out, keeping the charge in the vesicle the same
which vesicular transporters are NOT known to be targeted by drugs
ones for GABA (SLC32), acetylcholine (SLC18), and glutamate (SLC17)
which vesicular transporters are targeted by many drugs
VMATs (SLC18 family)
drugs that target VMAT vesicular transporters
amphetamine (both monoamine and vesicular transporters)
methylphenidate and cocaine (only monoamine transporters)
tetrabenzine and its derivatives as inhibitors
structure of G-protein-linked receptors
7 transmembrane regions (spans membranes 7 tiems) that cluster around a central core that contains a neurotransmitter binding site
how do drugs lead to modification of g-protein-linked-receptors
they mimick or block neurotransmitter function that normally happens at binding or allosteric sites on the receptor
difference between neurotransmitters and drugs on g-protein-linked receptors
neurotransmitters interact with all receptor subtypes. Drugs interact only with a specific receptor subtype
action of agonists on g-protein-linked receptors
turns on the synthesis of the second messenger to the greatest extent possible so downstream proteins are fully phosphorylated and genes are maximally expressed
what are the 2 ways to stimulate G-protein-linked receptors with full agonist action
drugs bind directly to neurotransmitter sites
or indirectly boost levels of the neurotransmitters themselves
2 ways drugs boost levels of neurotransmitters themselves
inhibition of monoamine transporters
blocking enzymatic destruction of neurotransmitters
2 ways to block enzymatic destruction of neurotransmitters
inhibition of SERT, NET, DAT and GABA transporter GAT1
inhibition of enzyme acetylcholinesterase
action of antagonist on g-protein-linked receptors
produces conformational change in receptor that causes signal transduction to remain at constitutive levels
clinical purpose of antagonists on g-protein-linked receptors
block excessive neurotransmission
reverses agonists, partial agonists, and inverse agonists
action of partial agonists on g-protein-linked receptors
produce signal transduction that is more than constitutive but less than agonist depending on how close the partial agonist is to the full agonist
action of inverse agonist on g-protein linked receptors
causes conformational change to stabilize receptor in inactive form
essentially, turning action down below consitutive
what happens when an enzyme is bound
it cannot bind with its substrate so it is inactivated
can be reversible or irreversible
irreversible binding of an enzyme
cannot be displaced by the substrate (essentially killing it)
reversible binding of an enzyme
when a substrate can compete for the receptor site and shove it off of the enzyme
few drugs that bind enzymes used in clinical practice
MAOIs
acetylcholinesterase
glycogen synthase kinase (GSK)
agents that target GSK enzymes that are used in clinical practice
lithium may target in this enzyme in the signal transduction pathway of neurotrophic factors
what acts through phosphoprotein GSK-3 to promote cell death
neurotrophins, growth factors, and other signaling pathways
it is also possible that valproate and ECT act of GSK3
consequences of inhibiting GSK3
may have neuroprotective actions, long term plasticity, and may contribute to mood stabilizing effects of lithium
what are CYP enzymes
drug metabolizing enzymes that are mediated through the liver and gut that are responsible for a large amount of psychotropic drugs
are pharmacokinetics or pharmacodynamics responsible for mechanism of action of psychotropic drugs
pharmacodynamics
6 most important CYP450 enzymes
1A2
2B6
2D6
2C9
2C19
3A4
extensive metabolizers
people who have “normal” rates of drug metabolism by CYP4550 enzymes
what happens if there is reduced activity of CYP450 enzymes
risk for elevated drug levels as they are not metabolized fast enough
patients need less than standard doses
ultra-rapid metabolizers
people who have elevated CYP450 enzyme activity
consequences of being an ultra-rapid metabolizer
may require higher than standard doses due to resultant subtherapeutic drug levels