Please use this identifier to cite or link to this item: http://scholarbank.nus.edu.sg/handle/10635/19201
Title: CROSSTALK BETWEEN CRP AND FICOLINS REGULATES INNATE IMMUNITY
Authors: ZHANG JING
Keywords: C-reactive protein, ficolin, complement, GPCR43, signal transduction, conformational change
Issue Date: 12-Aug-2010
Source: ZHANG JING (2010-08-12). CROSSTALK BETWEEN CRP AND FICOLINS REGULATES INNATE IMMUNITY. ScholarBank@NUS Repository.
Abstract: Early detection and efficient removal of virulent pathogens are fundamental to host survival. Although C-reactive protein (CRP) and ficolins have long been known to independently initiate the classical and lectin complement pathways respectively under physiological condition, how they function under pathophysiological condition remains poorly understood. This thesis reports that a defined local ¿infection-inflammation condition¿ induced a 100-fold increase in the interaction between CRP and L-ficolin. This leads to communication between the classical and lectin pathways from which two amplification events emerged. Assays for C4 deposition, phagocytosis, and protein competition have consistently proven the functional significance of the amplification pathways in boosting the complement-mediated antimicrobial activity. This was again supported by the effective killing of P. aeruginosa in the plasma under defined local infection-inflammation condition, where powerful antimicrobial activity is provoked by CRP:L-ficolin interactions. Therefore, we conclude that the local infection-inflammation condition triggers a strong CRP:L-ficolin interaction, eliciting autonomous complement-amplification pathways which co-exist with and reinforce the classical and lectin pathways. Similar to L-ficolin, the M-ficolin was found to interact with CRP in a pH- and calcium-dependent manner. However, their biological consequences are divergent. We found that M-ficolin, overcomes its lack of membrane-anchor domain by docking constitutively onto a monocyte transmembrane receptor, GPCR43, to form a pathogen sensor-cum-signal transducer. On encountering microbial invaders, the M-ficolin:GPCR43 complex activates the NF-kB cascade to upregulate IL-8 production. We showed that mild acidosis occurring at the local site of infection triggers a strong interaction between the CRP and the M-ficolin:GPCR43 complex. This ternary complex curtails IL-8 production, thus, preventing immune over-activation. Our finding implies a possible mechanism which the host employs to expand its repertoire of immune function-cum-regulation tactics by promiscuous protein-protein networking. To understand the detailed mechanism of low pH- and low calcium- triggered CRP:M-ficolins interaction, we delineated the precise binding interface between M-ficolin and CRP. We found that the flexible C-terminus of the fibrinogen-like (FBG) domain of M-ficolin undergoes dramatic conformational change under acidosis and hypocalcaemia, which exposes unique motifs to augment its interaction with CRP. In silico analyses indicate that in contrast to normal condition, under infection-inflammation condition, the relocation of CRP binding site to the conserved pathogen sugar-ligand binding pocket and a simultaneous 100-fold increase in the affinity of M-ficolin:CRP complex might diverge the M-ficolin from pathogen recognition. This conformational change possibly helps to restore homeostasis. Therefore, infection-induced microenvironment perturbations act as a molecular switch to transform the FBG domain conformation and regulate its function. Overall, we have demonstrated that both the L- and M- ficolins interact with CRP to send the extracellular environmental cues into the cell to elicit intracellular immune response. This explains the intrinsic necessity to have two different ficolin isoforms, the L- and M- ficolins, each with high homology in our human body. Our findings provide new molecular insights into the host immune response to infection under infection-inflammation conditions. Our precise delineation of the interaction interface between CRP and M-ficolin will be useful for the future development of immunomodulators.
URI: http://scholarbank.nus.edu.sg/handle/10635/19201
Appears in Collections:Ph.D Theses (Open)

Show full item record
Files in This Item:
File Description SizeFormatAccess SettingsVersion 
Fig3.57_Mov3.MOV1.52 MBVideo Quicktime

OPEN

None Preview online
View/Download
Fig3.57_Mov4.MOV1.48 MBVideo Quicktime

OPEN

None Preview online
View/Download
Fig3.57_Mov5.MOV1.65 MBVideo Quicktime

OPEN

None Preview online
View/Download
Fig3.57_Legend.doc31.5 kBMicrosoft Word

OPEN

NoneView/Download
Fig3.57_Mov1.MOV1.56 MBVideo Quicktime

OPEN

None Preview online
View/Download
Fig3.57_Mov2.MOV1.55 MBVideo Quicktime

OPEN

None Preview online
View/Download
Legend_Fig3.14.doc4.93 kBMicrosoft Word

OPEN

NoneView/Download
Mov1Fig3.14.mov3.11 MBVideo Quicktime

OPEN

None Preview online
View/Download
Mov2Fig3.14.mov2.21 MBVideo Quicktime

OPEN

None Preview online
View/Download
Mov3Fig3.14.mov3.14 MBVideo Quicktime

OPEN

None Preview online
View/Download
Mov4Fig3.14.mov1.96 MBVideo Quicktime

OPEN

None Preview online
View/Download
Mov5Fig3.14.mov2.12 MBVideo Quicktime

OPEN

None Preview online
View/Download
Mov6Fig3.14.mov5.45 MBVideo Quicktime

OPEN

None Preview online
View/Download
01ZHANGJ.pdf6.91 MBAdobe PDF

OPEN

NoneView/Download
02ZHANGJ.pdf6.53 MBAdobe PDF

OPEN

NoneView/Download

Page view(s)

335
checked on Dec 11, 2017

Download(s)

128
checked on Dec 11, 2017

Google ScholarTM

Check


Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.