S- Nitrosylation of CRTC1 in Alzheimer's disease impairs CREB- dependent gene expression induced by neuronal activity

cAMP response element- binding protein (CREB)- regulated transcription coactivator 1 (CRTC1) plays an important role in synaptic plasticity, learning, and long- term memory formation through the regulation of neuronal activity- dependent gene expression, and CRTC1 dysregulation is implicated in Alzheimer's disease (AD). Here, we show that increased S- nitrosylation of CRTC1 (forming SNO- CRTC1), as seen in cell- based, animal- based, and human- induced pluripotent stem cell (hiPSC)- derived cerebrocortical neuron- based AD models, disrupts its binding with CREB and diminishes the activity- dependent gene expression mediated by the CRTC1/CREB pathway. We identified Cys216 of CRTC1 as the primary target of S- nitrosylation by nitric oxide (NO)- related species. Using CRISPR/Cas9 techniques, we mutated Cys216 to Ala in hiPSC- derived cerebrocortical neurons bearing one allele of the APPSwe mutation (AD-hiPSC neurons). Introduction of this nonnitrosylatable CRTC1 mutant rescued defects in AD-hiPSC neurons, including decreased neurite length and increased neuronal cell death. Additionally, expression of nonnitrosylatable CRTC1 in vivo in the hippocampus rescued synaptic plasticity in the form of long- term potentiation in 5XFAD mice. Taken together, these results demonstrate that formation of SNO-CRTC1 contributes to the pathogenesis of AD by attenuating the neuronal activity- dependent CREB transcriptional pathway, and suggests a therapeutic target for AD.