Quinolinate phosphoribosyl transferase, a key enzyme in de novo NAD(+) synthesis, suppresses spontaneous cell death by inhibiting overproduction of active-caspase-3

Biochim Biophys Acta. 2010 May;1803(5):527-33. doi: 10.1016/j.bbamcr.2010.02.007. Epub 2010 Mar 3.

Abstract

Quinolinate phosphoribosyl transferase (QPRT) is a key enzyme in de novo NAD(+) synthesis. QPRT enzyme activity has a restricted tissue distribution, although QPRT mRNA is expressed ubiquitously. This study was designed to elucidate the functions of QPRT protein in addition to NAD(+) synthesis. QPRT was identified as a caspase-3 binding protein using double layer fluorescent zymography, but was not a substrate for caspase-3. Surface plasmon resonance analysis using recombinant proteins showed interaction of QPRT with active-caspase-3 in a dose dependent manner at 55 nM of the dissociation constant. The interaction was also confirmed by immunoprecipitation analysis of actinomycin D-treated QPRT-FLAG expressing cells using anti-FLAG-agarose. QPRT-depleted cells showed increased sensitivity to spontaneous cell death, upregulated caspase-3 activity and strong active-caspase-3 signals. Considered together, the results suggested that QPRT protein acts as an inhibitor of spontaneous cell death by suppressing overproduction of active-caspase-3.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Apoptosis*
  • Blotting, Western
  • Caspase Inhibitors*
  • Cattle
  • Cell Survival
  • Cells, Cultured
  • Cytoplasm / metabolism
  • Dactinomycin / pharmacology
  • Enzyme Activation
  • HeLa Cells / enzymology
  • Humans
  • Immunoenzyme Techniques
  • Immunoprecipitation
  • Liver / metabolism
  • Molecular Sequence Data
  • NAD / metabolism*
  • Pentosyltransferases / physiology*
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism

Substances

  • Caspase Inhibitors
  • Recombinant Proteins
  • NAD
  • Dactinomycin
  • Pentosyltransferases
  • nicotinate-nucleotide diphosphorylase (carboxylating)