at the University of Pécs and at the University of Debrecen Identification number

at the University of Pécs and at the University of Debrecen

Identification number: TÁMOP-4.1.2-08/1/A-2009-0011

G-PROTEIN-LINKED RECEPTORS

Tímea Berki and Ferenc Boldizsár Signal transduction

Medical Biotechnology Master’s Programmes

at the University of Pécs and at the University of Debrecen

Identification number: TÁMOP-4.1.2-08/1/A-2009-0011

Nomenclature

• G-protein-coupled receptors (GPCRs)

• Seven-transmembrane domain receptors

• 7-TM receptors

• Heptahelical receptors

• Serpentine receptor

• G protein-linked receptors (GPLR)

Ligand-binding Gα C-terminal tail Other Gα surfaces Helix 8 (Gβ-binding)

Gα -binding

Interaction surface

IL1 IL2 IL3

EL1 EL2 EL3 Extracellular loops (EL1-3)

Intracellular loops (IL1-3)

N

C

GRK phosphorylation (Desensitization) PKC phosphorylation

(Desensitization)

PKC phosphorylation (Desensitization) Palmitoylation

(Lipid raft localization) N-Glycosylation

(Receptor folding, trafficking)

E/DRY Motif (Receptor activity and protein-protein interactions)

Plasma membrane

TM 1

TM 2

TM 3

TM 4

TM 5

TM 6

TM 7

Transmembrane helix (TM1-7)

TM 4

7-transmembrane-spanning

receptors (7-TM)

GPCR

Structure of 7-TM receptors

Side perspective

Intracellular persective

TM 1

TM 4

TM 5 TM

6 TM

7

IL 1

IL2

IL3 EL1

EL2 EL 3

N

C ^TM ₂

TM 3

Intracellular loops

Extracellular loops

TM 1

TM 2

TM

3 TM

4 TM

5 TM

6 TM

7

IL1

IL3

EL1 EL2

EL3 N

C

Ga-binding surface Non-covalent

bond

IL2

TM 1

TM

2 TM

4 IL1

IL2

IL3

EL1

EL2 N EL3

C

TM 7

TM 6

TM 3

TM 5 Ga

TM 1

TM 5 TM TM 6

7

N

C

TM 4 TM

2 Gα

TM 3

Ga C-terminal

tail of Ga

Agonist

Active GPCR

Inactive GPCR

GPCR subtypes

• Class A (or 1) – Rhodopsin-like

• Class B (or 2) – Secretin receptor family

• Class C (or 3) – Metabotropic glutamate/pheromone

• Class D (or 4) – Fungal mating pheromone receptors

• Class E (or 5) – Cyclic AMP receptors

• Class F (or 6) – Frizzeled/Smoothened

GDP b  a

b  GTP

a GTP

b  a

GDP b  a

Plasma membrane

Cytoplasm

GDP GTP G-protein coupled receptor

(GPCR)

Signal molecule

Inactive G-protein

Activated G-protein subunits

GTP b  a

Activation of G-protein-coupled

receptors (GPCR)

GDP b  a

b 

GTP Gia

G-protein coupled receptor (GPCR)

Phospholipases Ion channels

Activates Rho

Ion channels PI3K Phospholipases Adenylyl cyclases Receptor kinases GTP

Gsa

GTP Gqa

GTP G_12/13a GTP

a

Ca²⁺

PLC

PIP₂ DAG

IP₃ cAMP

Adenylyl cyclase ATP

cAMP Adenylyl

cyclase ATP

Plasma membrane

Cytoplasm

G-proteins

G-protein heterotrimer

Catecholamine hormon synthesis

CO ₂ ^–

+ H ₃ N

OH Tyrosine

Tyrosine hydroxylase

CO ₂ ^–

+ H ₃ N

OH Dihydroxy

phenilalanine (L-DOPA)

OH DOPA

decarboxylase

Dopamine

+ H ₃ N

OH OH

Dopamine β-hydroxylase

Dopamine

+ H ₃ N

OH

HO OH Phenethanolamine

N-methyltransferase

Epinephrine N

OH OH HO

H ₂ ⁺

H ₃ C

Epinephrine and analogues

HO HO

OH

CH₃ H N

Epinephrine (adrenaline)

Tyramine HCL HO

NH₂ .HCL

OH

CH₃ H N

Ephedrine sulphate CH₃

2

.H₂SO₄

Pseudoephedrine HCL OH

CH₃ H N CH₃

.HCL

Dexamfetamine sulfate NH₂ CH₃

2

.H₂SO₄

Amfetamine sulfate NH₂ CH₃

2

.H₂SO₄

Phenylethanolamine sulfate NH₂ OH

2

.H₂SO₄

Isoprenaline HCL N

OH

.HCL HO H

HO

CH₃ CH₃

Orciprenaline sulfate N

OH H HO

OH

CH₃

CH₃ .H₂SO₄

2

.H₂SO₄

2

Salbutamol sulfate N OH H

HO CH₃

CH₃ HO

CH₃

.H₂SO₄

2

Terbutaline sulfate N OH H

CH₃ CHCH_{3 3} HO

OH

cAMP-PKA pathway

PO₄ gated channel Gα gated

channel

cAMP gated channel

Receptor

Inactive PKA Activated

PKA GTP

b  a

Adenylyl cyclase

R R

C C cAMP cAMP cAMP

cAMP R

R C C

C C R

cAMP cAMP

cAMP R cAMP

CRE CREB

cAMP Response Element

Gene expression P

CREB P CREB ATP cAMP

GTP a

Nucleus P cAMP

GTP a

P

ADP ATP

Primary Action of Epinephrine in a Liver Cell

Acetylcholine

Stress signal Fuel for „fight or flight”

Protein Kinase A

Glucose-6- Phosphatase

Pyr Kinase Fructose-2,6-

bisphosphatase

Pyruvate PEP Fructose-1,6-

bisP Fructose-6-P Fructose-2,6-bisP

Fructose-1,6-

bisphosphatase PFK-1

Glucose-6-P Glucose

Glucose-1-P Glycogen

Glucogen Phosphorylas

e Glucogen Synthase

P

P

P

Phosphorylas e Kinase A

P

P

cAMP ATP

Adenylate Cyclase

GDP b  a_s

Epinephrine

Receptor

Glucagon signaling

PANCREAS Glucose low in blood

Protein Kinase A

Glucose-6- Phosphatase

Pyr Kinase Fructose-2,6-

bisphosphatase

Pyruvate PEP Fructose-1,6-

bisP Fructose-6-P Fructose-2,6-

bisP

Fructose-1,6-

bisphosphatase PFK-1

Glucose-6-P Glucose

Glucose-1-P Glycogen

Glycogen Phosphorylas

e Glycogen Synthase

P

P

P P

cAMP ATP

Adenylate Cyclase

GDP b  a_s

Glucagon

(Epinephrine)

Receptor

Serotonin receptor

Serotonin receptor → G-protein → adenylyl cyclase

→ ATP → cAMP → PKA → cAMP Response

Element (CRE) → Gene expression

Types of serotonin receptor

Family Mechanism Potential

5-HT1 Decreasing cellular levels of cAMP Inhibitory

5-HT2 Increasing cellular levels of IP3 and DAG Excitatory

5-HT3 Depolarizing plasma membrane Excitatory

5-HT4 Increasing cellular levels of cAMP Excitatory

5-HT5 Decreasing cellular levels of cAMP Inhibitory

5-HT6 Increasing cellular levels of cAMP Excitatory

5-HT7 Increasing cellular levels of cAMP Excitatory

Receptor desensitization

GRK

ATP ADP

Arrestin

P P P P P

P

G-protein linked receptor kinase

Activated receptor Desensitized receptor