Sertad1 is elevated and plays a necessary role in synaptic loss, neuron death and cognitive impairment in a model of Alzheimer’s disease

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Abstract
Dysfunctional autophagy is a primary characteristic of Alzheimer’s disease (AD) pathogenesis. How autophagic impairment leads to cellular changes that contributes to AD pathogenesis remains unclear. To study this further, we assessed levels of autophagy related proteins in 5xFAD mice brain at different ages and found their robust upregulation in cortex and hippocampus suggesting increased induction of autophagy with disease progression but failed clearance. We have identified a transcriptional coregulator Sertad1, as a key mediator of dysfunctional autophagy in AD mice. We found a progressive elevation in Sertad1 levels in 5xFAD mice with age compared to wild-type (WT) mice. Sertad1 knockdown in 5xFAD mice brain lowered levels of autophagy related proteins and lysosome marker, LAMP1 suggesting its role in autophagy flux modulation. FoxO3a is an important transcriptional regulator of the autophagy network and lies at the nexus of autophagy-apoptosis cross-talk. We found that Sertad1 knockdown blocked nuclear translocation of FoxO3a along with a restoration in Akt activity. Further, we showed that knockdown of Sertad1 in 5xFAD mice brain improved cognitive functions along with a remarkable restoration in synaptic health and dendritic spine density. Taken together, our results demonstrated that autophagy is robustly induced with disease progression but it is impaired; Sertad1 knockdown restored autophagy defects, synaptic loss and improved learning and memory in AD models. Thus, we propose that Sertad1 acts in a multimodal manner regulating crucial cell death pathways including apoptosis and autophagy and could be an excellent target for therapeutic intervention to combat a multifactorial disorder such as AD.

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