Control of intestinal Nod2-mediated peptidoglycan recognition by epithelium-associated lymphocytes

Mucosal Immunol. 2011 May;4(3):325-34. doi: 10.1038/mi.2010.71. Epub 2010 Oct 27.

Abstract

Innate immune recognition of the bacterial cell wall constituent peptidoglycan by the cytosolic nucleotide-binding oligomerization domain 2 (Nod2) receptor has a pivotal role in the maintenance of intestinal mucosal homeostasis. Whereas peptidoglycan cleavage by gut-derived lysozyme preserves the recognition motif, the N-acetylmuramoyl-L-alanine amidase activity of the peptidoglycan recognition protein 2 (PGLYRP-2) destroys the Nod2-detected muramyl dipeptide structure. PGLYRP-2 green fluorescent protein (GFP) reporter and wild-type mice were studied by flow cytometry and quantitative RT-PCR to identify Pglyrp-2 expression in cells of the intestinal mucosa and reveal a potential regulatory function on epithelial peptidoglycan recognition. CD3(+)/CD11c(+) T lymphocytes revealed significant Pglyrp-2 expression, whereas epithelial cells and intestinal myeloid cells were negative. The mucosal Pglyrp-2-expressing lymphocyte population demonstrated a mixed T-cell receptor (TCR) αβ or γδ phenotype with predominant CD8α and less so CD8β expression, as well as significant staining for the activation markers B220 and CD69, presenting a typical intraepithelial lymphocyte phenotype. Importantly, exposure of peptidoglycan to PGLYRP-2 significantly reduced Nod2/Rip2-mediated epithelial activation. Also, moderate but significant alterations of the intestinal microbiota composition were noted in Pglyrp-2-deficient animals. PGLYRP-2 might thus have a significant role in regulation of the enteric host-microbe homeostasis.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antigens, CD / metabolism
  • Cells, Cultured
  • Genetic Engineering
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • Host-Pathogen Interactions
  • Intestinal Mucosa / immunology
  • Intestinal Mucosa / metabolism*
  • Intestinal Mucosa / microbiology
  • Intestinal Mucosa / pathology
  • Lymphocyte Activation
  • Metagenome
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • N-Acetylmuramoyl-L-alanine Amidase / metabolism*
  • Nod2 Signaling Adaptor Protein / genetics
  • Nod2 Signaling Adaptor Protein / immunology
  • Nod2 Signaling Adaptor Protein / metabolism*
  • Peptidoglycan / immunology
  • Proteins / genetics
  • Proteins / immunology
  • Proteins / metabolism*
  • Receptors, Antigen, T-Cell / metabolism
  • T-Lymphocytes / immunology
  • T-Lymphocytes / metabolism*
  • T-Lymphocytes / pathology

Substances

  • Antigens, CD
  • Nod2 Signaling Adaptor Protein
  • Nod2 protein, mouse
  • Peptidoglycan
  • Proteins
  • Receptors, Antigen, T-Cell
  • Green Fluorescent Proteins
  • N-Acetylmuramoyl-L-alanine Amidase
  • Pglyrp2 protein, mouse