Deficiency of the INCL protein Ppt1 results in changes in ectopic F1-ATP synthase and altered cholesterol metabolism

Hum Mol Genet. 2008 May 15;17(10):1406-17. doi: 10.1093/hmg/ddn028. Epub 2008 Feb 1.

Abstract

Infantile neuronal ceroid lipofuscinosis (INCL) is a severe neurodegenerative disease caused by deficiency of palmitoyl protein thioesterase 1 (PPT1). INCL results in dramatic loss of thalamocortical neurons, but the disease mechanism has remained elusive. In the present work we describe the first interaction partner of PPT1, the F(1)-complex of the mitochondrial ATP synthase, by co-purification and in vitro-binding assays. In addition to mitochondria, subunits of F(1)-complex have been reported to localize in the plasma membrane, and to be capable of acting as receptors for various ligands such as apolipoprotein A-1. We verified here the plasma membrane localization of F(1)-subunits on mouse primary neurons and fibroblasts by cell surface biotinylation and TIRF-microscopy. To gain further insight into the Ppt1-mediated properties of the F(1)-complex, we utilized the Ppt1-deficient Ppt1(Delta ex4) mice. While no changes in the mitochondrial function could be detected in the brain of the Ppt1(Delta ex4) mice, the levels of F(1)-subunits alpha and beta on the plasma membrane were specifically increased in the Ppt1(Delta ex4) neurons. Significant changes were also detected in the apolipoprotein A-I uptake by the Ppt1(Delta ex4) neurons and the serum lipid composition in the Ppt1(Delta ex4) mice. These data indicate neuron-specific changes for F(1)-complex in the Ppt1-deficient cells and give clues for a possible link between lipid metabolism and neurodegeneration in INCL.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apolipoprotein A-I / blood
  • Apolipoprotein A-I / metabolism
  • Brain / abnormalities
  • Brain / metabolism
  • Brain / pathology
  • Brain / physiopathology
  • Cell Membrane / metabolism
  • Cholesterol / blood
  • Cholesterol / metabolism*
  • Electron Transport Complex II / metabolism
  • Female
  • Humans
  • Lipid Metabolism
  • Lipids / blood
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Mitochondria / enzymology
  • Mitochondria / metabolism
  • Neuroglia / metabolism
  • Neuronal Ceroid-Lipofuscinoses / metabolism*
  • Neurons / cytology
  • Neurons / metabolism
  • Protein Subunits / analysis
  • Protein Subunits / metabolism
  • Proton-Translocating ATPases / analysis
  • Proton-Translocating ATPases / metabolism*
  • Thiolester Hydrolases / blood
  • Thiolester Hydrolases / genetics*
  • Thiolester Hydrolases / isolation & purification
  • Thiolester Hydrolases / metabolism*

Substances

  • Apolipoprotein A-I
  • Lipids
  • Protein Subunits
  • respiratory complex II
  • Cholesterol
  • Electron Transport Complex II
  • Thiolester Hydrolases
  • palmitoyl-protein thioesterase
  • Proton-Translocating ATPases