Transcript Dectin 1

Signaling through C-type lectin
receptors: shaping immune response
Teunis B. H. Geijtenbeek and Sonja I. Gringhuis
Nature Reviews: Immunology, Vol. 9, July 2009, p.465-479
report by: Yuri Yakushko
Talk overview
1. Dendritic cells
2. Pathogen recognition
3. C-type lectins classification
4. CLR signaling in general
5. CLRs that interact with TLRs (DC-SIGN)
6. CLRs that interact with TLRs (BDCA2)
7. CLRs that interact with TLRs (DCIR, MICL)
8. TLR-independent signaling by CLRs (dectin 1)
9. TLR-independent signaling by CLRs (dectin 2 and mincle)
10. CLRs and T-cells differentiation
11. Therapeutic potential
12. Future directions. Sum up
DCs:
• located throughout the body
• capture and process antigens
• present antigens with:
• MHC I for CD8+ cells
• MHC II for CD4+ cells
Myeloid dendritic cells Most similar to monocytes. mDC are made up of at least two
(mDCs)
subsets:
(1) the more common mDC-1, which is a major stimulator
of T cells
(2) the extremely rare mDC-2, which may have a function
in fighting wound infection
Plasmacytiod dendritic Look like plasma cells, but have certain characteristics similar
cells (pDCs)
to myeloid dendritic cells.
Picture source: www.healthsystem.virginia.edu
Dendritic cells
Section of skin showing large numbers of dendritic (Langerhans) cells in the epidermis.
CD1a staining
www.dermatologyoutlines.com/dermcdmarkers.html
Dendritic cells
CD4+ cell
IFNγ that activates
macrophages to fight
intracellular infections
Regulatory T cell
Suppress effector T-cells
Some subpopulations of
T-suppressors:
• CD8+ cells
• CD4, CD25 and Foxp3
(CD4+CD25+ regulatory T cells
are exclusively called "Tregs")
IL-17 to mobilize
phagocytes to clear
extracellular fungi and
bacteria
IL-4, IL-5, IL-13 to induce
humoral immune response
(e.g. against helminths)
Pathogen recognition
PAMP – pathogen-associated
molecular patterns: groups of pathogens
that share similar structures
PRR – PAMP Recognition Receptors:
1. Toll-like receptors (TLRs):
• 1,2,4,5,6,10,11 on cell surface
• 3,7,8,9 in cell compartments
2. non-TLRs:
• retinoic acid-inducible gene I (RIG-I)
• C-type lectin receptors (CLRs)
C-type lectins
Lectins are sugar-binding proteins
which are highly specific
for their sugar moieties
Ca2+-independent lectins
C-type lectin receptors (CLRs)
bind particular sugars
in Ca-dependent manner
Ca2+-dependent lectins
C-type lectin-like molecules
bind either carbohydrates,
polypeptide ligands or both.
• have at least one carbohydrate-recognition domain
• can be cytoplasmic or transmembrane
• some of them function as PRR (pathogen-associated
molecular patterns (PAMP) recognition receptors)
C-type lectin receptors
CLRs
Both families of receptors can recognize mannose, fucose, glucans etc.
• mannose allows recognition of viruses, fungi and mycobacteria
• fucose structures are usually expressed by bacteria and helminths
• glucans are present on mycobacteria and fungi
mannose-receptor family
(e.g. DEC 205)
asialoglycoprotein-receptor
family (e.g. DC-SIGN, dectin 1)
Ag internalization, processing
and presentation (on DC)
Some CLRs are expressed be several subsets of DCs:
DC-SIGN and dectin 1 on subepithelial and some myeloid DCs
Other CLRs are specific for particular DC subsets:
• langerin (=CLEC4K=CD207) on Langerhans cells (e.g. epedermis),
• BDCA2(=CLEC4C) on plasmacytoid DCs
C-type lectin receptors, pathogen recognition
and signaling
C-type lectin receptors, pathogen recognition
and signaling
Ag-processing via CLRs on dendritic cells
1
1
2
2
1
2
1
3
• CLRs are targeted in vaccine studies to increase Ag-specific immune
responses: DEC205 was one of the first targets in these studies
• CLEC9A is expressed on mouse CD8+ cells and recognized necrotic cells.
1 When bound to ligand, activates SYK (spleen tyrosine kinase) 2
for cross-presentation of necrotic cell-associated Ag 3
Cross-presentation means presenting
Ag with MHC I to CD8+ cells
CLRs signaling
CLRs
signaling
through
ITAM/ITIM-containing
adaptor molecules
(e.g.Fc-receptor γ-chain (FcRγ)
and DAP12)
Protein kinases or phosphatases
that direclty or indirectly interact
with their cytoplasmic domains
• mincle
• dectin 2
• BDCA2
ITAM – immunoreceptor tyrosin-based activation motif
ITIM – immunoreceptor tyrosin-based inhibition motif
•
•
•
•
dectin 1
DC-SIGN
DCIR
MICL
CLRs signaling
CLRs
ITAM / ITIM-containing adaptor
molecules or
pKs/phosphatases
??
NF-kB
(nuclear transcription factor)
inducible gene expression
in the immune system
CLRs signaling and TLRs pathways
1. BDCA2, DC-SIGN, DCIR, MICL can modulate TLR-induced
gene expression (but only when they are activated by their
specific PRR). All these molecules do not effect gene
expression without signals, induced by other PRRs.
2. Dectin 1, dectin 2, mincle do not interact with TLRs
signaling. But they can induce gene expression without other
PRRs.
CLRs that interacts with TLRs pathways
Mannose-containing pathogens
(e.g. M. tuberculosis, HIV-1,
C. albicans, measles virus)
1
2
1
3
DC-SIGN activation
TLR4
2
4
TLR3
TLR5
Ras (GTPase)
Nf-kB
3 +
RAF1
(Ser/Thr kinase)
?
RAF1-GTP
5
4
Src and PAKs
kinases
RAF1-P
Dendritic cells-sprecific ICAM3-grabbing non-integrin
(DC-SIGN) signaling
5
?
NF-kB
Histone
acetyltransferase
: increases DNA
binding activity
of NF-kB p65
subunit
RAF1-P
1
?
1
NF-kB: subunit p65+P
2
2
4
3
CBP
(CREB-binding protein)
CREB
(cAMP response
element binding)
+
3
CBP + CREB + NF-kB + DNA complex
DNA regions called CRE
(cAMP response elements)
4
Transcriptional activation
of il8 and il10 promoters
Dendritic cells-sprecific ICAM3-grabbing non-integrin
(DC-SIGN) signaling
• IL8
• IL10
DC-SIGN signaling. Sum up
DC-SIGN
?
Ras + RAF1
MEK-MAPK/ERK cascade
Nf-kB + CREB-CBP + DNA
il8, il10
genes expression
RAF1-MEK-MAPK/ERK-cascade not launched
by DC-SIGN (but by anti-DC-SIGN antibody)
RAF1-MEK-MAPK/ERK-cascade launched by
some DC-SIGN ligands (peanut allergen Ara h1
or Schistosoma mansoni egg Ag)
gp120 of HIV-1 is linked to ERK activation,
but DC-SIGN role not proved
Ixodes scapularis protein (“Salp15”):
• activates RAF1, but downstream cascade
does not involve p65 (of Nf-kB).
• MEK is activated, but not the following ERK.
DC-SIGN signaling plasticity
Ixodes scapularis
1
1
Ras – RAF1 - MEK
?
mRNA decay
mRNA
1
3
il6 and Tnf genes
2
TLR
3
2
1
Borrelia burgdorferi
2
So DC-SIGN signaling is of high plasticity
and poorly understood. So guys, work more:)
I.scapularis spreads B.burgdorferi
that causes Lyme disease (borreliosis)
MAPK
pathways
http://www.genome.jp/kegg/pathway/hsa/hsa04010.html
or http://www.kegg.jp
BDCA2 signaling through ITAM-containing FcRγ
BDCA2
Fc-receptor γ-chain,
bound with ITAM
+ 2P
1 +
2
1
FcRγ-ITAM-PP
3
2
SYK (spleen tyrosine kinase)
4
3
?
Ca2+
TLR pathway
4
BDCA2 – Blood DC antigen 2 protein
ITAM – immunoreceptor tyrosin-based activation motif
complex
BTK (Bruton’s tyrosine kinase)
BLNK (B-cell linker)
PLCγ2 phospholipase
BDCA2 signaling through ITAM-containing FcRγ
1. Tonic Ca2+ signaling also inhibits TLR pathway via activating
calcineurin (phosphatase). Calcineurin then inhibits MYD88
(myeloid differentiation primary response protein 88).
2. Thus BDCA2, perhaps, also inhibits MYD88 (and downstream
TLR-induced pathway) through calcineurin.
3. In macrophages Ca2+ signaling is induced by TREM2
(triggering-receptor expressed on myeloid cells 2), that also
binds to ITAM-proteins and down-regulates TLR-signaling.
CLR signaling through ITIMs
DCIR and MICL are the only known CLRs that contain ITIM
in their cytoplasmic tails
Both molecules are not shown to induce immune responses on their own,
but can modulate signaling pathways induced by other PRRs
ITIM – immunoreceptor tyrosin-based inhibitory motif
DCIR signaling
DCIR (with ITIM tail)
1
SHP1 or SHP2
1
2
3
?
2
3
3
DCIR – DC immunoreceptor
3
SH2-domain
containing
protein tyrosin
phosphatases
TLR9-induced
IFNα and TNF production
by plasmacytiod DCs
TLR8-mediated
IL-12 and TNF production
by myeloid DCs
MICL signaling
MICL (with ITIM tail)
1
1
2
SHP1 or SHP2
2
SH2-domain
containing
protein tyrosin
phosphatases
ERK?
3
?
TLR-induced
IL-12 expression
MICL – myeloid C-type lectin like receptor
ERK – extracellular signal-regulated kinase
ITIM-bearing molecules sum up
1. ITIM-bearing molecules seem to suppress cytokine responses
induced by other PRR through the recruitment of SHPs.
2. SHPs decrease the production of TLR-induced proinflammatory cytokines
3. but SHPs increase production of type 1 IFNs induced by TLRs
DCIR and MICL pathways plasticity
and interaction with TLR signaling are not clear.
Well, you already know, right? WORK MORE
SHP – SH2-domain containing protein tyrosin phosphatases
DCIR – DC immunoreceptor
MICL – myeloid C-type lectin like receptor
ITIM – immunoreceptor tyrosin-based inhibitory motif
TLR-independent signaling by CLRs. Dectin 1
1. Dectin 1 induces gene expression independently of other PRRs.
2. Works through recognition of β-1,3-glucan PAMPs that are expressed
by many pathogens (C.albicans, Aspergillus fumigatus, Pneumocystis carinii)
Dectin 1 – DC-associated C-type lectin 1
TLR-independent signaling by CLRs
2 x Dectin 1
(YxxL motifs, where x – any aa)
1
1
2
SYK (spleen tyrosine kinase)
2
3
3
?
?? TRAF2-TRAF6 (TNF
receptor-associated factors)
NF-kB (p65 and REL subunits)
4
4
Dectin 1
complex
CARD9
BCL-10
MALT1
“canonical NF-kB pathway”
Non-canonic NF-kB pathway
2 x Dectin 1
(YxxL motifs, where x – any aa)
1
SYK (spleen tyrosine kinase)
1
NIK (NF-kB-inducing kinase)
2
2
3
NF-kB
Dectin 1
IKKα (IkB kinase-α)
3
Never shown to SYK before.
Fast kinetics comparing
NF-kB
with other inductors
suggests that dectin 1
launches unique pathway
?
Dectin 1. Some more
1. SYK-CARD9-dependent pathway activated in response to C.albicans
leads to activation of NLR family, pyrin domain containing 3
(NLRP3=NALP3) inflammasome. The pathway leads to processing proIL-1β to active form IL-1β by caspase 1 through the generation of reactive
oxygen species. However, details are unclear and need clarification
2. SYK also converge with RAF1 pathway, as SYK induces phosphorylation
of p65 subunit of NF-kB by RAF1, which, finally, results in induction of il6,
il10, il12a and il12b genes transcription.
3. SYK- and RAF1-pathways fine-tune NF-kB-induced cytokine responses:
p65-P subunits form dimers that cannot bind to DNA. This leads to
reduced production of IL-1β, IL-12 and IL-23 – major cytokines for Th
differentiation.
4. Dectin 1 also induces CCL17 and CCL22 production (CC-chemokine
ligand) which are involved in the recruitment of other leukocytes.
Dectin 1 in the only CLR known to induce non-canonic NF-kB pathway!
Dectin 2 and mincle
Both molecules signal through ITAM-containing FcRγ (like BDCA2)
Dectin 2 / mincle
1
1
2
SYK (spleen tyrosine kinase)
?
2
CARD9-BCL10-MALT1
complex?
NF-kB
• CARD9 – caspase recruitment
domain family, member 9
• BCL10 – B-cell lymphoma 10
• MALT1 – Mucosa associated lymphoid
tissue lymphoma translocation gene 1
ITAM – immunoreceptor tyrosin-based activation motif
Dectin 2 and mincle
Dectin 2
+
• house dust mite allergens
Pro-inflam. cytokines:
TNF, IL-10
CXCL2
+
• C.albicans, Trichophyton rubrum,
Microsporum audouinii
neutrophils migrations
dead cells
Mincle in macrophages
+
CXCL2
pathogenic fungus Malassezia spp.
TNF
CLRs and T cell differentiation. C.albicans
1
1
2
DC-SIGN
1
2
3
+
Dectin 1
β-glucan structures on C.albicans
NF-kB
differentiation
Th1
3
+
+
Th17
CLRs and T cell differentiation. M.tuberculosis
1
DC-SIGN
1
2
2
3
+
Dectin 1
mannose on M.tuberculosis
NF-kB
differentiation
Th1
3
+
+
Th2
+
Th17
M.tuberculosis activation mechanisms
are not fully understood
Therapeutic potential of CLRs signaling
1. CLEC5A inhibition during dengue virus prevents virus-induced plasma
leakage and reduces mortality in mice.
2. Patients with SLE have reduced number of pDCs expressing BDCA2
that results in excessive production of type I IFNs, which is major
pathophysiological factor in SLE.
3. DCIR deficiency in mice leads to the development of autoimmune
diseases, such as rheumatoid arthritis.
4. Dectin 2 triggering by dust mite (Milben) allergens leads to cysteinyl
leukotriene production that causes inflammation.
5. Peanut allergen Ara h1 interacts with DC-SIGN and induces Th2-cells
responses.
• CLR agonists might activate pathways to prevent autoimmune disorders
• CLR antagonists could attenuate or modulate inflammation
Vaccination strategies
1. Specific delivery of antigens to DCs (e.g. on Ag-covered particles). This
approach was proved to work, but remains expensive and difficult.
2. Targeting DEC205, DC-SIGN or mannose receptor by antibodies induces
CD4+ and CD8+ cells responses. This can be used to induce tolerance to
pancreatic β-cells, thereby preventing type I diabetes (autoimmune type
mediated by T-cell destruction of β-cells). Therapy against β-cell antigens
expressed on DEC205 DCs reduces autoreactive CD8+ cells.
3. Mice immunization with zymosan or curdlan (dectin 1 ligands) induces
specific CD4+ Th1 and Th17, as well as CD8+ responses through SYKCRAD9 pathway. So could be used as adjuvants.
4. RAF1 inhibition is also studied, but RAF1 is involved in too many vital
mechanisms to be a proper immunomodulatory target.
5. Carbohydrate-expressing ligands lack specificity as are recognized by
several CLRs.
Vaccination strategies
DC-SIGN
1
1
2
2
3
+
+
Dectin 1
carbohydrate-coated particle with antigens
NF-kB
differentiation
Th1
+
Th2
+
Th17
4
3
4
4
Selective inhibition of RAF1 and/or SYK
allows the modulation of the immune responses
Future directions. Summary
1. CLRs are not just antigen uptakers, but modulators or even initiators of
immune responses.
2. Some of them can induce different signaling pathways by themselves.
3. Cross-talks between CLRs and TLRs signaling remains to be fully
understood (well, as everything in biology)
4. Many CLRs act either through SYK-CARD9 or RAF1 pathways and
activate NF-kB.
5. Role of other CLR-inducible transcription factors in immune system is still
unclear
Thank you for you attention