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John G Raynes

Publications and source records attributed to John G Raynes.

12 recordsLinked to original sources
PubMed2007

The lipidation status of acute-phase protein serum amyloid A determines cholesterol mobilization via scavenger receptor class B, type I.

During the acute-phase reaction, SAA (serum amyloid A) replaces apoA-I (apolipoprotein A-I) as the major HDL (high-density lipoprotein)-associated apolipoprotein. A remarkable portion of SAA exists in a lipid-free/lipid-poor form and promotes ABCA1 (ATP-binding cassette transporter A1)-dependent cellular cholesterol efflux. In contrast with lipid-free apoA-I and apoE, lipid-free SAA was recently reported to mobilize SR-BI (scavenger receptor class B, type I)-dependent cellular cholesterol efflux [Van der Westhuyzen, Cai, de Beer and de Beer (2005) J. Biol. Chem. 280, 35890-35895]. This unique property could strongly affect cellular cholesterol mobilization during inflammation. However, in the present study, we show that overexpression of SR-BI in HEK-293 cells (human embryonic kidney cells) (devoid of ABCA1) failed to mobilize cholesterol to lipid-free or lipid-poor SAA. Only reconstituted vesicles containing phospholipids and SAA promoted SR-BI-mediated cholesterol efflux. Cholesterol efflux from HEK-293 and HEK-293[SR-BI] cells to lipid-free and lipid-poor SAA was minimal, while efficient efflux was observed from fibroblasts and CHO cells (Chinese-hamster ovary cells) both expressing functional ABCA1. Overexpression of SR-BI in CHO cells strongly attenuated cholesterol efflux to lipid-free SAA even in the presence of an SR-BI-blocking IgG. This implies that SR-BI attenuates ABCA1-mediated cholesterol efflux in a way that is not dependent on SR-BI-mediated re-uptake of cholesterol. The present in vitro experiments demonstrate that the lipidation status of SAA is a critical factor governing cholesterol acceptor properties of this amphipathic apolipoprotein. In addition, we demonstrate that SAA mediates cellular cholesterol efflux via the ABCA1 and/or SR-BI pathway in a similar way to apoA-I.

ATP Binding Cassette Transporter 1↗
PubMed2006

Serum amyloid A is an innate immune opsonin for Gram-negative bacteria.

Serum amyloid A (SAA) is the major acute-phase protein in man and most mammals. Recently we demonstrated that SAA binds to many Gram-negative bacteria including Escherichia coli and Pseudomonas aeruginosa through outer membrane protein A (OmpA) family members. Therefore we investigated whether SAA altered the response of innate phagocytic cells to bacteria. Both the percentage of neutrophils containing E coli and the number of bacteria per neutrophil were greatly increased by SAA opsonization, equivalent to the increase seen for serum opsonization. In contrast, no change was seen for Streptococcus pneumoniae, a bacteria that did not bind SAA. Neutrophil reactive oxygen intermediate production in response to bacteria was also increased by opsonization with SAA. SAA opsonization also increased phagocytosis of E coli by peripheral blood mononuclear cell-derived macrophages. These macrophages showed strong enhancement of TNF-alpha and IL-10 production in response to SAA-opsonized E coli and P aeruginosa. SAA did not enhance responses in the presence of bacteria to which it did not bind. These effects of SAA occur at normal concentrations consistent with SAA binding properties and a role in innate recognition. SAA therefore represents a novel innate recognition protein for Gram-negative bacteria.

Gram-Negative Bacteria↗
PubMed2005

CD11b regulates recruitment of alveolar macrophages but not pulmonary dendritic cells after pneumococcal challenge.

Despite their close physical and functional relationships, alveolar macrophages (AMs) and pulmonary dendritic cells (pulDCs) have rarely been examined together in the context of infection. Using a nonlethal, resolving model of pneumonia caused by intranasal injection of Streptococcus pneumoniae, we demonstrate that AMs and pulDCs exhibit distinct characteristics during pulmonary inflammation. Recruitment of AMs and pulDCs occurred with different kinetics, and increased numbers of AMs resulted mainly from the appearance of a distinct subset of CD11b(High) AMs. Increased numbers of CD11b(High) and CD11b(Low) AMs, but not pulDCs, were recoverable from bronchoalveolar lavage fluid. CD11b expression on AMs was significantly increased by granulocyte-macrophage colony-stimulating factor but not by interleukin-10 or pathogen-associated stimuli. Finally, antibody blockade demonstrated that CD11b was critical for the recruitment of AMs, but not pulDCs, into the lung after pneumococcal challenge. These data demonstrate that there are significant differences between AM and pulDC responses to inflammatory pathogenic stimuli in vivo.

Animals↗
PubMed2005

The role played by tumor necrosis factor during localized and systemic infection with Streptococcus pneumoniae.

Tumor necrosis factor (TNF) has been proposed as a major mediator of host resistance in murine models of Streptococcus pneumoniae infection; in humans, anti-TNF therapies have been implicated in increased susceptibility to pneumococcal infection. Here, we use nonlethal (serotype 6B) and lethal (serotype 3) S. pneumoniae, neutralizing monoclonal antibodies to TNF, and TNF gene-deficient mice to reexamine the role played by TNF in antistreptococcal responses. After nonlethal challenge, primary resistance and all examined parameters of the cellular inflammatory response occurred independently of TNF activity. After lethal challenge, TNF deficiency resulted in more-rapid death but did not affect lung inflammation. However, the livers of the TNF gene-deficient mice, but not of the control mice, exhibited extensive signs of systemic disease. TNF, therefore, is dispensable for a complete cellular pulmonary inflammatory response to S. pneumoniae infection but enhances survival from disseminated lethal infection, at least in part by delaying systemic organ damage.

Animals↗
PubMed2005

Serum amyloid A protein binds to outer membrane protein A of gram-negative bacteria.

Serum amyloid A (SAA) is the major acute phase protein in man and most mammals. We observed SAA binding to a surprisingly large number of Gram-negative bacteria, including Escherichia coli, Salmonella typhimurium, Shigella flexneri, Klebsiella pneumoniae, Vibrio cholerae, and Pseudomonas aeruginosa. The binding was found to be high affinity and rapid. Importantly, this binding was not inhibited by high density lipoprotein with which SAA is normally complexed in serum. Binding was also observed when bacteria were offered serum containing SAA. Ligand blots following SDS-PAGE or two-dimensional gels revealed two major ligands of 29 and 35 kDa that bound SAA when probing with radiolabeled SAA or SAA and monoclonal anti-SAA. Following fractionation the ligand was found in the outer membrane fraction of E. coli and was identified by matrix-assisted laser desorption ionization time-of-flight mass spectrometry to be outer membrane protein A (OmpA). OmpA-deficient E. coli did not bind SAA, and following purification of OmpA the protein retained binding activity. The ligands on other bacteria were likely to be homologues of OmpA because wild type, but not OprF-deficient, P. aeruginosa bound SAA.

Bacterial Outer Membrane Proteins↗
PubMed2004

FcgammaRIIa expression with FcgammaRI results in C-reactive protein- and IgG-mediated phagocytosis.

C-reactive protein (CRP) is a pattern-recognition molecule, which can bind to phosphorylcholine and certain phosphorylated carbohydrates found on the surface of a number of microorganisms. CRP has been shown recently to bind human Fc receptor for immunoglobulin G (IgG; FcgammaR)I and mediate phagocytosis and signaling through the gamma-chain. To date, binding of monomeric CRP to FcgammaRII has been contentious. We demonstrate that erythrocytes opsonized with CRP bind FcgammaRIIa-transfected COS-7 cells. In addition, we demonstrate that FcgammaRI can use FcgammaRIIa R131 and H131 to phagocytose erythrocytes coated with IgG or purified or recombinant CRP in the absence of the gamma-chain. COS-7 cells expressing FcgammaRIIa or FcgammaRI alone did not phagocytose opsonized erythrocytes. Such phagocytosis required the cytoplasmic domain of FcgammaRIIa, as mutation of tyrosine at position 205 and truncation of the cytoplasmic domain from the end of the transmembrane region (position 206), resulting in the loss of the immunoreceptor tyrosine activatory motif, abrogated phagocytosis. FcgammaRIIa R131 was more efficient than FcgammaRIIa H131 at mediating CRP-dependent phagocytosis.

Animals↗
PubMed2004

De-novo design of complementary (antisense) peptide mini-receptor inhibitor of interleukin 18 (IL-18).

Complementary (antisense) peptide mini-receptor inhibitors are complementary peptides designed to be receptor-surrogates that act by binding to selected surface features of biologically important proteins thereby inhibiting protein-cognate receptor interactions and subsequent biological effects. Previously, we described a complementary peptide mini-receptor inhibitor of interleukin-1beta (IL-1beta) that was designed to bind to an external surface loop (beta-bulge) of IL-1beta (Boraschi loop) clearly identified in the X-ray crystal structure of this cytokine. Here, we report the de-novo design and rational development of a complementary peptide mini-receptor inhibitor of cytokine interleukin-18 (IL-18), a protein for which there is no known X-ray crystal structure. Using sequence homology comparisons with IL-1beta, putative IL-18 surface loops are identified and used as a starting point for design, including a loop region 1 thought to be equivalent with the Boraschi loop of IL-1beta. Only loop region 1 complementary peptides are found to be promising leads as mini-receptor inhibitors of IL-18 but these are prevented from being properly successful owing to solubility problems. The application of "M-I pair mutagenesis" and inclusion of a C-terminal arginine residue are then sufficient to solve this problem and convert one lead peptide into a functional complementary peptide mini-receptor inhibitor of IL-18. This suggests that the biophysical and biological properties of complementary peptides can be improved in a rational and logical manner where appropriate, further strengthening the potential importance of complementary peptides as inhibitors of protein-protein interactions, even when X-ray crystal structural information is not readily available.

Drug Design↗
PubMed2002

Specific interactions between sense and complementary peptides: the basis for the proteomic code.

The discovery of the genetic code was one of the milestone events in biology: a conserved, universal code defining the primary amino acid sequences of all proteins of all organisms. However, this code has been thought to be limited, unable to provide additional information appropriate to defining the three-dimensional structure and function of these proteins. This raises important questions. Can there be more to the genetic code? Is there a code embedded within the code? Does a two-dimensional genetic code exist? In our view, the answer to all three of these questions is a qualified "yes". This review describes how sense and complementary peptides coded for by mutually complementary nucleic acid sequences are capable of interacting specifically, thereby suggesting the existence of a second, two-dimensional genetic code (proteomic code). Theories attempting to explain such specific interactions between sense and complementary peptides are discussed including the Mekler-Idlis (M-I) pair theory that suggests that each codon-directed amino acid residue in a sense peptide may make a specific pair-wise interaction with the corresponding complementary codon-directed residue in the complementary peptide. In effect, through-space interactions between pairs of amino acid residues are suggested as being specified by the genetic code and its complement. The biological implications of sense/complementary peptide interactions are potentially vast but still to be fully understood and appreciated. That such peptide/peptide interactions could provide the basis for understanding and constructing the proteomic code remains to be properly established but research to date suggests that we should be able to make a start in that direction.

Amino Acids↗
PubMed2002

C-reactive protein-mediated phagocytosis and phospholipase D signalling through the high-affinity receptor for immunoglobulin G (FcgammaRI).

C-reactive protein (CRP) is the prototypic acute-phase protein in man which performs innate immune functions. CRP-mediated phagocytosis may be indirect, through activation of complement and complement receptors, or direct, through receptors for the Fc portion of immunoglobulin G (IgG; FcgammaRs) or even a putative CRP-specific receptor. No strong evidence has been shown to indicate which receptors may be responsible for phagocytosis or signalling responses. Using BIAcore technology, we confirm that CRP binds directly to the extracellular portion of FcgammaRI with a threefold higher affinity than IgG (KD = 0.81 x 10-9 m). Binding is Ca2+ dependent and is inhibited by IgG1 but not by phosphorylcholine (PC). CRP opsonization (using CRP concentrations within the normal human serum range) of PC-conjugated sheep erythrocytes increased phagocytosis of these particles by COS-7 cells transfected with FcgammaRI-II chimaera or FcgammaRI/gamma-chain. Interferon-gamma-treated U937 cells, which signal through FcgammaRI to activate phospholipase D (PLD) in response to cross-linked IgG, were also activated by CRP without any requirement for further cross-linking. These studies indicate that CRP is capable of binding to and cross-linking FcgammaRI thereby resulting in PLD activation and increased phagocytosis. Uptake by FcgammaRI has been reported to promote various acquired immune responses suggesting that CRP could act in a similar way.

Animals↗
PubMed2002

Activation of p38 mitogen-activated protein kinase attenuates Leishmania donovani infection in macrophages.

Leishmania-induced macrophage dysfunctions have been correlated with altered signaling events. In this work, we report that SB203580, a specific inhibitor of p38 mitogen-activated protein kinases (MAPK), increases Leishmania donovani survival in human peripheral blood mononuclear macrophages. Consistent with this finding, activation of p38 and c-jun N-terminal kinase (JNK) MAPK signaling pathways by anisomycin significantly reduced parasite survival within these cells. However, the majority of the effect was seen in a 50% reduction in the percentage of macrophages infected, with little effect on the highly infected macrophages. The observed effect was likely to be due to the p38 MAPK pathway since SB203580 was able to completely reverse the effect of anisomycin. These findings suggest that the previously reported p38 MAPK inhibition by Leishmania infection may be partially overcome by anisomycin. Similar effects were observed in pretreated macrophages or in treatment of infected macrophages. These results suggests that p38 MAPK activation may have a potential therapeutic value in the treatment of visceral leishmaniasis.

Animals↗
PubMedDate not supplied

C-reactive protein-mediated phagocytosis of Leishmania donovani promastigotes does not alter parasite survival or macrophage responses.

C-reactive protein (CRP) is an acute phase protein that binds to surface structures of a number of different organisms. Leishmania donovani express CRP ligand when first entering the mammalian host and CRP has been shown to alter macrophage function. The aim of this study was to investigate the functional significance of CRP-mediated uptake of L. donovani on survival of the parasite within human macrophages and macrophage cell responses to the infection. CRP opsonized L. donovani uptake was inhibitable by including excess CRP in the fluid phase, suggesting Fc receptor usage rather than indirect complement-mediated uptake. Comparing equivalent initial infection loads, parasite survival over 72 h within peripheral blood derived macrophages (PBMs) and differentiated U937 cells was unaltered by CRP. Whereas CRP increased macrophage responses to phosphorylcholine coated erythrocytes, no significant alteration in tumour necrosis factor-alpha, interleukin (IL)-10 or IL-12 production from PBMs was observed between CRP opsonized or unopsonized L. donovani promastigotes. Thus, in contrast to other systems, where CRP opsonization results in macrophage activation, Leishmania can use CRP to improve infection without inducing detrimental macrophage activation.

Animals↗