Role of NF-?B in the Regulation of Immunity and Apoptosis - PowerPoint PPT Presentation

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Role of NF-?B in the Regulation of Immunity and Apoptosis

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Title: Role of NF-?B in the Regulation of Immunity and Apoptosis


1
Role of NF-?B in the Regulation of Immunity and
Apoptosis
  • Kavitha Bharatham

2
Abstract
  • Introduction
  • Structural Description
  • Role as regulator of Immune responses
  • Role as regulator of apoptosis
  • Regulation Mechanism
  • As target for Therapy
  • Conclusions

3
Introduction
4
Nuclear Factor kappa B (NF- ?B)
  • Multifunctional transcription factor
  • Play central role in the cellular response to a
    variety of stress signal by regulating genes
  • Exists as homo or hetero-dimers found inactive in
    the cytoplasm
  • Upon stimulation, active NF-kB rapidly
    translocates to the nucleus where it binds
    ?B-sites and activates target genes

5
Role of NF- ?B/Rel family
  • Involved in proinflammatory response a first
    line of defense against infectious diseases and
    cellular stress
  • Signal ??Activated NF- ?B ? immune defence
    activated
  • Immune response, inflammatory response, accute
    phase response
  • NF-?B also a major anti-apoptopic factor
  • aberrant activation of NF- ?B causes
  • Inflammatory diseases, Rheumatoid arthritis,
  • Asthma, Atherosclerosis, Alzheimer
  • helps keeping cancer cells alive
  • NF-?B also promoting growth
  • Activated NF- ?B ? cyclin D expression enhanced ?
    growth

6
Factors that induce NF-kB
Reactive Oxygen Species (ROS)
Leukemia 161053-1068, 2002
7
Genes Regulated by NF-kB
Nat.Rev.Cancer 2301-310, 2002
8
Disorders associated with aberrant NF-kB
activation
  • Rheumatoid arthritis
  • Atherosclerosis
  • Vascular dysfunction
  • Multiple sclerosis
  • Neurodegenerative disorders
  • Inflammatory bowel disease
  • H. pylori-associated gastritis
  • Systemic inflammatory response syndrome
  • And the list is growing
  • Autoimmune thyroid disease
  • Cystic fibrosis
  • Diabetes
  • Aging
  • Macular degeneration
  • HIV/AIDS
  • Cancer
  • Septic shock

9
Structural Description
10
The NF- ?B/Rel family
  • NF-?B belongs to the Rel family, which contains
    five mammalian Rel/NF- ?B proteins
  • Potent transactivators synthesized in their
    mature form
  • RelA (p65)
  • c-Rel
  • RelB
  • Synthesized as precursors that are post
    translationally processed with no transactivation
    properties
  • NF- ?B1 (p105 undergoes proteolytic maturation to
    p50)
  • NF- ?B2 (p100 undergoes proteolytic maturation to
    p52)
  • RelB forms dimer only with p50/p52
  • Most Common form p50/p65 (NF-kB1/RelA)

11
NF- ?B proteins structure
12
Structural Details
  • Rel Homology Domain (RHD) 300aa conserved domain
    of Rel family which contains NLS (Nuclear
    localisation sequence) with several functions
  • DNA-binding (N-terminal half)
  • Dimerization (C-terminal half)
  • I?B-interaction (C-terminal half)
  • I?B (Inhibitor of Nf- ?B) blocks NLS and abolish
    translocation to nucleus
  • IkB family includes I?B-?, I?B-?, I?B-??and
    I?B-?, Bcl-3, etc.,
  • They posess ankyrin-repeats which are necessary
    for RHD-interaction
  • impedes DNA-binding
  • Upon Signal undergoes dissociation and degradation

13
Dimerization
Dimer formation is necessary for
DNA-binding Each subunit interacts with one half
site kB-sites are symmetric 5-GGGRNNYYCC-3
p50
p50
RelA
RelA
p50
14
Structure NFkB (p50-p65) DNA
Side view
b
  • --5-GGGRNNYYCC-3--
  • - 3-CCCYNNRRGG-5--

15
Role as Regulator of Immune responses
16
Role in inflammation
TNF-alpha
  • Inflammation is a process by which the body
    attempts to dilute, destroy, or isolate a noxious
    (harmful) agent and repair damage

Transcription
TNF? Il-1? Up regulation of adhesion molecules
(ICAM-1, VCAM-1) Cytokines that further enhance
the immune response activators of inflammatory
pathways (arachidonic acid metabolites,
superoxides and nitric oxide)
17
Role of IKK in Activating NF-?B
Pro-inflamatory cytokines, Pathogen associated
molecular patterns (PAMPs), TNF Receptor (TNFR),
Toll-like Receptor (TLR), Interleukin-1 receptor
(IL-1R)
Two types of inactive complexes in the
cytoplasm Trimers RHD-Homo-or heterodimers
bound to an IkB-repressor Heterodimers
Rel-protein unprocessed RHD-precursor (p105,
p110)
Transcription
NLS is exposed and translocated to Nucleus
kB site
18
Two main signaling pathways
Innate
Adaptive
Inflammatory/Immune Proteins
NUCLEUS
mRNA
Target genes
Transcription
19
Innate vs Adaptive NF-kB activation pathway
NonCanonical/NonClassical/Adaptive NF-kB
activation pathway Affects NF-kB2, which
preferentially dimerizes with RELB Triggered by
members of the tumor- necrosis factor (TNF)
cytokine family Depends selectively on
activation of the IKKa subunit another kinase
NIK. Induce the phosphorylation-dependent
proteolytic removal of the IkB-like C-terminal
domain of NF-kB2
Canonical/Classical/Innate NF-kB activation
pathway Applies to RelA-p50 and
c-Rel-p50 Retained in cytoplasm by IkB Triggered
by microbial and viral infections and exposure
to proinflammatory cytokines Depends mainly on
the IKKb subunit of the IKK complex. Induce the
phosphorylation-dependent proteolytic removal of
the IkB
20
Role as Regulator of Apoptosis
21
Apoptosis is Programmed Cell Death
Apoptosis is needed to destroy cells that
represent a threat to the integrity of the
organism
  • Inducers
  • Damage-related inducers
  • heat shock, viral infection, bacterial toxins,
    oncogenes (myc, rel, E1A), tumor suppressors
    (p53), cytolytic T cells, oxidants
  • Therapy-associated agents
  • Chemotherapeutic drugs (e.g., cispatin, nitrogen
    mustard)
  • Antracyclines (doxorubicin), gamma radiation, UV
    radiation
  • Toxins
  • Ethanol, b-amyloid peptide

22
Diseases Associated with Deregulated Apoptosis
Increased Apoptosis
Inhibition of Apoptosis
Cancer Follicular lymphomas carinomas with p53
mutations hormone dependent tumours breast
cancer, prostate cancer, ovarian
cancer Autoimmune Disorders Systemic lupus
erythematosus Immune-mediated
glomerulonephritus Viral Infections
Herpesvirus, poxvirus, adenovirus
AIDS Neurodegernative disorders Alzeheimers
disease, Parkinsons disease, Amyotrophic
lateral sclerosis Retinitis pigmentosa Myelodysp
lastic syndromes Aplastic anaemia Ischaemic
Injury Myocardial infarction, Stroke,
Reperfusion injury Toxin-Induced liver disease
Alcohol
23
NF-kB is an anti-apoptotic factor
Via NF-kB TNF blocks its own cell death
potential
Chemotherapy activates NF-kB within tumor cells
NF-kB inhibitors augment chemotherapy
24
Mechanism behind Anti-apoptotic activity
RIP Receptor interacting protein FADD Fas
associated Death domain IAP Inhibitor of
Apoptosis TRAF TNFR associated protein Bid
Bcl-2 interacting domain JNK Jun N-terminal
kinase
25
Balance between life and death
When NF-kB is not inhibited
When NF-kB is inhibited
PRO-APOPTOTIC PROTEINS
ANTI-APOPTOTIC PROTEINS
26
Regulation Mechanism
27
Negative feedback Attenuation of NF-kB response
  • Negative loop IkB is under direct control of
    NF-kB

IkB
IkB
ikb
kB site
  • RIP and TRAF1 are cleaved

Caspase 8
RIP
Cleaved
TRAF1
28
Therapeutic inhibition of NFkB
29
Conclusions
  • The NF-kB is an important pathway in regulating
    the stress response in the body
  • It plays a key role in oncogenesis
  • Work continues on manipulating the pathway for
    use in therapy
  • Complete elucidation of the mechanisms involved
    in regulation of NF-kB activation is required to
    generate inhibitors
  • Therapeutic inhibitors that selectively block
    NF-kB activation in cancer cells without
    effecting normal functions are required

30
References
  • Seminars in Cancer Biology 13 (2003) 107114
  • TRENDS in Immunology Vol.25 No.6 June 2004
  • Clinical Chemistry 451 717 (1999)
  • The Journal of Clinical Investigation January
    2001 Volume 107 Number 2
  • Human Molecular Genetics, 2002, Vol. 11, No. 20
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