Abstract
Nicotinamide adenine dinucleotide (NAD(+)) is an endogenous enzyme cofactor and cosubstrate that has effects on diverse cellular and physiologic processes, including reactive oxygen species generation, mitochondrial function, apoptosis, and axonal degeneration. A major goal is to identify the NAD(+)-regulated cellular pathways that may mediate these effects. Here we show that the dynamic assembly and disassembly of microtubules is markedly altered by NAD(+). Furthermore, we show that the disassembly of microtubule polymers elicited by microtubule depolymerizing agents is blocked by increasing intracellular NAD(+) levels. We find that these effects of NAD(+) are mediated by the activation of the mitochondrial sirtuin sirtuin-3 (SIRT3). Overexpression of SIRT3 prevents microtubule disassembly and apoptosis elicited by antimicrotubule agents and knockdown of SIRT3 prevents the protective effects of NAD(+) on microtubule polymers. Taken together, these data demonstrate that NAD(+) and SIRT3 regulate microtubule polymerization and the efficacy of antimicrotubule agents.