Signal Transduction Determines Cell Response

1
Signal Transduction Determines Cell Response
2
Immunological Synapse Formation between T and APC
Science 2002 2951539
3
Immunological Synapse
4
OUTLINE

1. Role of cytokines in immune system and
   hematopoiesis
2. Basic concepts of signal transduction
3. JAK-STAT pathway in cytokine signaling
4. Th1 and Th2 differentiation
5. Regulation of cytokine response
6. Negative regulators for cytokine signal
   transduction, SOCS and PIAS families

5
General Properties of Cytokines

1. Polypeptides
2. Produced in response to microbes and antigens
3. Mediate and regulate immune and inflammatory
   responses
4. Pleiotropic and redundant
5. Regulate the synthesis and actions of other
   cytokines
6. Actions are local or systemic (autocrine,
   paracrine, or endocrine)

6
Cytokines/Chemokines Involved in Innate Immunity
Modified from Cell. Mol. Immunol. Abbas
Lichtman 5th Ed. 2003
7
Cytokines/Chemokines Involved in Innate Immunity
Cytokine Producers TargetsEffects
TNFa IL-1 IL-12 IFNa/b IFNg Chemokine
MØ, DC, T cells Neutrophils activation
Endothelial cells activation
(inflammation) Hypothalamus
Fever Many cells apoptosis
MØ, endothelial Ditto
MØ, DC T cells NK IFNg
synthesis and CTL activity T
cells Th1 differentiation IFNa MØ
All cells antiviral state, increase MHC I
IFNb fibroblast NK cells activation NK,
NKT MØ activation (increased microbicidal) T
cells, CD8 B cells isotype switching to
IgG2A Many cells Increase MHC
I MHC II MØ, endothelial Leukocytes
chemotaxis, activation, Fibroblast, T cells
migration to tissues
Modified from Cell. Mol. Immunol. Abbas
Lichtman 5th Ed. 2003
8
How Adaptive Immunity Works
Modified from Cell. Mol. Immunol. Abbas
Lichtman 5th Ed.
9
Cytokines Involved in Adaptive Immunity
Cytokine Producers TargetsEffects
IL-2 IL-4 IL-5 Lymphotoxin IFNg
T cells T cells proliferation, cytokine
production B cells
proliferation, antibody production
NK proliferation and acitvation Th2 B
cells isotype switching to IgE T cells Th2
differentiation, proliferation
Th2 Eosinophils activation,
increase prod B cells
proliferation, IgA production T cells
Recruitment and activation of neutrophils
Th1, CD8 MØ activation (increased
microbicidal) NK, NKT B cells
isotype switching to IgG2A Many
cells Increase MHC I MHC II
Modified from Cell. Mol. Immunol. Abbas
Lichtman 5th Ed. 2003
10
Roles of Cytokines in Hematopoiesis
Cell. Mol. Immunol. 2003 Abbas Lichtman 5th ed.
11
What Happens When Ligands Bind to Receptors

• Conformational change of the receptors
• Opens ion channel
• Facilitates binding of intracellular signaling
  proteins such as chemokine receptor
• Dimerization (Oligomerization) of the receptors
• Bring signaling molecules into juxtaposition
• -induces post-translational modification
  such as phosphorylation in the receptors or
  signal meidators
• -activates downstream mediators

12
Phosphorylation of Proteins as a Controling
Mechanism for Signal Transduction

• Advantages
• Rapid does not require new protein synthesis or
  protein degradation
• Reversible easily reversed by action of protein
  phosphatases
• Easy to relay signals phosphorylation on Tyr,
  Thr, or Ser creating binding sites for other
  proteins

13
Tyrosine Phosphorylation Initiates Signaling(In
general)
PTK Protein Tyrosine Kinase PTP Protein
Tyrosine Phosphatase
Note Src-family kinase
14
Regulation of Activity of Src Family Kinase
Src family B cells Lyn, Fyn, Blk T cells
Lck, Fyn,
Immunobiology 6th ed. 2005, Janeway et al.
15
Major Events in Signal Transduction Mediated by
Receptor Tyrosine Kinase (RTK) or non-RTK

• Ligand-induced receptor dimerization
• Activation of kinases
• Activation of signal mediators
• Activation of transcription factors
• Translocation of transcription factors into
  nucleus and transactivation

16
Cytokine Receptor-mediated Signaling Pathways
17
Structural and Functional Domains of JAK Family
JAK family JAK1, JAK2, JAK3 and TYK2
Nat. Rev. Mol. Cell Biol. 2002 3651
18
Structural and Functional Domains of STATs
STAT family STAT1, STAT2, STAT3, STAT4,
STAT5A, STAT5B, and STAT6
Nat. Rev. Mol. Cell Biol. 2002 3651
19
Activation of JAKs and STATs by Cytokines
Ligand Jak kinases STATs
IFN family Type I IFN- IFNa or IFNb Tyk2,
Jak1 STAT1, STAT2 Type II IFN-IFNg Jak1,
Jak2 STAT1
gC family IL-2 Jak1, Jak3 STAT5 IL-4 Jak1,
Jak3 STAT5 IL-7 Jak1, Jak3 STAT5
gp130 family IL-6 Jak2 STAT3 IL-11 Jak2 STAT
3
Modified from Gene 2002 2851
20
Cytokine Receptor Families by Their Structures
21
Molecular Structure of Class I Receptors
One chain for Ligand Binding One chain for
Signal transducing
Cytokine Growth Factor Rev 2001 1219
22
Critical Roles of gC Family in Lymphocyte
Development and Function
Nat. Rev. Immunol.2001 1200
23
SCID Resulting from Defects in IL-7Ra, JAK3 or gc
Chain
N. Eng. J. Med. 2000 3431313
24
Phenotypes of JAK-Knockout Mice
Nat. Rev. Mol. Cell Biol. 2002 3651
25
Prevention of Organ Allograft Rejection by a
Specific Janus Kinase 3 Inhibitor
Science 2003 302875
26
Phenotypes of STAT Knockout Mice
Nat. Rev. Mol. Cell Biol. 2002 3651
27
Impaired Response to IFNa/b and Lethal Viral
Disease in Human STAT1 Deficiency
Nature Genet. 2003 33388 (U. Paris)
28
Properties of Chemokine and Chemokine Receptors

• Chemokines are classified (CC, CXC, CX3C, and XC)
  based on the number and sequential relationship
  of the first two of four conserved cysteines
• In general, CXC chemokines are critical for acute
  inflammation, CC chemokines are for chronic
  inflammation
• 50 chemokines 19 chemokine receptors ( human, as
  of 2006)
• Functional redundancy and promiscuity
• Interplay of the receptors and ligands can
  result in agonistic or antagonistic effect
• I-TACgt MIGgt IP10 (Th1 chemokines, via
  CXCR3) are antagonist for CCR3 by competing the
  binding of eotaxin to CCR3

29
G-Protein Coupled Receptor (GPCR)-mediated
Signaling Pathway
30
Trimeric GTP-binding Proteins (Large G protein)
Activation by 7-Transmembrane Receptor (7TM) or
GPCR
PLC
Ca
Nature Rev. Mol. Cell Biol. 2002 3639
31
Differentiation of Immature CD4 Helper T Cells
32
Figure 10-9
CD4 T-helper Cell Differentiation
33
Naïve CD4 T Cells can Differentiate into Two
Effector Cells
34
Development of Th1 and Th2 Subsets
Cell. Mol. Immunol. 5th ed. Abbas et al.
35
Effector Functions of Th1 Cells
Cell. Mol. Immunol. 5th ed. Abbas et al.
36
Effector Functions of Th2 Cells
Cell. Mol. Immunol. 5th ed. Abbas et al.
37
Differentiation of T-helper 1 Cells VS T-helper 2
Cells
Nat. Rev. Immunol. 2005 5125
38
Molecules Involved in Th Differentiation (I)
39
Molecules Involved in Th Differentiation (II)
40
Expanding the effector CD4 T-cell repertoire the
Th17 lineage
Current Opin. Immunol. 2006 18349
41

Negative Regulation of the JAK-STAT pathway

• Receptor-mediated endocytosis and degradation
• Dephosphorylation by tyrosine phosphatases
• Naturally occurring dominant negative STATs such
  as STAT1b and STAT3b that dont have
  transactivating domain
• Suppressor of cytokine signaling (SOCS) family
• Protein inhibitor of activated Stats (PIAS)

42
Cell 2002 109S121-S131
43
Negative Regulations of Cytokine Signaling
Nat. Rev. Immunity 2003 3900
44
Structural and Functional Domains of SOCS Family
K Kinase inhibitory region
Nat. Rev. Immunol. 2002 2410
45
Inhibitory Mechanisms of SOCS Molecules
Trend. Immunol. 2003 24659
46
(No Transcript)
47
SOCS1 Is a Critical Inhibitor of IFNg Signaling
and Prevents Fatal Neonatal Actions of this
Cytokine
Cell 1999 98597
48
Phenotypes of SOCS Knockout Mice
Nat. Rev. Mol. Cell Biol. 2002 3651
49
Hypersensitivity of SOCS-1 KO Mice to LPS In Vivo
Immunity 2002 Vol. 17583
50
SOCS1 Negatively Regulates TLR Signaling by
Mal/TIRAP Degradation
Forward
Nat. Immunol. 2006 7148
51
TLR Signaling Pathways
back
Cell Death Diff. 2006 13816
52
Structural and Functional Domains of PIAS Family
Nat. Rev. Immunol. 2005 5593
SAP Scaffold Attachment factor A and B, Acinus,
and PIAS RLD RING finger-like Zinc binding
domain AD Acidic domain SIM SUMO-
interacting motif S/T Serine and Threonine-rich
53
PIAS-protein Regions Involved in Proteinprotein
Interactions
Nat. Rev. Immunol. 2005 5593
54
Proposed Mechanisms for Inhibiting the JAKSTAT
Pathway by PIAS Proteins
Nat. Rev. Immunity 2003 3900
55
Some but not All IFNa-inducible Genes Are
Enhanced in Pias1-/- MEF
Nat. Immunol. 2004 5891
56
Enhanced Antiviral Response and Sensitivity to
LPS-induced Toxic Shock in Pias1-/- Mice
Nat. Immunol. 2004 5891
57
PIAS1 Affects only Subset of IFN-inducible Genes
(Promoter with Weaker STAT-binding Sites)
Nat. Immunol. 2004 5875
58
Enhanced Expression of NF- kB-Regulated Genes in
Response to TNF-a and LPS in Pias1 null Cells
Mol. Cell. Biol. 2005, 251113
59
Specificity of PIAS1-mediated Transcriptional
Repression in STAT1 and NF-kB Signaling
Nat. Rev. Immunol. 2005 5593
60

• Suggested
  Readings
• JAK-STAT pathways and transcriptional activation
  in response to IFNs and other extracellular
  signaling proteins Science 1994 2641415
• 2. STAT transcriptional control and biologic
  impact.
• Nat. Rev. Mol. Cell Biol. 2002 3651
• 3. Regulation of gene-activation pathways by
  PIAS proteins in the immune system
• Nat. Rev. Immunol. 2005 5593
• Textbooks
• Immunobiology Janeway 6th ed. 2005, Chapter 6, 9
  by Janeway
• Cellular and Molecular Immunology 5th ed. 2003
  Chaper 13 by Abbas and Lichtman