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Signal transduction
Intracellular (nuclear)
receptors
webversion
Dimension of time and solubility
Role of intracellular receptors in
signal transduction
protein
5’
3’
steroid-thyroid-retinoidreceptor superfamily
Nuclear hormone receptor
superfamily
Steroid-thyroid-retinoid- receptor
superfamily
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•
•
•
Development
Differentiation
Cell-cell interactions
Nutrient sensing
Some ligands of the steroid-thyroid-retinoid
receptor superfamily
„prereceptorial” activation of hormones - biotransformation
Module 1: Figure aldosterone and cortisol biosynthesis
Cell Signalling Biology
www.cellsignallingbiology.org
2007
Steroid-thyroid-retinoid- receptor superfamily
~ 150 protein (caterpillar – human)
similar structure – regulation of transcription
ligands:
hormones
vitamins
drugs, fatty acids
lipid soluble
binding to
regulation
DNA
ligand
other transcription factors
ligand dependent
non receptor factors
Principal mechanism of action of steroid hormones
AF1
LBD - AF2
DBD
A/B
C
Helix 12
D
E/F
Nuclear Hormone Receptor
Superfamily
Type I family
Type II family
Steroid family
Non-steroid family
GR
PR
AR
MR
ER a, b
TR a, b
RAR a, b, g
RXR a, b, g
VDR
PPAR a, g, d
CAR, SXR/PXR
LXR a, b, FXR
AF1
LBD - AF2
DBD
A/B
Helix 12
C
D
E/F
Nuclear Hormone Receptor
Superfamily
Type I family
Type II family
Steroid family
Non-steroid family
GR
PR
AR
MR
ER a, b
TR a, b
RAR a, b, g
RXR a, b, g
VDR
ER
GR
GR
HRE
homodimer
PPAR a, g, d
CAR, SXR/PXR
LXR a, b, FXR
AF1
LBD - AF2
DBD
A/B
C
Helix 12
D
E/F
Nuclear Hormone Receptor
Superfamily
Type I family
Type II family
Steroid family
Non-steroid family
GR
PR
AR
MR
ER a, b
TR a, b
RAR a, b, g
RXR a, b, g
VDR
RXR TR
HRE
heterodimer
PPAR a, g, d
CAR, SXR/PXR
LXR a, b, FXR
Orphan receptors
unknown
LIGAND
sequence homology
unknown
FUNCTION
more than 40 orphan subfamilies
ligand „candidates”
small
lipofilic
retinoids
terpenoids
farnesol
long chain fatty acids
PGJ2 analogues
Steroid receptors
GR
GR
RXR heterodimers
RXR
RAR
GR glucocorticoid
MR mineralocorticoid
PR progesteron
AR androgenic
ER estrogen
TRab thyroid hormone
RARabg trans RA
VDR 1,25 – (OH)2 – VD3
PPARabg eicosanoids
(peroxisome proliferator activated receptor)
EcR ecdyson
RXRabg 9 cisz RA, terpenoids
Consensus sequences of DNA response elements for different
nuclear hormone receptors
The glucocorticoid receptor and oestrogen
receptor bind to their respective response
elements as homodimers. The response
element is an inverted repeat
The vitamin D receptor, the thyroid hormone
receptor and the retinoic acid receptor bind to
their respective response elements as
heterodimers (with RXR). The response
element is an direct repeat.
The spacing between
these repeats determines the specificity of
the interaction.
Fig 11.42 Lodish et al. Molecular Cell Biology
Similar structure, different length
Conserved domains of transcription factors in nuclear-hormone
receptor superfamily
A/B
AF-1 domain
C
Two non-repeating
C4 Zn finger motif
E
AF-2 domain
Fig 11.41 Lodish et al. Molecular Cell Biology
Structure of nuclear receptors 2.
A/B variable
connections with
coactivators
transactivators
proteins of transcription
DBD conservative
binding to HRE
two Zn fingers
DNA binding
dimerisation
(a helix dimerisation)
DBD structures
Zinc Finger
HOOC
N
Y
K H
V
R
Q
C
H
R
S
L
A
S
C6
H
C
E
R
K
C2H2
C5
H Zn
C
E
V
Finger type
C4
C
K
G
L
Zn
NH2
S
F
Transcription Factors
Gal4 C6
Steroid hormone C4 + C6
Structure of nuclear receptors 2.
A/B
variable
connections with
DBD conservative
binding to HRE
two Zn fingers
coactivators
transactivators
proteins of transcription
DNS binding
dimerisation
(a helix dimerisation)
LBD
ligand binding with high affinity (KM > 1 nM)
selective, stereospecific, reversible
hsp
C terminal part
protein binding
transactivator
dimerisation
translocation
D possible change of conformation „folds”
translocation
hinge function
Hsp90 - GR
Steroid type
Steroid or hsp90
Steroid or hsp90
Grouping according to the localisation of the receptor (1)
A. steroid type
GR, AR, PR, MR, ER
longer A/B domain
associated to hsp when no ligand is bound
no HRE binding without ligand
but repressor effects
importance of LBD
must dimerise for HRE binding
activation domains
agonist, antagonist binding sites (different)
no silencer effect
Grouping according to the localisation of the receptor (2)
B. Thyroid type
TR, RAR, VDR, RXR, PPAR, orphan
short A/B domen
no hsp association
binds to HRE without ligand
silencer effect
can bind as a monomer
thyroid type
Modulating factors
1. presence of ligands
2. activation without ligands
3. receptor phosphorylation
4. structure of binding site – chromatin structure
5. nuclear non-receptor transcription factors
Modulating factors
presence of ligands
ligand metabolism
(e.g. metamorphosis, prostate: dihydrotestosterone production
enhanced AR effect)
activation without ligands
effect of neurotransmitters on sexual behaviour
dopamine PR, ER, VDR activating effect
effect of growth factors
EGF activates ER – it can be prevented by antiestrogens
„crosstalk” membrane receptor
nuclear receptor
Modulating factors
receptor phosphorylation
multiple sites
presumably (also) after DNA binding
nuclear DNA-dependent protein kinases
needed for transactivation?
roles
needed for receptor transport?
activation without ligands?
structure of binding site – structure of chromatin
the order of heterodimer according to the binding site
RXR - TR
TR - VDR
size of the „interface”
„half binding site”
hormone-induced changes in DNA conformation
alteration of nucleosome structure
Chromatin-based mechanisms
Histone deacetylases (HDAC) corepressors since they don’t
recognize DNA directly but are recruited by association
with sequence-specific, DNA-binding proteins. HDAC
cleaves the acetyl moiety from histone tails.
Thyroid hormone receptor (TR) provides an example of a
DNA binding protein that switches activity by changing its
associated cofactor.In the absence of thyroxin, TR
associates with a target gene but inhibits transcription
because TR recruits an HDAC complex.Thyroxin induces
a conformational change upon binding TR and causes
dissociation of the HDAC and association of a HAT
complex. This contributes to transcriptional activation.
General Scheme for Activation of Gene Transcription
by Nuclear Hormone Receptors
Robyr, Wolffe, Wahli
Mol. Endocrinol 2000
Therapeutic implications
GLUCOCORT ICOID HORMONE (DEX) RECEPT OR (GR)
ACT IVAT ION OF A GR RESPONSIVE GENE
RNA Polymerase II
GRE
Hormone Regulated Gene
GR
GR
DEX
DEX
+1
NUCLEUS
Gene
T ranscription
GR
GR
DEX
DEX
GR
HSP90
CYT OPLASM
HSP70
DEX
DEX
p23
EST ROGEN (E) RECEPTOR (ER)
ACT IVAT ION OF AN ER RESPONSIVE GENE
RNA Polymerase II
ERE
E
ER
Hormone Regulated Gene
ER
+1
E
NUCLEUS
E
ER
Gene
T ranscription
ER
E
ER
HSP90
HSP70
CYT OPLASM
E
E
p23
T HYROID HORMONE RECEPT OR ACTIVATION OF A
T 3 RESPONSIVE GENE
RNA Polymerase II
TRE
RXR T3R
T3 Regulated Gene
+1
T3
NUCLEUS
Gene
T ranscription
T3
CYT OPLASM
T3
T3
VIT AMIN D (V) RECEPT OR (VDR)
ACT IVAT ION OF A VDR RESPONSIVE GENE
RNA Polymerase II
VDRE
Hormone Regulated Gene
+1
RXR VDR
V
NUCLEUS
Gene
T ranscription
RXR VDR
V
VDR
CYT OPLASM
V
V
Receptor deficiency
Nuclear receptor mutations (LBD, DBD)
familiar diseases
X-linked AR mutation
testicular feminisation
no androgen response
glucocorticoid resistance
hypercortisolism without Cushing symptomes
vitamin-D-resistent rachitis
TR mutations in LBD
rare syndromes ?
Therapeutic significance of receptor detection
mamma carcinoma
ER
leukemias
lymphoid tumors
uterus tumors
GR
antisteroids:
antiestrogen therapy
no dissociation
competition
inhibition of dimerisation
tamoxifen
antiestrogen
ER ligand research: osteoporosis, mamma carcinoma, menopausa
VDR ligand research: osteoporosis, prostate carcinoma,