Autoantibodies to endothelial cell surface ATP synthase, the endogenous receptor for hsp60, might play a pathogenic role in vasculatides

PLoS One. 2011 Feb 7;6(2):e14654. doi: 10.1371/journal.pone.0014654.

Abstract

Background: Heat shock protein (hsp) 60 that provides "danger signal" binds to the surface of resting endothelial cells (EC) but its receptor has not yet been characterized. In mitochondria, hsp60 specifically associates with adenosine triphosphate (ATP) synthase. We therefore examined the possible interaction between hsp60 and ATP synthase on EC surface.

Methodology/principal findings: Using Far Western blot approach, co-immunoprecipitation studies and surface plasmon resonance analyses, we demonstrated that hsp60 binds to the β-subunit of ATP synthase. As a cell surface-expressed molecule, ATP synthase is potentially targeted by anti-EC-antibodies (AECAs) found in the sera of patients suffering vasculitides. Based on enzyme-linked immunosorbent assay and Western blotting techniques with F1-ATP synthase as substrate, we established the presence of anti-ATP synthase antibodies at higher frequency in patients with primary vasculitides (group I) compared with secondary vasculitides (group II). Anti-ATP synthase reactivity from group I patients was restricted to the β-subunit of ATP synthase, whereas those from group II was directed to the α-, β- and γ-subunits. Cell surface ATP synthase regulates intracellular pH (pHi). In low extracellular pH medium, we detected abnormal decreased of EC pHi in the presence of anti-ATP synthase antibodies, irrespective of their fine reactivities. Interestingly, soluble hsp60 abrogated the anti-ATP synthase-induced pHi down-regulation.

Conclusions/significance: Our results indicate that ATP synthase is targeted by AECAs on the surface of EC that induce intracellular acidification. Such pathogenic effect in vasculitides can be modulated by hsp60 binding on ATP synthase which preserves ATP synthase activity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Antigens, Surface / immunology
  • Antigens, Surface / metabolism
  • Autoantibodies / adverse effects
  • Autoantibodies / blood
  • Autoantibodies / metabolism
  • Autoantibodies / physiology*
  • Autoimmune Diseases / blood
  • Autoimmune Diseases / complications
  • Case-Control Studies
  • Cells, Cultured
  • Chaperonin 60 / metabolism
  • Endothelial Cells / enzymology*
  • Endothelial Cells / immunology
  • Endothelial Cells / metabolism
  • Female
  • Humans
  • Male
  • Middle Aged
  • Mitochondrial Proton-Translocating ATPases / immunology*
  • Mitochondrial Proton-Translocating ATPases / metabolism
  • Mitochondrial Proton-Translocating ATPases / physiology
  • Vasculitis / blood
  • Vasculitis / etiology*
  • Vasculitis / immunology
  • Vasculitis / metabolism
  • Young Adult

Substances

  • Antigens, Surface
  • Autoantibodies
  • Chaperonin 60
  • anti-endothelial cell antibody
  • Mitochondrial Proton-Translocating ATPases