Peptidoglycan Recognition Protein 1 Research Articles

Regional and age dependent changes in gene expression of Toll-like receptors and key antimicrobial defence molecules throughout the gastrointestinal tract of dairy calves

The primary aim of this study was to determine regional and age-dependent expression patterns of Toll-like receptors (TLRs), peptidoglycan recognition protein 1 (PGLYRP1), and β-defensin in rumen, jejunum, ileum, cecum and colon of 3week (n=8) and 6month old (n=8) calves. The expression of most TLRs was significantly down-regulated throughout the gastrointestinal tract (GIT) with increasing age. TLR10 expression was significantly higher in ileum than all other gut regions, irrespective of age. TLR2 and TLR4 expression were significantly higher in the cecum and colon of 6month old calves. Furthermore, expression of β-defensin, and PGLYRP1 was only detectable in 6month old calves. The expression of TLRs was positively or negatively correlated with population of total bacteria and/or lactic acid bacteria depending on the GIT region. These observations indicate that innate immune responses to commensal microflora may vary significantly throughout the GIT and with age changes.

Involvement of Manduca sexta peptidoglycan recognition protein-1 in the recognition of bacteria and activation of prophenoloxidase system

Although the importance of peptidoglycan recognition proteins (PGRPs) in detecting bacteria and promoting immunity is well recognized in Drosophila melanogaster and other insect species, such a role has not yet been experimentally established for PGRPs in the tobacco hornworm, Manduca sexta. In this study, we purified M. sexta PGRP1 from the baculovirus-insect cell expression system, tested its association with peptidoglycans and intact bacteria, and explored its possible link with the prophenoloxidase activation system in larval hemolymph. Sequence comparison suggested that PGRP1 is not an amidase and lacks residues for interacting with the carboxyl group of meso-diaminopimelic acid-peptidoglycans (DAP-PGs). M. sexta PGRP1 gene was constitutively expressed at a low level in fat body, and the mRNA concentration became much higher after an injection of Escherichia coli. Consistently, the protein concentration in larval plasma increased in a time-dependent manner after the immune challenge. Purified recombinant PGRP1 specifically bound to soluble DAP-PG of E. coli but not to soluble Lys-type PG of Staphylococcus aureus. In addition, this recognition protein completely bound to insoluble PGs from Micrococcus luteus, Bacillus megaterium and Bacillus subtilis, whereas its association with the bacterial cells was low even though their peptidoglycans are exposed on the cell surface. After PGRP1 had been added to plasma of naïve larvae in the absence of microbial elicitor, there was a concentration-dependent increase in prophenoloxidase activation. Phenoloxidase activity, as usual, increased after the plasma was incubated with peptidoglyans or bacterial cells. These increases became more prominent when insoluble M. luteus or B. megaterium PG or soluble E. coli PG and PGRP1 were both present. Statistic analysis suggested a synergistic effect caused by interaction between PGRP1 and these PGs. Taken together, these results indicated that PGRP1 is a member of the M. sexta prophenoloxidase activation system, which recognizes peptidoglycans from certain bacteria and initiates the host defense response. The unexplained difference between the purified PGs and intact bacteria clearly reflects our general lack of understanding of PGRP1-mediated recognition and how it leads to proPO activation.

Diversity and evolution of 11 innate immune genes in Bos taurus taurus and Bos taurus indicus cattle

The Toll-like receptor (TLR) and peptidoglycan recognition protein 1 (PGLYRP1) genes play key roles in the innate immune systems of mammals. While the TLRs recognize a variety of invading pathogens and induce innate immune responses, PGLYRP1 is directly microbicidal. We used custom allele-specific assays to genotype and validate 220 diallelic variants, including 54 nonsynonymous SNPs in 11 bovine innate immune genes (TLR1-TLR10, PGLYRP1) for 37 cattle breeds. Bayesian haplotype reconstructions and median joining networks revealed haplotype sharing between Bos taurus taurus and Bos taurus indicus breeds at every locus, and we were unable to differentiate between the specialized B. t. taurus beef and dairy breeds, despite an average polymorphism density of one locus per 219 bp. Ninety-nine tagSNPs and one tag insertion-deletion polymorphism were sufficient to predict 100% of the variation at all 11 innate immune loci in both subspecies and their hybrids, whereas 58 tagSNPs captured 100% of the variation at 172 loci in B. t. taurus. PolyPhen and SIFT analyses of nonsynonymous SNPs encoding amino acid replacements indicated that the majority of these substitutions were benign, but up to 31% were expected to potentially impact protein function. Several diversity-based tests provided support for strong purifying selection acting on TLR10 in B. t. taurus cattle. These results will broadly impact efforts related to bovine translational genomics.

Abstract 4990: Multi-Marker Approach Using Novel Biomarkers Improves Prediction of Subclinical Atherosclerosis: Observations from the Dallas Heart Study

Background: Although many novel markers are independently associated with cardiovascular risk, few significantly improve predictive performance. We hypothesized that combining multiple novel biomarkers would improve prediction of subclinical atherosclerosis over standard methods. Methods: We measured coronary calcium (CAC) by electron beam CT (n=2440), as well as hsCRP, NT-proBNP, and four novel biomarkers including soluble receptor for advanced glycation end products (sRAGE), peptidoglycan recognition protein-1 (PGLYRP-1), soluble endothelial cell-selective adhesion molecule (sESAM), and osteoprotegerin (OPG) in the Dallas Heart Study, a multi-ethnic probability-based population sample age 30 – 65. An integer score was created based on the number of biomarkers that were elevated >= 95th percentile for sex and race. The incremental value of the biomarker score over a model including Framingham risk categories in predicting CAC was analyzed. Results: Increasing biomarker score was associated with increased CAC prevalence (59% for score >= 3 vs. 17% for score = 0, figure ). Compared with the Framingham risk model alone, the addition of the biomarker score significantly increased the C index (0.705 vs. 0.749, p<0.0001), lowered the Bayesian Information Criterion (2232 vs. 2195), and also improved reclassification into higher and lower risk categories (Net Reclassification Index = 14.2%, p<0.0001; Integrated Discrimination Index =2.4%, p<0.0001). Conclusion: Use of a multi-marker score including established and novel biomarkers improves prediction of CAC beyond the Framingham risk categories using multiple different statistical metrics. Figure. Prevalence of CAC by Biomarker Score*

Analysis of sequence variability and protein domain architectures for bovine peptidoglycan recognition protein 1 and Toll-like receptors 2 and 6

The mammalian Toll-like receptors (TLRs) recognize invading pathogens, thereafter provoking innate immune responses, whereas peptidoglycan recognition protein 1 (PGLYRP1) is directly microbicidal. The primary objective of this study was to characterize single-nucleotide polymorphisms (SNPs) and insertion-deletion polymorphisms (indels) within bovine TLR2, TLR6, and PGLYRP1, thereby facilitating future TLR signaling, association, and PGLYRP1 microbicidal assays relevant to bovine innate immunity. Comparative sequence analysis for 10 bovine breeds revealed 83 polymorphisms (82 SNPs, 1 indel), with 15 nonsynonymous SNPs located within predicted functional domains. Of the 83 polymorphisms detected, 72 (87%) are reported here for the first time. Several predicted amino acid replacements encoded by bovine TLR2 and TLR6, but not PGLYRP1, resulted in the confident prediction of protein domain alterations. Prediction and comparison of protein domain architectures for TLR2 and TLR6 revealed six regions of leucine-rich-repeat patterning that was conserved among multiple species. Collectively, differences in the patterns and frequencies of polymorphism were noted between bovine TLRs that predominantly recognize viral ligands (TLRs 3, 7, 8, 9) and those that recognize microbial and/or unknown ligands (TLRs 1, 2, 5, 6, 10).

The association between peptidoglycan recognition protein-1 and coronary and peripheral atherosclerosis: Observations from the Dallas Heart Study

Background Peptidoglycan recognition protein-1 (PGLYRP-1) is part of the innate immune system and binds to peptidoglycan, a component of bacterial cell walls that has been found in human atherosclerotic lesions. Chronic exposure to bacterial antigens may cause or exacerbate the inflammatory response to lipid deposition within arterial walls. We hypothesized that PGLYRP-1 is associated with subclinical atherosclerosis as measured by computed tomography and magnetic resonance imaging. Methods and results PGLYRP-1 was measured in 3222 subjects in the Dallas Heart Study, a probability-based population sample age 30–65 including 50% African-Americans and 56% women. Coronary artery calcium (CAC) was measured by electron beam computed tomography ( n = 2467), abdominal aortic wall thickness (AWT) by magnetic resonance imaging (MRI) ( n = 2270), and abdominal aortic plaque burden (APB) by MRI ( n = 2256). In univariable analyses, increasing levels of PGLYRP-1 were associated with all major cardiovascular risk factors, with inflammatory markers such as C-reactive protein, and with CAC, AWT, and APB ( p < 0.0001 for each). In multivariable models adjusted for traditional risk factors, log PGLYRP-1 remained significantly associated with CAC (OR 1.1, 95% CI 1.01–1.3 per S.D.; p = 0.04) and AWT ( p = 0.009) but not APB ( p = 0.09). Further adjustment for novel biomarkers associated with PGLYRP-1 and atherosclerosis attenuated the association with CAC ( p = 0.18) but not with AWT ( p = 0.01) or APB ( p = 0.037). Conclusion In this first reported clinical study of PGLYRP-1 in humans, PGLYRP-1 levels were independently associated with atherosclerosis phenotypes that represent different vascular beds and stages of atherosclerosis.