NAD + restores proteostasis through splicing-dependent autophagy

Autophagy preserves neuronal integrity by clearing damaged proteins and organelles, but its efficiency declines with aging and neurodegeneration. Depletion of the oxidized form of nicotinamide adenine dinucleotide (NAD⁺) is a hallmark of this decline, yet how metabolic restoration enhances autophagic control has remained obscure. Meanwhile, alternative RNA splicing errors accumulate in aging brains, compromising proteostasis. Here, we identify a metabolic - transcriptional mechanism linking NAD⁺ metabolism to autophagic proteostasis through the NAD⁺ -EVA1C axis. Cross-species analyses in C. elegans, mice, and human samples reveal that NAD⁺ supplementation corrects hundreds of age- or Alzheimer-associated splicing errors, notably restoring balanced expression of EVA1C isoforms. Loss of EVA1C impairs the memory and proteostatic benefits of NAD⁺, underscoring its essential role in neuronal resilience. Mechanistically, NAD⁺ rebalances EVA1C isoforms that interact with chaperones BAG1 and HSPA/HSP70, reinforcing their network to facilitate chaperone-assisted selective macroautophagy and proteasomal degradation of misfolded proteins such as MAPT/tau. Thus, NAD⁺ restoration coordinates RNA splicing fidelity with downstream proteostatic systems, establishing a metabolic - transcriptional checkpoint for neuronal quality control. This finding expands the paradigm of autophagy regulation, positioning metabolic splice-switching as a crucial mechanism to maintain proteostasis and suggesting new strategies to combat aging-related neurodegenerative diseases.