5. GPCR (G protein-coupled receptor)
Ø Seven-helix transmembrane; N-terminal in the extracellular side and C-terminal in
cytosol;
Ø C-terminal: Ser- and Thr-rich;
Ø G protein-coupled when activated.
Extracellular loop
Intracellular loop
6. ØDue to their abundance and significant roles in signal
transduction and cellular regulation, GPCRs
participate in the regulation of a variety of
physiological functions, such as smell, taste, vision,
secretion, metabolism, nerve system regulation,
immune response, cellular differentiation, and
embryonic development.
ØConsequently, the malfunction of GPCRs results in
many diseases, such as diabetes, obesity,
cardiovascular disease, neurodegenerative disorders,
inflammation, and cancer, making these receptors
important drug targets.
GPCRs are important signal receptors
ions, photons, hormones, neurotransmitters,
odors, lipids, large proteins, mechanical force......
7. GPCRs: the most complex family of receptors
Ø largest family of cell
surface receptors
Ø Structure diversity
Ø Widely expressed
- Family A - Rhodopsin
- Family B – Secretin + Adhesion
- Family C - Glutamate
- Family F - Frizzled
Nat Rev Drug Discov. 2013 Jan;12(1):25-34.
8. Cells express a large number of GPCRs
0
1
2
3
5
9
DIV
K25 survival) / K5 (apoptosis)
Changes during development
Changes during cell condition
10. Drugs targeting to GPCRs
Nat Rev Drug Discov. 2017;16(12):829-842.
Ø There are currently 475 drugs (~34% of all drugs approved by the FDA) that act
on 108 unique GPCR targets.
Ø Approximately 321 agents are currently in clinical trials, of which ~20% target 66
potentially novel GPCR targets that do not currently have an approved drug.
Ø Biological drugs, allosteric modulators and biased agonists are becoming more
frequent in clinical trials.
Ø The major disease indications for GPCR modulators show a shift towards
diabetes, obesity and Alzheimer disease, although other central nervous system
disorders are also highly represented.
Ø The 224 (56%) non-olfactory GPCRs that are yet to be explored in clinical trials
have broad untapped therapeutic potential, particularly in genetic and immune
system disorders.
11. History of Nobel Prize winners in the field of
GPCR research
Rhodopsin
neurotransmitter GPCR
second messenger
G protein
GPCR antagonist
GPCR agonist
odorant GPCR
GPCR structure and G protein-
independent pathway
Millstones in GPCR field!
12. "for their discoveries concerning the primary physiological and
chemical visual processes in the eye."
Ragnar
Granit
Haldan Keffer
Hartline
George
Wald
1967 Nobel Prize
13. Rhodopsin
Ø Rhodopsin is a G-protein coupled receptor, and is the most abundant protein in the rod cells found in the retina.
Ø It functions as the primary photoreceptor molecule of vision, and contains two parts: an opsin molecule linked to
a chromophore, 11-cis-retinal.
Ø The opsin molecule is comprised of 348 amino acids, and has seven transmembrane domains.
Ø Rhodopsin is synthesized in the rough endoplasmic reticulum of the inner segments of photoreceptors and
subsequently undergoes posttranslational modifications in the Golgi before becoming functional.
14. Rhodopsin: phototransduction
Hydrolysis of cGMP causes cation channels to close, preventing depolarization induced by the influx of
Na + and Ca2+ . Rod cell membrane hyperpolarizes.
Photons are converted into chemical signal then electrical signal.
Front. Neurosci., 2020
Guanylyl cyclase: 鸟苷酸环化酶；PDE: phosphodiesterase, 磷酸二酯酶
16. Earl W.
Sutherland,
Jr.
1971 Nobel Prize
for his discoveries concerning the
mechanisms of the action of
hormones“, especially
epinephrine (肾上腺素), via
second messengers, namely
cyclic adenosine monophosphate,
or cyclic AMP.
cAMP signaling pathway
- Gs-coupled GPCRs;
PKA
AC
cAMP-PDE
Adenylyl cyclase: 腺苷酸环化酶；PDE: phosphodiesterase, 磷酸二酯酶
17. The Nobel Prize in Chemistry 2012
"for studies of G-protein-coupled receptors"
Robert J. Lefkowitz (1943-)
Howard Hughes Medical Institute,
Duke University Medical Center,
Durham, NC, USA
Brian K. Kobilka (1955-)
Stanford University School of Medicine,
Stanford, CA, USA
Detailed characterizations of the sequence,
structure and function of the β-adrenergic and
related receptors, discovery and
characterization of GPCR kinases (GRK) and
β-arrestins.
Determined the molecular structure of the β2-
adrenergic receptor.
Crystallized β2-adrenergic receptor/G protein
complex.
18. Adrenergic Receptors
• Adrenergic Receptors are targets of the catecholamine, especially norepinephrine and
epinephrine.
• Many cells possess these receptors, and the binding of a catecholamine to the receptor
will generally stimulate the sympathetic nervous system.
• The sympathetic nervous system is responsible
for the fight-or-flight response, which includes
widening the pupils of the eye, mobilizing
energy, and diverting blood flow from non-
essential organs to skeletal muscle.
• Categories:
– α-ARs: α1, α2
– -ARs: 1, 2, 3
(β-adrenoceptor)
19. Difficulties for GPCR structure
Expression
Low abundance of GPCRs at the cell surface; Difficulties in correct
folding……
Purification
7TM domain stability, large extracellular domain, dimer…..
Analyze
Computational expansion and dissemination
20. Brian K. Kobilka (1955-)
Stanford University School of Medicine,
Stanford, CA, USA
½ The Nobel Prize in Chemistry 2012
Determined the molecular structure of the
β2-adrenergic receptor.
Crystallized β2-adrenergic receptor/G
protein complex.
21.
22. Robert J. Lefkowitz (1943-)
Howard Hughes Medical Institute,
Duke University Medical Center,
Durham, NC, USA
Detailed characterizations of the sequence,
structure and function of the β-adrenergic and
related receptors, discovery and
characterization of GPCR kinases (GRK) and
β-arrestins.
24. Richard Henderson
1/3 2017 Nobel Prize in Chemistry
“for developing cryo-electron microscopy for the
high-resolution structure determination of
biomolecules in solution”
Subramaniam, Henderson,
Nature, 2000
Unwin and Henderson,
Nature 1975
Bacteriorhodopsin
29. Apo Agonist
Agonist
+ PAM
Agonist
+ G protein
Antagonist
Antagonist
+ NAM
Agonist
+ PAM
+ G protein
Active state is defined as G protein-bound or
agonist-bound and opened intracellular TM bundle.
Inactive state is defined as antagonist-bound and
antagonist and NAM-bound.
Active
Inactive Intermediate
30. Nat Rev Drug Discov. 2013;12(1):25-34
The GPCR Network: a large-scale collaboration to
determine human GPCR structure and function
37. History of Nobel Prize winners in the field
of GPCR research
Rhodopsin
neurotransmitter GPCR
cAMP, the secondary messenger
G protein
GPCR antagonist
GPCR agonist
GPCR structure and transduction
odorant GPCR cAMP
G
GPCR
Millstones in GPCR field!
38. Knowledge points summary
Ø GPCR
Ø Important finding in GPCR history
Ø cAMP
Ø GPCR structure determination
Ø AlphaFold
Ø High throughput drug screening
39. GPCRs: the most complex family of receptors
Ø largest family of cell
surface receptors
Ø Structure diversity
Ø Widely expressed
- Family A - Rhodopsin
- Family B – Secretin + Adhesion
- Family C - Glutamate
- Family F - Frizzled
Nat Rev Drug Discov. 2013 Jan;12(1):25-34.
44. Angiotensin II type 1 receptor (AT1R)
Class A GPCR examples:
Angiotensin II receptor type 1 or AT₁
receptor is the best characterized
angiotensin receptor.
It has vasopressor effects and regulates
aldosterone (醛固酮) secretion.
It is an important effector controlling
blood pressure and volume in the
cardiovascular system.
Angiotensin II receptor antagonists are drug
s indicated for hypertension,
diabetic nephropathy and congestive
heart failure (糖尿病肾病与充血性心力衰竭).
50. CCR5 / CXCR4 and HIV infection
Complex CD4 and co-receptor
(CCR5 or CXCR4)
Per Johan Klasse (2012) Cell Microbiol
51. GPCRs: the most
complex family of
receptors
- Family A - Rhodopsin
- Family B – Secretin + Adhesion
- Family C - Glutamate
- Family F - Frizzled
Nat Rev Drug Discov. 2013 Jan;12(1):25-34. 乙酰胆碱
神经降
压素
腺苷
组胺
白三烯
内皮细胞
分化因子
受体
加压素
受体
Mas-related GPCR
嘌呤(ATP,ADP,UTP)
速激肽
受体
凝血酶
受体
前列
腺素
53. GLP-1R: Glucagon-Like Peptide-1 Receptor
a major therapeutic target for the treatment of type 2 diabetes
Nature, 2017
Overall structure of the GLP-1R TMD
Class B GPCR examples:
54. 33 receptors
«Adhesion» receptors
Class B GPCR examples:
N-terminal fragment (NTF): extracellular NTF generated by the autoproteolytic cleavage of the GAIN
domain.
C-terminal fragment (CTF): membrane-spanning C-terminal fragment generated by the autoproteolytic
cleavage of the GAIN domain.
GPCR Autoproteolysis Inducing (GAIN) domain:An evolutionarily conserved domain (~320 amino
acids) shared by adhesion G protein-coupled receptors and polycystic kidney disease proteins. The
GAIN domain is both necessary and sufficient for receptor autocleavage.
GPCR proteolysis site (GPS) motif Langenhan T, et al. Nat Rev Neurosci. 2016. PMID: 27466150 Review.
55. Structural basis for the tethered peptide activation of adhesion GPCRs
https://doi.org/10.1038/s41586-022-04619-y
Tethered peptide activation mechanism of the adhesion GPCRs ADGRG2 and ADGRG4
https://doi.org/10.1038/s41586-022-04590-8
Structural basis of tethered agonism of the adhesion GPCRs ADGRD1 and ADGRF1
https://doi.org/10.1038/s41586-022-04580-w
The tethered peptide activation mechanism of adhesion GPCRs
https://doi.org/10.1038/s41586-022-04575-7
Four Nature
paper in 2022
2+3+4+2=11
Cryo-EM
structures
56. GPCRs: the most
complex family of
receptors
- Family A - Rhodopsin
- Family B – Secretin + Adhesion
- Family C - Glutamate
- Family F - Frizzled
Nat Rev Drug Discov. 2013 Jan;12(1):25-34.
57. Class C GPCRs
• Calcium-sensing receptor-related (CaS)
• Metabotropic glutamate receptors (mGluR)
• GABAB receptors
• RAIG (Retinoic acid-inducible orphan G PCRs)
• Taste receptors
• Orphan receptors: ligands are not identified yet
66. GABAB and medication
Pre- and clinical studies have shown GABA transmission and GABAB receptor play
a modulatory role in the mechanism of action of drugs of abuse (in particular
alcohol addiction).
Pathology Drugs Phase
spasticity Agonist (baclofen : Lioresal) Commercial
drug addiction Agonist (CGP44532) Development
pain Agonist (CGP35024) Development
narcolepsy Partial agonist (GHB : Xyrem) Commercial
anxiety PAM (CGP7930) Development
Alzheimer Antagonist (SGS-742) Phase II
epilepsy Antagonist (CGP35348) Development
Foster and Kemp, 2005
Jacobson and Cryan, 2008
GABA
Baclofen
GABAB is a G protein-coupled receptor for GABA
date rape drug
GHB
g-hydroxybutyric acid
67. Baclofen in drug addiction
ü Poor blood-brain barrier penetrance
ü Short half-life (3-4 h)
ü Fast tolerance
ü Secondary effects (sedative effect, headache)
baclofen (Lioresal®)
Anti-spasticity
drug
Ameisen et al., Alcohol & Acoholism, 2005
Addolorato et al., Alcohol 2009
baclofen to treat addiction in particular alcohol relapse
GABA
