TLRs Flashcards
1
Q
What repeats do all TLRs possess?
A
Amino-terminal leucine rich repeats (LRR)
2
Q
What are LRRs responsible for?
A
Recognition of P(M)AMPs
3
Q
What is the carboxy-terminal of TLRs?
A
Toll-interleukin-1 receptor (TIR) domain
4
Q
What is the TIR in TLRs for?
A
Initiating intracelllular signalling
5
Q
How many TLRs in humans and mice?
A
10 in humans
12 in mice
6
Q
What TLRs are conserved in humans and mice?
A
TLRs 1-9
7
Q
What TLRs are not functional in mice?
A
TLR10
8
Q
What TLRs do not occur in the human genome?
A
TLR11, 12 and 13
9
Q
What TLR is the ligand unclear for?
A
TLR10
10
Q
Which TLR only works as a heterodimer?
A
TLR2
11
Q
What can TLR2 form heterodimers with?
A
TLR1 or 6
12
Q
Which TLRs can form homodimers?
A
3, 4, 5, 7, 8, 9
13
Q
Which TLR binds LPS?
A
TLR4
14
Q
What can TLR1 and 2 bind to?
A
Triacyl lipopeptide
15
Q
What specific pathogen can TLR2-6 recognise?
A
Mycobacteria
16
Q
What is TLR2 normally recognising?
A
Gram positive bacteria
Fungi
Mycobacteria
17
Q
What does TLR5 bind?
A
Flagellum
18
Q
What does TLR3 bind?
A
DsRNA
19
Q
What type of nucleic acid is bound by TLR7 and 8?
A
SsRNA
20
Q
What nucleic acid is bound by TLR9?
A
DNA
21
Q
What TLR only signals through myd88?
A
TLR5
22
Q
What are the 3 regions of LPS?
A
O region
R region
Lipid A region
23
Q
What is the O region of LPS?
A
Polysaccharide
24
Q
What is the R region of LPS?
A
Core polysaccharide
25
What type of affinity does TLR4 have for LPS?
Low affinity - it requires other proteins to recognise LPS
26
What proteins does TLR4 require to recognise LPS?
LBP
CD14
MD2
27
What do MD2 and TLR4 do?
Form a heterodimer that represent functional LPS receptor
28
What does CD14 do?
Enhances the sensitivity to LPS
29
What do 5 of the 6 acyl chains of lipid A interact with?
A hydrophobic pocket present in MD2 within the TLR4-MD2 heterodimer
30
What does the sixth acyl chain of lipid A interact with?
With a different TLR4 molecule
31
Where does binding of TLR4 to MD-2 occur?
At the concave face of the TLR4 extracellular domain
32
What receptors promote delivery of PAMPs to TLR2?
CD14, CD36 and MbL
33
What proteins promote CpG DNA delivery to endosome-localised TLR9?
DNA-binding proteins HMGB1 and RAGE
34
How many lipid chains do you need for most efficient binding of LPS to TLR4?
6 lipid chains with 12-14 carbons each
35
What is the process of CD14 and TLR-4 Endocytosis?
CD14 mediates TLR4 Endocytosis and interferon expression
CD-14 induced Endocytosis occurs independently of TLR4 signalling
36
What other TLRs can CD14 help?
TLR3 - facilitates uptake of poly I:C into TLR3 endosome
TLR7 and 9 - acts as a coreceptor for TLR7 and 9 to promote their signalling
37
What does TLR2 collaborate with?
TLR1 and TLR6
38
what does TLR2 with TLR1/6 do?
Discriminates between triacyl and diacyl lipopeptides respectively
39
Why is purity of reagents really important?
Because there was a study that was activating TLRs and they thought it was serum amyloid A but it was actually the contaminating proteins
40
What receptors recognises flagellin?
TLR5
41
What are the endosomal TLRs?
TLR3, 7, 8 and 9
42
What TLR recognises dsRNA?
TLR3
43
What innate immune cells is TLR3 not highly expressed in?
Neutrophils and plasmacytoid DCs
44
What is TLR-3 deficiency in humans associated with?
Herpes simplex virus type 1
45
What is an analogue of dsRNA?
Poly I:C
46
How many binding sites do TLRs 7,8,9 have?
Two binding sites
47
What does TLR9 bind?
DNA
48
What does TLR7 and 8 bind?
SsRNA
49
When is TLR7 dimerisation most efficient?
In the presence of ssRNA and free guanosine molecules
50
When is TLR8 dimer formation most efficient?
In the presence of ssRNA and free uridines
51
When is TLR9 dimer formation most efficient ?
Presence of CpG-containing DNA and free cytosines
52
What happens to TLR3, 7, 8 and 9 when in endosome?
They are cleaved within their leucine-rich-repeat containing ectodomains
Both fragments remain associated with one another and are important for inflammatory activity of these receptors
53
Which TLR doesn’t function the same in mice and humans?
TLR8 - so it is less well studied than TLR7
54
What is TLR9 highly expressed on?
Plasmacytoid dendritic cells
55
What is TIRAP/MAL?
A peripheral membrane protein that surveys the inner leaflets of the plasma and endosomal membranes
56
What does TIRAP/MAL signal through?
an N-terminal phosphoionsitide binding domain
57
What does TIRAP/MAL contain at its C terminus and what does it do?
Contains a TIR domain
Recognises dimerised TIR domains of most TLRs
58
What is the TIR domain essential for in TIRAP/MAL?
Signalling by TLRs 2, 4, 7 and 9
59
What is a SMOC?
A supramolecular organising centre that is assembled following detection of TIR domain dimerisation
60
What does IRAK stand for?
IL-1 receptor associated kinase
61
What does TLR and MyD88 association recruit?
IRAK4 that autophosphorylates and phosphorylates IRAK1/2
62
What does the MyD88 complex formation do?
Induces association with E3 ubiquitin ligase TNF receptor-associated factor 6 ( TRAF6)
63
What are the 3 pathways triggered through MyD88 mediated signalling?
- NFkappaB activation
- MAPkinases
- glycolysis
64
How is nfkappab activated through MyD88 signalling?
TRAF6 complexes with TAK1 complex comprising of TAK1. TAK1 then associated with IKK leading to phosphorylation of IKKb, triggering the pathway
65
How are MAP kinases activated with MyD88 signalling?
Activation of upstream MAP kinases for Erk1 and 2, p38 and JNK which activate transcription factors AP-1 and CREB
66
How does activation of glycolysis occur from MyD88 signalling?
TRAF6 recruits kinase TBK1 that induces glycolysis through phosphorylation of AKT that phosphorylates hexokinase
67
What do all endosomal TLRs need to be transported to the endosome?
A chaperone
68
What is the only TLR that will never be affected by MyD88 deficiency?
TLR3
69
What is gamma interferon only produced by?
NK cells and Th1 cells
70
what is type 1 interferon produced by?
Every cell
71
What is the only adaptor used by TLR-3?
TRIF
72
What is TRIF essential for?
Induction of genes encoding type I IFNs and IFN-stimulated genes in response to TLR-4
73
What adaptor does TLR4 require?
TRAM
Upon detection of dimerised TLR4 in endosome, TRAM interacts with TRIF
74
What does TRIF-dependent signalling in response to TLR4-LPS lead to?
Upregulation of cos-stimulatory molecules and MHCII in DCs through production of type I IFNs
75
What is a negative regulator of MyD88?
IRAKM
76
What is a key negative regulator of TLRs?
A20
77
What happens if someone has a defect in MyD88?
They are not as sick as expected, are susceptible to a particular group of pathogens
