Lysophosphatidylcholines activate G2A inducing G(αi)₋₁-/G(αq/)₁₁- Ca²(+) flux, G(βγ)-Hck activation and clathrin/β-arrestin-1/GRK6 recruitment in PMNs

Biochem J. 2010 Nov 15;432(1):35-45. doi: 10.1042/BJ20091087.

Abstract

Lyso-PCs (lysophosphatidylcholines) are a mixture of lipids that accumulate during storage of cellular blood components, have been implicated in TRALI (transfusion-related acute lung injury) and directly affect the physiology of neutrophils [PMNs (polymorphonuclear leucocytes)]. Because the G2A receptor, expressed on PMNs, has been reported to recognize lyso-PCs, we hypothesize that lyso-PC activation of G2A causes the increases in cytosolic Ca²(+) via release of G(α) and G(βγ) subunits, kinase activation, and the recruitment of clathrin, β-arrestin-1 and GRK6 (G-protein receptor kinase 6) to G2A for signal transduction. PMNs were isolated by standard techniques, primed with lyso-PCs for 5-180 s, and lysed for Western blot analysis, immunoprecipitation or subcellular fractionation, or fixed and smeared on to slides for digital microscopy. The results demonstrated that lyso-PCs cause rapid activation of the G2A receptor through S-phosphorylation and internalization resulting in G(αi)₋₁ and G(αq/)₁₁ release leading to increases in cytosolic Ca²(+), which was inhibited by an antibody to G2A or intracellular neutralization of these subunits. Lyso-PCs also caused the release of the G(βγ) subunit which demonstrated a physical interaction (FRET+) with activated Hck (haemopoietic cell kinase; Tyr⁴¹¹). Moreover, G2A recruited clathrin, β-arrestin-1 and GRK6: clathrin is important for signal transduction, GRK6 for receptor de-sensitization, and β-arrestin-1 both propagates and terminates signals. We conclude that lyso-PC activation of G2A caused release of G(αi)₋₁, G(αq/)₁₁ and G(βγ), resulting in cytosolic Ca²(+) flux, Hck activation, and recruitment of clathrin, β-arrestin-1 and GRK6.

Publication types

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

MeSH terms

  • Arrestins / metabolism
  • Blotting, Western
  • Calcium / metabolism*
  • Cell Cycle Proteins / metabolism*
  • Cells, Cultured
  • Clathrin / metabolism
  • Cytosol / drug effects
  • Cytosol / metabolism
  • Enzyme Activation / drug effects
  • Fluorescence Resonance Energy Transfer
  • G-Protein-Coupled Receptor Kinases / metabolism
  • GTP-Binding Protein alpha Subunits / metabolism
  • GTP-Binding Protein beta Subunits / metabolism
  • GTP-Binding Protein gamma Subunits / metabolism
  • Heterotrimeric GTP-Binding Proteins / metabolism*
  • Humans
  • Ion Transport / drug effects
  • Lysophosphatidylcholines / pharmacology*
  • Microscopy, Fluorescence / methods
  • Neutrophils / cytology
  • Neutrophils / drug effects*
  • Neutrophils / metabolism
  • Phosphorylation / drug effects
  • Protein Kinases / metabolism*
  • Proto-Oncogene Proteins c-hck / metabolism
  • Receptors, G-Protein-Coupled / metabolism*
  • Signal Transduction / drug effects
  • Time Factors
  • beta-Arrestin 1
  • beta-Arrestins

Substances

  • ARRB1 protein, human
  • Arrestins
  • Cell Cycle Proteins
  • Clathrin
  • G2A receptor
  • GTP-Binding Protein alpha Subunits
  • GTP-Binding Protein beta Subunits
  • GTP-Binding Protein gamma Subunits
  • Lysophosphatidylcholines
  • Receptors, G-Protein-Coupled
  • beta-Arrestin 1
  • beta-Arrestins
  • Protein Kinases
  • HCK protein, human
  • Proto-Oncogene Proteins c-hck
  • G-Protein-Coupled Receptor Kinases
  • G-protein-coupled receptor kinase 6
  • Heterotrimeric GTP-Binding Proteins
  • Calcium