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Lecture 8

Biology 2382B Lecture Notes - Lecture 8: Arginine, Blood Vessel, Phosphodiesterase


Department
Biology
Course Code
BIOL 2382B
Professor
Sashko Damjanovski
Lecture
8

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G-PROTEIN COUPLED RECEPTORS
GPCRs and second messengers
second messengers include: cAMP, cGMP, IP3, Ca2+
GPCRs are involved in:
oglycogen metabolism
odevelopment and disease
oarteriole smooth muscle relaxation
oexploited by pathogens
whooping cough, cholera
oexploited by drug companies
sildenafil, Levitra etc.
oexploited by drug dealers
meth, heroin, ecstasy etc.
G-protein coupled receptors & signal transduction
GPCRs are protein receptors which sense
molecules outside the cell and activate inside
signal transduction pathways and ultimately,
cellular responses
When a ligand binds to the GPCR it causes a
conformational change in the GPCR, which
allows it to then activate an associated G
protein by exchanging its bound GDP for a GTP.
The G protein's α subunit, together with the
bound GTP, can then dissociate from the β and γ
subunits to further affect intracellular signaling
proteins or target functional proteins (effectors)
directly depending on the α subunit type
oGs (stimulant), Gi (inhibitor) + Gt specifically found in membrane of rod cells
all our senses are dependent on GPCRs and their signal pathways
Effector enzyme is activated/inhibited by active G-protein (α subunit + GTP)
ogenerates second messenger
GPCRs have 7 transmembrane domains
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G-protein Coupled Receptors
usually 7 transmembrane spanning
800-1000 types
ligands are diverse
olight, lipids, odors, neurotransmitters, hormones, pheromones
present everywhere
major target of pharmaceutical drugs (~60%)
over 282,000 hits on PubMed
Intracellular Second Messengers
produced by effector enzymes
pay attention to function not structure
Signal Amplification
each step of the signaling cascade activates more and more proteins until an end result
is achieved
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find more resources at oneclass.com

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How GPCRs work
Use of FRET
CFP is tethered to G α subunit while YFP is tethered to the β and γ subunits
if FRET shows yellow fluorescence then that means that the G protein is inactive (GDP
bound) meaning the α, β and γ subunits are together
owhich means the GCPR is inactive (ligand unbound)
find more resources at oneclass.com
find more resources at oneclass.com
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