Platelet-activating factor receptor and innate immunity: uptake of gram-positive bacterial cell wall into host cells and cell-specific pathophysiology

J Immunol. 2006 Nov 1;177(9):6182-91. doi: 10.4049/jimmunol.177.9.6182.

Abstract

The current model of innate immune recognition of Gram-positive bacteria suggests that the bacterial cell wall interacts with host recognition proteins such as TLRs and Nod proteins. We describe an additional recognition system mediated by the platelet-activating factor receptor (PAFr) and directed to the pathogen-associated molecular pattern phosphorylcholine that results in the uptake of bacterial components into host cells. Intravascular choline-containing cell walls bound to endothelial cells and caused rapid lethality in wild-type, Tlr2(-/-), and Nod2(-/-) mice but not in Pafr(-/-) mice. The cell wall exited the vasculature into the heart and brain, accumulating within endothelial cells, cardiomyocytes, and neurons in a PAFr-dependent way. Physiological consequences of the cell wall/PAFr interaction were cell specific, being noninflammatory in endothelial cells and neurons but causing a rapid loss of cardiomyocyte contractility that contributed to death. Thus, PAFr shepherds phosphorylcholine-containing bacterial components such as the cell wall into host cells from where the response ranges from quiescence to severe pathophysiology.

MeSH terms

  • Animals
  • Cell Wall / chemistry
  • Cell Wall / metabolism*
  • Endothelium, Vascular / cytology
  • Endothelium, Vascular / metabolism
  • Endothelium, Vascular / microbiology
  • Gram-Positive Bacteria / immunology
  • Immunity, Innate* / genetics
  • Mice
  • Mice, Mutant Strains
  • Myocytes, Cardiac / metabolism
  • Neurons / metabolism
  • Nod2 Signaling Adaptor Protein / genetics
  • Nod2 Signaling Adaptor Protein / physiology
  • Phosphorylcholine / analysis
  • Platelet Membrane Glycoproteins / genetics
  • Platelet Membrane Glycoproteins / physiology*
  • Pneumococcal Infections / immunology*
  • Pneumococcal Infections / microbiology
  • Pneumococcal Infections / physiopathology
  • Rats
  • Receptors, G-Protein-Coupled / genetics
  • Receptors, G-Protein-Coupled / physiology*
  • Streptococcus pneumoniae / immunology
  • Toll-Like Receptor 2 / genetics
  • Toll-Like Receptor 2 / physiology

Substances

  • Nod2 Signaling Adaptor Protein
  • Nod2 protein, mouse
  • Platelet Membrane Glycoproteins
  • Receptors, G-Protein-Coupled
  • Tlr2 protein, mouse
  • Toll-Like Receptor 2
  • platelet activating factor receptor
  • Phosphorylcholine