TLR4-dependent lipopolysaccharide-induced shedding of tumor necrosis factor receptors in mouse bone marrow granulocytes

J Biol Chem. 2003 Jun 6;278(23):20555-64. doi: 10.1074/jbc.M203551200. Epub 2003 Mar 27.

Abstract

We reported previously that bone marrow granulocytes respond to small amounts of enterobacterial lipopolysaccharide (LPS) via a CD14-independent and TLR4-mediated mechanism by de novo expression of an inducible receptor (CD14) and by down-modulation of a constitutive receptor (L-selectin). In this report we address another effect of LPS: the down-regulation of receptors for tumor necrosis factor-alpha. In mouse bone marrow cells (BMC), this down-regulation is detectable soon (20 min) after exposure of the cells to low levels (0.5 ng/ml) of LPS. This temperature-dependent effect is rather selective for LPS and requires the presence of a conventional lipid A structure in the LPS molecule and a functional TLR4 molecule in the cells. The down-modulation, due to a shedding of the receptors, is blocked by p38 MAPK inhibitors, by a furin inhibitor, and by three metalloproteinase inhibitors (BB-3103, TIMP-2, and TIMP-3). In contrast, inhibitors of MEK, protein kinase C, cAMP-dependent protein kinase, and kinases of the Src family do not block the shedding. Analysis of BMC from mice lacking tumor necrosis factor receptor-1 (CD120a-/-) or tumor necrosis factor receptor-2 (CD120b-/-) indicates that the LPS-induced shedding is specific for CD120b. Thus, exposure of BMC to LPS triggers a rapid shedding of CD120b via a protein kinase C- and Src-independent pathway mediated by p38 MAPK, furin, and metalloproteinase. The additive effects of furin and metalloproteinase inhibitors suggest that these enzymes are involved in parallel shedding pathways.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antigens, CD / genetics
  • Antigens, CD / metabolism*
  • Bone Marrow Cells / metabolism
  • Down-Regulation / drug effects
  • Enzyme Inhibitors / pharmacology
  • Female
  • Furin
  • Granulocytes / metabolism*
  • Hematopoiesis / physiology
  • Lipopolysaccharides / pharmacology*
  • Membrane Glycoproteins / metabolism*
  • Metalloendopeptidases / antagonists & inhibitors
  • Metalloendopeptidases / metabolism
  • Mice
  • Mice, Inbred C3H
  • Mice, Inbred C57BL
  • Mice, Mutant Strains
  • Peptide Fragments / metabolism
  • Protease Inhibitors / pharmacology
  • Receptors, Cell Surface / metabolism*
  • Receptors, Tumor Necrosis Factor / genetics
  • Receptors, Tumor Necrosis Factor / metabolism*
  • Receptors, Tumor Necrosis Factor, Type I
  • Receptors, Tumor Necrosis Factor, Type II
  • Subtilisins / antagonists & inhibitors
  • Subtilisins / pharmacology
  • Toll-Like Receptor 4
  • Toll-Like Receptors

Substances

  • Antigens, CD
  • Enzyme Inhibitors
  • Lipopolysaccharides
  • Membrane Glycoproteins
  • Peptide Fragments
  • Protease Inhibitors
  • Receptors, Cell Surface
  • Receptors, Tumor Necrosis Factor
  • Receptors, Tumor Necrosis Factor, Type I
  • Receptors, Tumor Necrosis Factor, Type II
  • Toll-Like Receptor 4
  • Toll-Like Receptors
  • Subtilisins
  • Furin
  • Metalloendopeptidases