Quinolinate phosphoribosyl transferase, a key enzyme in de novo NAD(+) synthesis, suppresses spontaneous cell death by inhibiting overproduction of active-caspase-3.
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.
Ishidoh
Kazumi
K
Division of Molecular Biology, Institute for Health Sciences, Tokushima Bunri University, Tokushima, Japan. kishidoh@tokushima.bunri-u.ac.jp
Kamemura
Norio
N
Imagawa
Takahito
T
Oda
Masataka
M
Sakurai
Jun
J
Katunuma
Nobuhiko
N
D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D061945:Caspase Inhibitors; D002417:Cattle; D002470:Cell Survival; D002478:Cells, Cultured; D003593:Cytoplasm / Q000378:metabolism; D003609:Dactinomycin / Q000494:pharmacology; D004789:Enzyme Activation; D006367:HeLa Cells / Q000201:enzymology; D006801:Humans; D007124:Immunoenzyme Techniques; D047468:Immunoprecipitation; D008099:Liver / Q000378:metabolism; D008969:Molecular Sequence Data; D009243:NAD / Q000378:metabolism*; D010430:Pentosyltransferases / Q000502:physiology*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D000098553:Nicotinate-Nucleotide Diphosphorylase (Carboxylating)
D061945:Caspase Inhibitors; D011994:Recombinant Proteins; D009243:NAD; D003609:Dactinomycin; D010430:Pentosyltransferases; D000098553:Nicotinate-Nucleotide Diphosphorylase (Carboxylating)