gbps: immunity to intracellular pathogens juliana ueda thais herrero claudia polli gbp
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GBPs: Immunity to intracellular pathogens
Juliana UedaThais HerreroClaudia Polli
GBP
IFN-γ : Central in host resistance to infection
WT
IFN KO
IFN-γ regulates the expressionof more than 1.200 genes
Products:Only a fraction:Mediators of host immune responsesRemainder: little is known
Mainly produced by:
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: inactiveGEF (guanine exchange factor)GDP GTPActive GTPase
Cellular functions:Activation of cell-surface receptorsto modulation of membrane-fusion eventsMembrane taffickingCell signaling and migrationTranslation and protein translocationNuclear 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) ??? Type I IFN and IFN-γ
* Mice: IRGs against intracellular pathogens Human: lack IRGs GBPs
11 mGBPs
7 hGBPs
GBPs: Guanylate-binding proteins
GBPs: Guanylate-binding proteins
Induced by: type I IFN, IL-1β, LPS, IFN-γ65-KDa
GTP-binding domain(G domain)
Isoprenylation:Addition of either a C15 farnesyl orC20 geranygeranyl lipid to the C-terminus of the GBPs
Isoprenylation is important in targeting proteinsto intracellular membranes and/or to facilitate protein/protein interactions
GBPs are predominantly cytosolic and have,at most, a relatively small portion of the totalamount associated with membranes.
leucine
serine
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 cellshGBP-1SVS, EMCV m.o.i 1
mGBP-2S52N: single point mutation GTP binding regionSVS, 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.
Control
Clone 1GBP-2
Clone 2 GBP-2
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 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
Neutrophil
NADPH oxidase
http://www.clinsci.org
http://www.caymanchem.com
Gp91phox large glycosylated proteinp22phoxsmaller adapter proteinFAD:cofactor
Soluble components:p47phox
P67phox
p40phox
PKC-mediated phosphorylation p47phox
Translocation to the membrane47phox binding to p22phox
Electrons from NADPH are donated to O2 to produce superoxide O2
-
Protons dissociated from NADPH proton channels interact with O2
- to produce H2O2
Phagosome acidification
Also engulfed with the bacterium will be membrane proteins, including gp91/p22 and FAD
Second antimicrobial pathway…Nonoxidative mechanisms:
http://www.fbs.osaka-u.ac.jp
Microtubule-associated protein light-chain 3 (LC3)
Antioxid Redox Signal. 2009 August; 11(8): 1975–1988.