Toll-Like Receptors

Question 1

1. Define: Pathogen Associated Molecular Pattern (PAMP) and Pathogen Recognition Receptor (PRR).

Answer 1

Pathogen Associated Molecular Pattern (PAMP):

• components of microbe, not host
• PAMPs are specfic like components of foreign moleclues

Pattern Recognition Receptors (PRRs)
-recognize microbial PAMPs
-distinguish self from non self
-can be secreted, on cell surface, or intracellular
Functions include:
-activation of pro-inflammatory signaling
-opsonization
-coagulation
-apoptosis
-complement activation
-phagocytosis

CACA PO
Coagulation, Apoptosis, complement activation, activation of proinflamatory signaling, phagocytosis, Opsinization

Ex) TLRs, NOD proteins, RIG-i-family

Question 2

2. Match different Toll-like receptors (TLRs) with their cognate PAMPs

Answer 2

First of all, what is a toll-like receptor TLR:

• they are PRRs that recognize diverse group of PAMPs
• 10 in humans
• most recognize multiple structrually unrelated PAMPs

Triacyl lipopeptide ( G +bacteria):

• TLR1
• TLR2

Diacyl lipopeptide (G+ bacteria):

• TLR2
• TLR6

dsRNA(viruses):
-TLR3 (probs a dimer)

GRAM NEG Bacteria LPS:
-TLR4 ( moves from the surface to the endosome)

ilidazoquinolines ssRNA (virus):
-TLR7/8

CpG DNA Hemozoin:
-TLR9

GRAM NEG Bacteria Flagellin:
-TLR5

Profilin-like protein uropathogenic bacteria:
-TLR11

• TLRs that recognize bacteria or fungi are on the cell surface
• TLRs that recognize DNA or RNA are in the endosome (so essentially TLR3,7,8,9)

Question 3

3. Describe the basics of Toll-like receptor signaling pathways.

Answer 3

Pathogen–> TLR–>Adapters–>Cytokines

Question 4

4. List examples of key genes and pathways activated by TLR signaling.

Answer 4

Genes induced by TLR Signaling:
INNATE:
-Inflamatory cytokines
-Chemokines
-Antimicrobials

ADAPTIVE:

• MHC
• Co-stimulatory molecules

-Lets look at a specific example with TLR4 signaling because it uses pretty much all of the pathways that the other TLRs could use and is found on both the cell surface and endosome. (which uses Myd88 on the cell surface and TRIF when in the endosome).

Taking a close look at the Myd88-dependent pathway located on the cell surface:
•LPS stimulates TLR4‐MD2 dimerization
• Myd88 is recruited
• Myd88 recruits kinases IRAK‐4, IRAK‐1,
IRAK‐2
• The ubiquitin ligase Traf6 recruited
• Traf6 activates the MAPKKK TAK1
• TAK1 activates the p38, ERK, and JNK
MAPKs
• This activates the AP‐1 transcription
factor
• TAK1 also activates the IKK complex,
which phosporylates IkB
• IkB is then ubiquitinated and
degraded
• This releases NFkB, which translocates
to the nucleus
 --> turns on activation of pro-inflamatory cytokines

Here is my story to remember it: its interesting to say the least:
-Mr. LPS is a very fat man who is so fat he cant see his own dick.
He says he will give TLR4-MD2 a DIME* if it can show him MyDick88.
-BUT he must do it in the religiously conservative area of the IRAK4,1,2 triangle.
-While he is there he must TRAFic TAK1s(the delicious treat enjoyed by latinos everywhere) to the racist group MAPKKK which then will activate AP-1
- TAK1*s must also go to the IKK complex
-IKK then phosphorylates Ikb which gets ubiquinated and then degraded
-This allows NFkB to go to the nucleus and cause inflamation through cytokines.

Sorry the story kind of broke down at the end but at least i know the pathway now..

Question 5

5. Explain the importance of subcellular localization of TLRs.

Answer 5

For example, Intracellular localization of TLR9 facilitates access to
viral DNA but prevents recognition of self DNA
Helps prevent autoimmune disease!!!

so they added tlr9 to the membrane surface and it attacked itself.

It goes back to what Ross from Friends was trying to tell us. That whole jeckell and hyde bullshit. we want these things to work but to much activation is bad. so we keep it subcellularly to prevent that bad autoimmune response.

Wheres rachel itzam?

Question 6

6. Explain, and provide examples of, how TLR signaling is relevant for human infectious and inflammatory disease

Answer 6

oh gosh here we go..
-so he started talking about this experiment that knocked out this thing called Unc93b1, which is a transport protein, that moves TLRs to endosomal vesicles;
they fucked with the transport protein and nothing went to where it needed to go

• Some kids have mutations in TLR3 that recognizes dsRNA ,and these kids will get Herpes Simplex Virus Encephalitis.
• But it turns out ( read in Ross boring paleontology voice) people with mutations in transport proteins like Unc93b1 also get HSV encephalitis. crazy world right. because TLR3 isnt going to the right place

(In short)
-Two children with Herpes Simplex Virus
Encephalitis have mutations in TLR3
-But mutations in genes that regulate
TLR3 transport/localization also affect human disease

its good temporarily to fight

Question 7

7. Provide examples of how TLR agonists can be used therapeutically

Answer 7

TLR Agonists:

• Enhancing immunity to infectious disease
• Enhancing vaccine efficacy (adjuvant)
• old people flu;melanoma;HIV

Ex1)Enhancing Influenza Vaccination in Seniors With TLR
Agonists

Ex2)TLR‐Ligand Matured Dendritic Cell Vaccination in
Melanoma Patients

Ex3)Toll‐like Receptor 9 Agonist Treatment in Chronic HIV‐1
Infection

Question 8

8. Provide examples of how TLR antagonists can be used therapeutically

Answer 8

TLR Antagonists:
-Treating acute (ie – sepsis) inflamation
-Treating chronic (ie‐ asthma)
inflammatory diseases

Ex1)
A 12‐week Dose‐Ranging Trial in Patients With Moderate
to Severe Plaque Psoriasis (TLR7/8/9 inhibitor)
“it may take you 7,8,9 times to spell plaque psoriasis”

Ex2)
The Effect of TLR4 Inhibition in Obese and Type 2 Diabetic Subjects
“type 2 diabetes is bad enough but if your obese its like twice as bad so 2x2= TLR”4”

Ex3)
TLR‐9 Antagonism in Steroid Resistant Optic Neuritis