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Transcript
GBPs: Immunity to intracellular
pathogens
GBP
Juliana Ueda
Thais Herrero
Claudia Polli
IFN-γ : Central in host resistance to infection
WT
IFN KO
IFN-γ regulates the expression
of more than 1.200 genes
Mainly produced by:
Products:
Only a fraction:
Mediators of host immune responses
Remainder: little is known
GTPases
GTPases: GTP-binding proteins
NRAMP1: natural-resistance associated macrophage protein 1
Cellular functions of GTPases
Two conformations:
• Bound to GTP: active
Hydrolisis GTP
GDP and GMP
• Bound t GDP: inactive
GEF (guanine exchange factor)
GDP
GTP
Active GTPase
Cellular functions:
Activation of cell-surface receptors
to modulation of membrane-fusion events
Membrane tafficking
Cell signaling and migration
Translation and protein translocation
Nuclear transport
Families of GTPases
•
4 major families:
- Mx family (type I and II IFN
antiviral activity )
- Very large inducible GTPases (type II IFN
???)
- p47 immunity-related GTPases (IRGs) antimicrobial activity
- Guanylate-binding proteins (GBPs) ???
* Mice: IRGs against intracellular pathogens
Human: lack IRGs
GBPs
Type I IFN and IFN-γ
GBPs: Guanylate-binding proteins
7 hGBPs
11 mGBPs
GBPs: Guanylate-binding proteins
Induced by: type I IFN, IL-1β, LPS, IFN-γ
65-KDa
Isoprenylation:
Addition of either a C15 farnesyl or
C20 geranygeranyl lipid to the C-terminus
of the GBPs
leucine
serine
Isoprenylation is important in targeting proteins
to intracellular membranes and/or to facilitate
protein/protein interactions
GTP-binding domain(G domain)
GBPs are predominantly cytosolic and have,
at most, a relatively small portion of the total
amount associated with membranes.
Functions of GBPs
Regulation of vasculogenesis by proinflammatory cytokines
Mutant GTPase
active site
These are strinking phenomena
but seem unlike to constitute
the adaptative function of hGBP because
the G domain was not required
Functions of GBPs
Regulation of MMP1 production
MMP1: Matrix metalloprotease 1 is required for the breakdown of extracellular colagen, enabling
endothelial cells to form vessels in vivo
Functions of GBPs
Since GBPs are induced by both type I and type II IFNs,
it seemed logical to examine whether they are involved
in host defense
Functions of GBPs
Antiviral activity
HeLa cells
hGBP-1
SVS, EMCV m.o.i 1
mGBP-2
S52N: single point mutation GTP binding region
SVS, EMCV m.o.i 0.1
Functions of GBPs
Antiviral activity
The basis of antiviral effects is unknown.
The antiproliferative activity might help to limit the cell-to-cell spread of vírus.
Clone 1GBP-2
Clone 2 GBP-2
Control
SN52
Functions of GBPs
Response to Protozoan infections
MEFs
Functions of GBPs
Response to Bacterial infections
Functions of GBPs
Antibacterial activity
Thais
Claudia
NADPH oxidase
Neutrophil
http://www.clinsci.org
NADPH oxidase complex is a cluster of proteins that donate an electron from NADPH to molecular
oxygen (O2) to produce superoxide anion (O2-). This initiates the respiratory burst, a key step in immune
defense against bacterial and fungal pathogens
Also engulfed with the bacterium will be membrane proteins, including
gp91/p22 and FAD
Gp91phox large glycosylated protein
p22phoxsmaller adapter protein
FAD:cofactor
Soluble components:
p47phox
P67phox
p40phox
Electrons from NADPH are donated
to O2 to produce superoxide O2-
PKC-mediated phosphorylation p47phox
Translocation to the membrane
47phox binding to p22phox
Protons dissociated from NADPH
proton channels
interact with O2- to produce H2O2
Phagosome acidification
http://www.caymanchem.com
Second antimicrobial pathway…
Nonoxidative mechanisms:
http://www.fbs.osaka-u.ac.jp
Antioxid Redox Signal. 2009 August; 11(8): 1975–1988.
Microtubule-associated protein light-chain 3 (LC3)