Lysophospholipids of different classes mobilize neutrophil secretory vesicles and induce redundant signaling through G2A

J Immunol. 2007 May 15;178(10):6540-8. doi: 10.4049/jimmunol.178.10.6540.

Abstract

Lysophosphatidylcholine has been shown to enhance neutrophil functions through a mechanism involving the G protein-coupled receptor G2A. Recent data support an indirect effect of lysophosphatidylcholine on G2A rather than direct ligand binding. These observations prompted the hypothesis that other lysophospholipids (lyso-PLs) may also signal for human neutrophil activation through G2A. To this end, 1-oleoyl-2-hydroxy-sn-glycero-3-[phospho-L-choline], but also C18:1/OH lyso-PLs bearing the phosphoserine and phosphoethanolamine head groups, presented on albumin, were shown to signal for calcium flux in a self- and cross-desensitizing manner, implicating a single receptor. Blocking Abs to G2A inhibited calcium signaling by all three lyso-PLs. Furthermore, inhibition by both pertussis toxin and U-73122 established signaling via the Galphai/phospholipase C pathway for calcium mobilization. Altered plasma membrane localization of G2A has been hypothesized to facilitate signaling. Accordingly, an increase in detectable G2A was demonstrated by 1 min after lyso-PL stimulation and was followed by visible patching of the receptor. Western blotting showed that G2A resides in the plasma membrane/secretory vesicle fraction and not in neutrophil primary, secondary, or tertiary granules. Enhanced detection of G2A induced by lyso-PLs was paralleled by enhanced detection of CD45, confirming mobilization of the labile secretory vesicle pool. Together, these data show that lyso-PLs bearing various head groups redundantly mobilize G2A latent within secretory vesicles and result in G2A receptor/Galphai/phospholipase C signaling for calcium flux in neutrophils.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Calcium Signaling / immunology*
  • Cell Cycle Proteins / physiology*
  • Cells, Cultured
  • GTP-Binding Protein alpha Subunits, Gi-Go / physiology
  • Humans
  • Lysophospholipids / blood*
  • Lysophospholipids / classification*
  • Lysophospholipids / physiology
  • Neutrophil Activation / immunology*
  • Neutrophils / enzymology
  • Neutrophils / immunology*
  • Neutrophils / metabolism*
  • Receptors, G-Protein-Coupled / physiology*
  • Secretory Vesicles / immunology
  • Secretory Vesicles / metabolism*
  • Type C Phospholipases / physiology

Substances

  • Cell Cycle Proteins
  • G2A receptor
  • Lysophospholipids
  • Receptors, G-Protein-Coupled
  • Type C Phospholipases
  • GTP-Binding Protein alpha Subunits, Gi-Go