NMNAT1 inhibits axon degeneration via blockade of SARM1-mediated NAD(+) depletion

Overexpression of the NAD(+) biosynthetic enzyme NMNAT1 leads to preservation of injured axons. While increased NAD(+) or decreased NMN levels are thought to be critical to this process, the mechanism(s) of this axon protection remain obscure. Using steady-state and flux analysis of NAD(+) metabolites in healthy and injured mouse dorsal root ganglion axons, we find that rather than altering NAD(+) synthesis, NMNAT1 instead blocks the injury-induced, SARM1-dependent NAD(+) consumption that is central to axon degeneration.