NAD depletion mediates cytotoxicity in human neurons with autophagy deficiency

Cell Rep. 2023 May 30;42(5):112372. doi: 10.1016/j.celrep.2023.112372. Epub 2023 Apr 21.

Abstract

Autophagy is a homeostatic process critical for cellular survival, and its malfunction is implicated in human diseases including neurodegeneration. Loss of autophagy contributes to cytotoxicity and tissue degeneration, but the mechanistic understanding of this phenomenon remains elusive. Here, we generated autophagy-deficient (ATG5-/-) human embryonic stem cells (hESCs), from which we established a human neuronal platform to investigate how loss of autophagy affects neuronal survival. ATG5-/- neurons exhibit basal cytotoxicity accompanied by metabolic defects. Depletion of nicotinamide adenine dinucleotide (NAD) due to hyperactivation of NAD-consuming enzymes is found to trigger cell death via mitochondrial depolarization in ATG5-/- neurons. Boosting intracellular NAD levels improves cell viability by restoring mitochondrial bioenergetics and proteostasis in ATG5-/- neurons. Our findings elucidate a mechanistic link between autophagy deficiency and neuronal cell death that can be targeted for therapeutic interventions in neurodegenerative and lysosomal storage diseases associated with autophagic defect.

Keywords: CP: Cell biology; CP: Metabolism; NAD; NADases; NAM; NMN; NR; autophagy; cell death; cell survival, human embryonic stem cell-derived neurons; mitochondria; nicotinamide; nicotinamide adenine dinucleotide; nicotinamide mononucleotide; nicotinamide riboside.

Publication types

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

MeSH terms

  • Autophagy
  • Humans
  • Mitochondria / metabolism
  • NAD* / metabolism
  • Neurons / metabolism
  • Niacinamide / metabolism
  • Nicotinamide Mononucleotide* / metabolism

Substances

  • NAD
  • Nicotinamide Mononucleotide
  • Niacinamide