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TGF β signaling, GIPC, binds to its PDZ domain, which prevents its proteosomal degradation, which subsequently increases TGFβ activity. It may also serve as an
inhibin coreceptor to ActivinRII
[9]
.
BMP and Activin membrane bound inhibitor (BAMBI), has a similar extracellular domain as type I receptors. It lacks an intracellular serine/threonine protein kinase
domain and hence is a pseudoreceptor. It binds to the type I receptor preventing it from being activated. It serves as a negative regulator of TGF beta signaling and
may limit tgf-beta expression during embryogeneis. It requires BMP signaling for its expression
FKBP12 binds the GS region of the type I receptor preventing phosphorylation of the receptor by the type II receptors. It is believed that FKBP12 and its homologs
help to prevent type I receptor activation in the absence of a ligands, since ligand binding causes its dissociation.
[edit] R-SMAD regulation
[edit] Role of inhibitory SMADs
There are two other SMADs which complete the SMAD family, the inhibitory SMADs (I-SMADS), SMAD6 and SMAD7. They play a key role in the regulation of
TGF beta signaling and are involved in negative feeback. Like other SMADs they have an MH1 and an MH2 domain. SMAD7 competes with other R-SMADs with
the Type I receptor and prevents their phosphorylation
[9][14]
. It resides in the nucleus and upon TGF beta receptor activation translocates to the cytoplasm where it
binds the type I receptor. SMAD6 binds SMAD4 preventing the binding of other R-SMADs with the coSMAD. The levels of I-SMAD increase with TGF beta
signaling suggesting that they are downstream targets of TGF-beta signaling.
[edit] R-SMAD ubiquitination
The E3 ubiquitin-protein ligases SMURF1 and SMURF2 regulate the levels of SMADs. They accept ubiquitin from a E2 conjugating enzyme where they transfer
ubiquitin to the RSMADs which causes their ubiquitination and subsequent proteosomal degradation. SMURF1 binds to SMAD1 and SMAD5 while SMURF2 binds
SMAD1, SMAD2, SMAD3, SMAD6 and SMAD7. It enhances the inhibitory action of SMAD7 while reducing the transcriptional activities of SMAD2.
[edit] Summary table
TGF Beta superfamily ligand Type II Receptor
Type I receptor
R-SMADs
coSMAD
Ligand inhibitors
Activin A
ACVR2A
ACVR1B (ALK4)
SMAD2 , SMAD3
SMAD4 Follistatin
GDF1
ACVR2A
ACVR1B (ALK4)
SMAD2 , SMAD3
SMAD4
GDF11
ACVR2B
ACVR1B (ALK4), TGFβRI (ALK5) SMAD2 , SMAD3
SMAD4
Bone morphogenetic proteins BMPR2
BMPR1A (ALK3), BMPR1B (ALK6) SMAD1 SMAD5, SMAD8 SMAD4 Noggin, Chordin, DAN
Nodal
ACVR2B
ACVR1B (ALK4), ACVR1C (ALK7) SMAD2 , SMAD3
SMAD4 Lefty
TGFβ
s
TGFβRII
TGFβRI (ALK5)
SMAD2 , SMAD3
SMAD4 LTBP1, THBS1, Decorin
Tumor necrosis factor receptor
From Wikipedia, the free encyclopedia
(Redirected from TNF receptor)
Jump to: navigation, search
TNFR/NGFR cysteine-rich region
Structure of the soluble human 55 kd TNF receptor-human TNF beta
complex
[1]
.
Identifiers
Symbol
TNFR_c6
Pfam
PF00020
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InterPro
IPR011614
PROSITE
PDOC00561
SCOP
1tnr
[show]
Available PDB structures:
A tumor necrosis factor receptor (TNFR), or death receptor, is a cytokine receptor that binds tumor necrosis factors (TNF).
Because "TNF" is often used to describe TNF alpha, "TNFR" is often used to describe the receptors that bind to TNF alpha - namely, CD120. However, there are
several other members of this family that bind to the other TNFs.
[2][3]
Contents
[hide]
•
1 Members
•
2 References
•
3 Further reading
•
4 External links
[edit] Members
Family members include:
[2]
Type
Protein
Aliases
Gene
CD120a
TNFRSF1A
1 (CD120)
CD120b
TNFRSF1B
3
Lymphotoxin β receptor
TNFRSF3
LTBR
4
CD134
TNFRSF4
5
CD40
TNFRSF5
CD40
FAS
TNFRSF6
FAS
6
TNFRSF6B
TNFRSF6B
7
CD27
TNFRSF7
CD27
8
CD30
TNFRSF8
9
CD137
TNFRSF9
TNFRSF10A
DR4
TNFRSF10A
TNFRSF10B
DR5
TNFRSF10B
TNFRSF10C
TNFRSF10C
10
TNFRSF10D
TNFRSF10D
RANK
TNFRSF11A
11
Osteoprotegerin
TNFRSF11B
12
TNFRSF12A
TNFRSF12A
TNFRSF13B
TNFRSF13B
13
TNFRSF13C
TNFRSF13C