Biology:Peptidoglycan recognition protein 2

From HandWiki
Short description: Protein-coding gene in the species Homo sapiens

Peptidoglycan recognition protein 2 (PGLYRP2) is an enzyme (EC 3.5.1.28), N-acetylmuramoyl-L-alanine amidase (NAMLAA), that hydrolyzes bacterial cell wall peptidoglycan and is encoded by the PGLYRP2 gene.[1][2][3][4][5][6]

A representation of the 3D structure of the protein myoglobin showing turquoise α-helices.
Generic protein structure example


Discovery

The N-acetylmuramoyl-L-alanine amidase enzymatic activity was first observed in human and mouse serum in 1981 by Branko Ladešić and coworkers.[7] The enzyme (abbreviated NAMLAA) was then purified from human serum by this[8] and other groups.[9][10][11][12] The sequence of 15 N-terminal amino acids of NAMLAA was identified,[11] but the cDNA for the protein was not cloned and the gene encoding NAMLAA was not known.

In 2000, Dan Hultmark and coworkers discovered a family of 12 Peptidoglycan Recognition Protein (PGRP) genes in Drosophila melanogaster and by homology searches of available human and mouse sequences predicted the presence of long forms of human and mouse PGRPs, which they named PGRP-L by analogy to long forms of insect PGRPs.[13]

In 2001, Roman Dziarski and coworkers discovered and cloned three human PGRPs, named PGRP-L, PGRP-Iα, and PGRP-Iβ (for long and intermediate size transcripts),[1] and established that human genome codes for a family of 4 PGRPs: PGRP-S (short PGRP)[14] and PGRP-L, PGRP-Iα, and PGRP-Iβ.[1] Subsequently, the Human Genome Organization Gene Nomenclature Committee changed the gene symbols of PGRP-S, PGRP-L, PGRP-Iα, and PGRP-Iβ to PGLYRP1 (peptidoglycan recognition protein 1), PGLYRP2 (peptidoglycan recognition protein 2), PGLYRP3 (peptidoglycan recognition protein 3), and PGLYRP4 (peptidoglycan recognition protein 4), respectively, and this nomenclature is currently also used for other mammalian PGRPs. Sergei Kiselev and coworkers also independently cloned mouse PGLYRP2 (which they named TagL).[2][15] File:Human PGLYRP2 gene, cDNA, and protein rev.tif In 2003 Håkan Steiner and coworkers[3] and Roman Dziarski and coworkers[4] discovered that mouse[3] and human[4] PGLYRP2 (PGRP-L) proteins encoded by the mouse and human PGLYRP2 genes are N-acetylmuramoyl-L-alanine amidases. Recombinant and native human PGLYRP2 proteins were then further shown to be identical with the previously identified and purified serum NAMLAA.[16]

Tissue distribution and secretion

Human and mouse PGLYRP2 is constitutively expressed in the adult and fetal liver, from where it is secreted into the blood.[1][3][16][17][18] PGLYRP2 (NAMLAA) is present in human plasma at 100 to 200 µg/ml[12][19] and at lower concentrations in saliva, milk, cerebrospinal fluid, and synovial fluid.[19] PGLYRP2 is also expressed to a much lower level in the colon, lymph nodes, spleen, thymus, heart, and polymorphonuclear leukocyte granules.[1][20][21] PGLYRP2 is differentially expressed in the developing brain and this expression is influenced by the intestinal microbiome.[22] Bacteria and cytokines induce low level of PGLYRP2 expression in the skin and gastrointestinal and oral epithelial cells,[18][23][24][25][26] and also in intestinal intraepithelial T lymphocytes, dendritic cells, NK (natural killer) cells, and inflammatory macrophages.[27][28] Some mammals, e.g. pigs, express multiple splice forms of PGLYRP2 with differential expression.[29]

Bacteria and cytokines induce expression of PGLYRP2 in epithelial cells through the p38 mitogen activated protein kinase (MAPK) and IRAK1 (interleukin-1 receptor-associated kinase 1) signaling pathways.[23][26] Constitutive and induced expression of PGLYRP2 is controlled by different transcription factors whose binding sequences are located in different regions of the PGLYRP2 promoter.[18] Constitutive expression of PGLYRP2 in hepatocytes is regulated by transcription factors c-Jun and ATF2 (activating transcription factor 2) through sequences in the proximal region of the promoter.[18] Induced expression of PGLYRP2 in keratinocytes is regulated by transcription factors NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells) and Sp1 (specificity protein 1) through sequences in the distal region of the promoter.[18]

Structure

PGLYRP2 has one canonical carboxy-terminal catalytic peptidoglycan-binding type 2 amidase domain (also known as a PGRP domain) with predicted peptidoglycan-binding and catalytic cleft with walls formed by α-helices and the floor by a β-sheet.[1][3][30] PGLYRP2 also has a long N-terminal segment that comprises two thirds of the PGLYRP2 sequence, has two hydrophobic regions, is not found in other mammalian PGLYRP1, PGLYRP3, and PGLYRP4 and in invertebrate PGRPs, and is unique with no identifiable functional motifs or domains.[1][3][30] The C-terminal segment is also longer than in other mammalian PGLYRPs.[1][3][30] PGLYRP2 has two pairs of cysteines in the PGRP domain that are conserved in all human PGRPs and are predicted to form two disulfide bonds.[1] Human PGLYRP2 is glycosylated[9][11] and secreted,[8][9][10][11][12][16][17] and forms non-disulfide-linked homodimers.[11]

PGLYRP2, similar to all other amidase-active PGRPs (invertebrate and vertebrate), has a conserved Zn2+-binding site in the peptidoglycan-binding cleft, which is also present in bacteriophage type 2 amidases and consists of two histidines, one tyrosine, and one cysteine (His411, Tyr447, His522, Cys530 in human PGLYRP2).[4]

Functions

The PGLYRP2 protein plays an important role in the innate immune responses.

Peptidoglycan binding and hydrolysis

PGLYRP2 is an enzyme (EC 3.5.1.28), N-acetylmuramoyl-L-alanine amidase, that binds and hydrolyzes bacterial cell wall peptidoglycan.[1][3][4][7][8][9][10][11][12][31] Peptidoglycan is the main component of bacterial cell wall and is a polymer of β(1-4)-linked N-acetylglucosamine (GlcNAc) and N-acetylmuramic acid (MurNAc) with MurNAc-attached short peptides, typically composed of alternating L and D amino acids, that cross-link the adjacent polysaccharide chains.

PGLYRP2 hydrolyzes the amide bond between the MurNAc and L-Ala, the first amino acid in the stem peptide.[3][4][7][8] This hydrolysis separates the crosslinking peptides from the polysaccharide chains and solubilizes cross-linked bacterial peptidoglycan into uncross-linked polysaccharide chains.[4] The minimal peptidoglycan fragment hydrolyzed by PGLYRP2 is MurNAc-tripeptide.[4]

The peptidoglycan-binding site, which is also the amidase catalytic domain, is located in the C-terminal PGRP domain. This PGRP domain is sufficient for the enzymatic activity of PGLYRP2, although this activity of the isolated C-terminal fragment is diminished compared with the entire PGLYRP2 molecule.[4] Zn2+ and Zn2+-binding amino acids (His411, Tyr447, and Cys530 in human PGLYRP2) are required for the amidase activity.[4] Cys419 in human PGLYRP2, which is broadly conserved in invertebrate and vertebrate PRGPs, forms a disulfide bond with Cys425 (in human PGLYRP2) and is required for the amidase activity, as this disulfide bond is essential for the structural integrity of the PGRP domain.[4] Cys530 is conserved in all amidase-active vertebrate and invertebrate PGRPs, whereas non-catalytic PGRPs (including mammalian PGLYRP1, PGLYRP3, and PGLYRP4) have serine in this position,[1] and thus the presence of Cys or Ser in this position can be used to predict amidase activity of PGRPs.[4] However, Cys530 and seven other amino acids that are all required for the amidase activity of PGRPs are not sufficient for the amidase activity, which requires additional so far unidentified amino acids.[4]

Defense against infections

PGLYRP2 plays a limited role in host defense against infections. PGLYRP2-deficient mice are more sensitive to Pseudomonas aeruginosa-induced keratitis[32] and Streptococcus pneumoniae-induced pneumonia and sepsis.[33] However, PGLYRP2-deficient mice did not show a changed susceptibility to systemic Escherichia coli, Staphylococcus aureus, and Candida albicans infections[17] or intestinal Salmonella enterica infection,[28] although the latter was accompanied by increased inflammation in the cecum.[27]

Although PGLYRP2 is not directly bacteriolytic,[4] it has antibacterial activity against both Gram-positive and Gram-negative bacteria and Chlamydia trachomatis.[34]

Maintaining microbiome

Mouse PGLYRP2 plays a role in maintaining healthy microbiome, as PGLYRP2-deficient mice have significant changes in the composition of their intestinal microbiome, which affect their sensitivity to colitis.[35][36]

Effects on inflammation

PGLYRP2 directly and indirectly affects inflammation and plays a role in maintaining anti- and pro-inflammatory homeostasis in the intestine, skin, joints, and brain.

Hydrolysis of peptidoglycan by PGLYRP2 diminishes peptidoglycan’s pro-inflammatory activity.[27][37] This effect is likely due to amidase activity of PGLYRP2, which separates the stem peptide from MurNAc in peptidoglycan and destroys the motif required for the peptidoglycan-induced activation of NOD2 (nucleotide-binding oligomerization domain-containing protein 2), one of the proinflammatory peptidoglycan receptors.[27]

PGLYRP2-deficient mice are more susceptible than wild type mice to dextran sodium sulfate (DSS)-induced colitis, which indicates that PGLYRP2 protects mice from DSS-induced colitis.[35] Intestinal microbiome is important for this protection, because this increased sensitivity to colitis could be transferred to wild type germ-free mice by microbiome transplant from PGLYRP2-deficient mice.[35]

PGLYRP2-deficient mice are more susceptible than wild type mice to the development of experimentally induced psoriasis-like inflammation,[38] which indicates that PGLYRP2 is anti-inflammatory and protects mice from this type of skin inflammation. This pro-inflammatory effect in PGLYRP2-deficient mice is due to the increased numbers and activity of T helper 17 (Th17) cells and decreased numbers of T regulatory (Treg) cells.[38] PGLYRP2-deficient mice are more susceptible than wild type mice to S. enterica-induced intestinal inflammation,[28] which indicates that PGLYRP2 also has anti-inflammatory effect in the intestinal tract.

However, PGLYRP2 also has opposite effects. PGLYRP2-deficient mice are more resistant than wild type mice to the development of arthritis induced by systemic administration of peptidoglycan or MurNAc-L-Ala-D-isoGln peptidoglycan fragment (muramyl dipeptide, MDP).[39] In this model, PGLYRP2 is required for the production of chemokines and cytokines that attract neutrophils to the arthritic joints.[39] PGLYRP2-deficient mice are also more resistant than wild type mice to bacterially induced keratitis[32] and inflammation in S. pneumoniae-induced lung infection.[33] Moreover, PGLYRP2-deficient mice are more resistant to weight loss in a model of chemotherapy-induced gastrointestinal toxicity, which indicates that in wild type mice PGLYRP2 contributes to the chemotherapy-induced weight loss.[40] These results indicate that under certain conditions PGLYRP2 has pro-inflammatory effects.[32][33][39]

PGLYRP2-deficient mice also show higher sociability and decreased levels of anxiety-like behaviors compared with wild type mice, which indicate that PGLYRP2 affects behavior in mice.[22][41]

Medical relevance

Genetic PGLYRP2 variants or changed expression of PGLYRP2 are associated with some diseases. Patients with inflammatory bowel disease (IBD), which includes Crohn’s disease and ulcerative colitis, have significantly more frequent missense variants in PGLYRP2 gene (and also in the other three PGLYRP genes) than healthy controls.[30] These results suggest that PGLYRP2 protects humans from these inflammatory diseases, and that mutations in PGLYRP2 gene are among the genetic factors predisposing to these diseases. PGLYRP2 variants are also associated with esophageal squamous cell carcinoma[42] and Parkinson’s disease.[43][44][45]

Increased serum PGLYRP2 levels are present in patients with systemic lupus erythematosus and correlate with disease activity index, renal damage, and abnormal lipid profile.[46]

Decreased expression of PGLYRP2 is found in HIV-associated tuberculosis,[47] drug-sensitive tuberculosis,[48] Lyme disease,[49] hepatocellular carcinoma,[50] and myocardial infarction.[51]

Autoantibodies to PGLYRP2 are significantly increased in patients with rheumatoid arthritis.[52]

See also

References

  1. 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 "Peptidoglycan recognition proteins: a novel family of four human innate immunity pattern recognition molecules". The Journal of Biological Chemistry 276 (37): 34686–94. September 2001. doi:10.1074/jbc.M105566200. PMID 11461926. 
  2. 2.0 2.1 "Molecular cloning of a new mouse gene tagL containing a lysozyme-like domain". Doklady Biochemistry 372 (1–6): 103–5. May 2000. PMID 10935177. 
  3. 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 "A mammalian peptidoglycan recognition protein with N-acetylmuramoyl-L-alanine amidase activity". Biochemical and Biophysical Research Communications 306 (4): 988–94. July 2003. doi:10.1016/s0006-291x(03)01096-9. PMID 12821140. 
  4. 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 4.10 4.11 4.12 4.13 "Human peptidoglycan recognition protein-L is an N-acetylmuramoyl-L-alanine amidase". The Journal of Biological Chemistry 278 (49): 49044–52. December 2003. doi:10.1074/jbc.M307758200. PMID 14506276. 
  5. "PGLYRP2 peptidoglycan recognition protein 2 [Homo sapiens (human) - Gene - NCBI"]. https://www.ncbi.nlm.nih.gov/gene?Db=gene&Cmd=ShowDetailView&TermToSearch=114770. 
  6. "Pglyrp2 peptidoglycan recognition protein 2 [Mus musculus (house mouse) - Gene - NCBI"]. https://www.ncbi.nlm.nih.gov/gene/57757. 
  7. 7.0 7.1 7.2 "The metabolic fate of 14C-labeled immunoadjuvant peptidoglycan monomer. II. In vitro studies". Biochimica et Biophysica Acta 678 (1): 12–7. November 1981. doi:10.1016/0304-4165(81)90042-8. PMID 6118181. 
  8. 8.0 8.1 8.2 8.3 "Partial purification and characterization of N-acetylmuramyl-L-alanine amidase from human and mouse serum". Biochimica et Biophysica Acta 701 (1): 63–71. February 1982. doi:10.1016/0167-4838(82)90313-2. PMID 6120007. 
  9. 9.0 9.1 9.2 9.3 "Murein hydrolase (N-acetyl-muramyl-L-alanine amidase) in human serum". Archives of Microbiology 140 (2–3): 171–7. December 1984. doi:10.1007/BF00454921. PMID 6152147. Bibcode1984ArMic.140..171M. 
  10. 10.0 10.1 10.2 "Purification and characterization of N-acetylmuramoyl-L-alanine amidase from human serum". Biochimica et Biophysica Acta 1039 (3): 331–8. July 1990. doi:10.1016/0167-4838(90)90267-j. PMID 1974148. 
  11. 11.0 11.1 11.2 11.3 11.4 11.5 "Characterization of human serum N-acetylmuramyl-L-alanine amidase purified by affinity chromatography". Protein Expression and Purification 6 (3): 371–8. June 1995. doi:10.1006/prep.1995.1049. PMID 7663175. 
  12. 12.0 12.1 12.2 12.3 "Purification and characterization of N-acetylmuramyl-L-alanine amidase from human plasma using monoclonal antibodies". Biochimica et Biophysica Acta (BBA) - General Subjects 1289 (1): 57–64. February 1996. doi:10.1016/0304-4165(95)00136-0. PMID 8605233. http://repub.eur.nl/pub/62308. 
  13. "A family of peptidoglycan recognition proteins in the fruit fly Drosophila melanogaster". Proceedings of the National Academy of Sciences of the United States of America 97 (25): 13772–7. December 2000. doi:10.1073/pnas.97.25.13772. PMID 11106397. Bibcode2000PNAS...9713772W. 
  14. "A peptidoglycan recognition protein in innate immunity conserved from insects to humans". Proceedings of the National Academy of Sciences of the United States of America 95 (17): 10078–82. August 1998. doi:10.1073/pnas.95.17.10078. PMID 9707603. Bibcode1998PNAS...9510078K. 
  15. "The differentially spliced mouse tagL gene, homolog of tag7/PGRP gene family in mammals and Drosophila, can recognize Gram-positive and Gram-negative bacterial cell wall independently of T phage lysozyme homology domain". Journal of Molecular Biology 326 (2): 467–74. February 2003. doi:10.1016/s0022-2836(02)01401-8. PMID 12559914. 
  16. 16.0 16.1 16.2 "Identification of serum N-acetylmuramoyl-l-alanine amidase as liver peptidoglycan recognition protein 2". Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics 1752 (1): 34–46. August 2005. doi:10.1016/j.bbapap.2005.07.001. PMID 16054449. 
  17. 17.0 17.1 17.2 "Innate immune responses in peptidoglycan recognition protein L-deficient mice". Molecular and Cellular Biology 24 (18): 7949–57. September 2004. doi:10.1128/MCB.24.18.7949-7957.2004. PMID 15340057. 
  18. 18.0 18.1 18.2 18.3 18.4 "Differential expression of peptidoglycan recognition protein 2 in the skin and liver requires different transcription factors". The Journal of Biological Chemistry 281 (30): 20738–48. July 2006. doi:10.1074/jbc.M601017200. PMID 16714290. 
  19. 19.0 19.1 "The human and mammalian N-acetylmuramyl-L-alanine amidase: distribution, action on different bacterial peptidoglycans, and comparison with the human lysozyme activities". Biochemical and Molecular Medicine 54 (1): 26–32. February 1995. doi:10.1006/bmme.1995.1004. PMID 7551813. 
  20. "Expression and intracellular localization of the human N-acetylmuramyl-L-alanine amidase, a bacterial cell wall-degrading enzyme". Blood 90 (3): 1246–54. August 1997. doi:10.1182/blood.V90.3.1246. PMID 9242559. 
  21. "Differences in N-acetylmuramyl-L-alanine amidase and lysozyme in serum and cerebrospinal fluid of patients with bacterial meningitis". The Journal of Infectious Diseases 177 (1): 102–6. January 1998. doi:10.1086/513815. PMID 9419176. 
  22. 22.0 22.1 "The bacterial peptidoglycan-sensing molecule Pglyrp2 modulates brain development and behavior". Molecular Psychiatry 22 (2): 257–266. February 2017. doi:10.1038/mp.2016.182. PMID 27843150. 
  23. 23.0 23.1 "Peptidoglycan recognition protein 2 (N-acetylmuramoyl-L-Ala amidase) is induced in keratinocytes by bacteria through the p38 kinase pathway". Infection and Immunity 73 (11): 7216–25. November 2005. doi:10.1128/IAI.73.11.7216-7225.2005. PMID 16239516. 
  24. "Peptidoglycan recognition proteins are a new class of human bactericidal proteins". The Journal of Biological Chemistry 281 (9): 5895–907. March 2006. doi:10.1074/jbc.M511631200. PMID 16354652. 
  25. "Chemically synthesized pathogen-associated molecular patterns increase the expression of peptidoglycan recognition proteins via toll-like receptors, NOD1 and NOD2 in human oral epithelial cells". Cellular Microbiology 7 (5): 675–86. May 2005. doi:10.1111/j.1462-5822.2004.00500.x. PMID 15839897. 
  26. 26.0 26.1 "Regulation of the Peptidoglycan Amidase PGLYRP2 in Epithelial Cells by Interleukin-36γ". Infection and Immunity 86 (9). September 2018. doi:10.1128/IAI.00384-18. PMID 29914927. 
  27. 27.0 27.1 27.2 27.3 "Control of intestinal Nod2-mediated peptidoglycan recognition by epithelium-associated lymphocytes". Mucosal Immunology 4 (3): 325–34. May 2011. doi:10.1038/mi.2010.71. PMID 20980996. 
  28. 28.0 28.1 28.2 "Role of mouse peptidoglycan recognition protein PGLYRP2 in the innate immune response to Salmonella enterica serovar Typhimurium infection in vivo". Infection and Immunity 80 (8): 2645–54. August 2012. doi:10.1128/IAI.00168-12. PMID 22615249. 
  29. "Gene silencing and overexpression of porcine peptidoglycan recognition protein long isoforms: involvement in beta-defensin-1 expression". Infection and Immunity 73 (11): 7133–41. November 2005. doi:10.1128/IAI.73.11.7133-7141.2005. PMID 16239507. 
  30. 30.0 30.1 30.2 30.3 "Genetic Association of Peptidoglycan Recognition Protein Variants with Inflammatory Bowel Disease". PLOS ONE 8 (6): e67393. 2013. doi:10.1371/journal.pone.0067393. PMID 23840689. Bibcode2013PLoSO...867393Z. 
  31. "Reactome | PGLYRP2 hydrolyzes bacterial peptidoglycan". https://reactome.org/content/detail/R-HSA-6799977. 
  32. 32.0 32.1 32.2 "Functions of Peptidoglycan Recognition Proteins (Pglyrps) at the Ocular Surface: Bacterial Keratitis in Gene-Targeted Mice Deficient in Pglyrp-2, -3 and -4". PLOS ONE 10 (9): e0137129. 2015. doi:10.1371/journal.pone.0137129. PMID 26332373. Bibcode2015PLoSO..1037129G. 
  33. 33.0 33.1 33.2 "Streptococcus pneumoniae Infection". Frontiers in Microbiology 10: 199. 2019. doi:10.3389/fmicb.2019.00199. PMID 30837960. 
  34. "Recombinant Human Peptidoglycan Recognition Proteins Reveal Antichlamydial Activity". Infection and Immunity 84 (7): 2124–2130. July 2016. doi:10.1128/IAI.01495-15. PMID 27160295. 
  35. 35.0 35.1 35.2 "Peptidoglycan recognition proteins protect mice from experimental colitis by promoting normal gut flora and preventing induction of interferon-gamma". Cell Host & Microbe 8 (2): 147–62. August 2010. doi:10.1016/j.chom.2010.07.005. PMID 20709292. 
  36. "Pglyrp-Regulated Gut Microflora Prevotella falsenii, Parabacteroides distasonis and Bacteroides eggerthii Enhance and Alistipes finegoldii Attenuates Colitis in Mice". PLOS ONE 11 (1): e0146162. 2016. doi:10.1371/journal.pone.0146162. PMID 26727498. Bibcode2016PLoSO..1146162D. 
  37. "Inflammatory properties of peptidoglycan are decreased after degradation by human N-acetylmuramyl-L-alanine amidase". European Cytokine Network 8 (4): 375–81. December 1997. PMID 9459617. 
  38. 38.0 38.1 "Peptidoglycan recognition protein Pglyrp2 protects mice from psoriasis-like skin inflammation by promoting regulatory T cells and limiting Th17 responses". Journal of Immunology 187 (11): 5813–23. December 2011. doi:10.4049/jimmunol.1101068. PMID 22048773. 
  39. 39.0 39.1 39.2 "PGLYRP-2 and Nod2 are both required for peptidoglycan-induced arthritis and local inflammation". Cell Host & Microbe 5 (2): 137–50. February 2009. doi:10.1016/j.chom.2008.12.010. PMID 19218085. 
  40. Bech, Ann-Sophie; Nexoe, Anders Bathum; Dubik, Magdalena; Moeller, Jesper Bonnet; Soerensen, Grith Lykke; Holmskov, Uffe; Madsen, Gunvor Iben; Husby, Steffen et al. (2021-03-23). "Peptidoglycan Recognition Peptide 2 Aggravates Weight Loss in a Murine Model of Chemotherapy-Induced Gastrointestinal Toxicity". Frontiers in Oncology 11. doi:10.3389/fonc.2021.635005. ISSN 2234-943X. PMID 33833993. 
  41. "Sex-dependent alterations in motor and anxiety-like behavior of aged bacterial peptidoglycan sensing molecule 2 knockout mice". Brain, Behavior, and Immunity 67: 345–354. January 2018. doi:10.1016/j.bbi.2017.09.014. PMID 28951252. 
  42. "Replication of a genome-wide case-control study of esophageal squamous cell carcinoma". International Journal of Cancer 123 (7): 1610–5. October 2008. doi:10.1002/ijc.23682. PMID 18649358. 
  43. "Peptidoglycan recognition protein genes and risk of Parkinson's disease". Movement Disorders 29 (9): 1171–80. August 2014. doi:10.1002/mds.25895. PMID 24838182. 
  44. Gorecki, Anastazja M.; Bakeberg, Megan C.; Theunissen, Frances; Kenna, Jade E.; Hoes, Madison E.; Pfaff, Abigail L.; Akkari, P. Anthony; Dunlop, Sarah A. et al. (2020-11-17). "Single Nucleotide Polymorphisms Associated With Gut Homeostasis Influence Risk and Age-at-Onset of Parkinson's Disease". Frontiers in Aging Neuroscience 12. doi:10.3389/fnagi.2020.603849. ISSN 1663-4365. PMID 33328979. 
  45. Luan, Mengting; Jin, Jianing; Wang, Ying; Li, Xiaoyuan; Xie, Anmu (April 2022). "Association of PGLYRP2 gene polymorphism and sporadic Parkinson's disease in northern Chinese Han population" (in en). Neuroscience Letters 775: 136547. doi:10.1016/j.neulet.2022.136547. PMID 35218888. https://linkinghub.elsevier.com/retrieve/pii/S0304394022001045. 
  46. Li, Hui; Meng, Defang; Jia, Jieting; Wei, Hua (December 2021). "PGLYRP2 as a novel biomarker for the activity and lipid metabolism of systemic lupus erythematosus" (in en). Lipids in Health and Disease 20 (1): 95. doi:10.1186/s12944-021-01515-8. ISSN 1476-511X. PMID 34461924. 
  47. "Host Protein Biomarkers Identify Active Tuberculosis in HIV Uninfected and Co-infected Individuals". eBioMedicine 2 (9): 1160–8. September 2015. doi:10.1016/j.ebiom.2015.07.039. PMID 26501113. 
  48. Chen, Jing; Han, Yu-Shuai; Yi, Wen-Jing; Huang, Huai; Li, Zhi-Bin; Shi, Li-Ying; Wei, Li-Liang; Yu, Yi et al. (November 2020). "Serum sCD14, PGLYRP2 and FGA as potential biomarkers for multidrug‐resistant tuberculosis based on data‐independent acquisition and targeted proteomics" (in en). Journal of Cellular and Molecular Medicine 24 (21): 12537–12549. doi:10.1111/jcmm.15796. ISSN 1582-1838. PMID 32967043. 
  49. "Measurement of Organ-Specific and Acute-Phase Blood Protein Levels in Early Lyme Disease". Journal of Proteome Research 19 (1): 346–359. January 2020. doi:10.1021/acs.jproteome.9b00569. PMID 31618575. PMC 7981273. https://www.biorxiv.org/content/biorxiv/early/2019/10/08/795344.full.pdf. 
  50. "Tumor-Derived Peptidoglycan Recognition Protein 2 Predicts Survival and Antitumor Immune Responses in Hepatocellular Carcinoma". Hepatology 71 (5): 1626–1642. May 2020. doi:10.1002/hep.30924. PMID 31479523. 
  51. "Proteomic analysis detects deregulated reverse cholesterol transport in human subjects with ST-segment elevation myocardial infarction". Journal of Proteomics 222: 103796. June 2020. doi:10.1016/j.jprot.2020.103796. PMID 32376501. 
  52. Huang, Fei; Liu, Xu; Cheng, Yongjing; Sun, Xiaolin; Li, Yingni; Zhao, Jing; Cao, Di; Wu, Qin et al. (2021-08-31). "Antibody to peptidoglycan recognition protein (PGLYRP)-2 as a novel biomarker in rheumatoid arthritis" (in en). Clinical and Experimental Rheumatology 39 (5): 988–994. doi:10.55563/clinexprheumatol/vlvlqu. ISSN 1593-098X. PMID 33427621. https://www.clinexprheumatol.org/abstract.asp?a=15708. 

Further reading