CR6-interacting factor 1 is a key regulator in Aβ-induced mitochondrial disruption and pathogenesis of Alzheimer's disease

Mitochondrial dysfunction, often characterized by massive fission and other morphological abnormalities, is a well-known risk factor for Alzheimer's disease (AD). One causative mechanism underlying AD-associated mitochondrial dysfunction is thought to be amyloid-beta (A beta), yet the pathways between A beta and mitochondrial dysfunction remain elusive. In this study, we report that CR6-interacting factor 1 (Crif1), a mitochondrial inner membrane protein, is a key player in A beta-induced mitochondrial dysfunction. Specifically, we found that Crif1 levels were downregulated in the pathological regions of Tg6799 mice brains, wherein overexpressed A beta undergoes self-aggregation. Downregulation of Crif1 was similarly observed in human AD brains as well as in SH-SY5Y cells treated with A beta. In addition, knockdown of Crif1, using RNA interference, induced mitochondrial dysfunction with phenotypes similar to those observed in A beta-treated cells. Conversely, Crif1 overexpression prevented A beta-induced mitochondrial dysfunction and cell death. Finally, we show that A beta-induced downregulation of Crif1 is mediated by enhanced reactive oxygen species (ROS) and ROS-dependent sumoylation of the transcription factor specificity protein 1 (Sp1). These results identify the ROS-Sp1-Crif1 pathway to be a new mechanism underlying A beta-induced mitochondrial dysfunction and suggest that ROS-mediated downregulation of Crif1 is a crucial event in AD pathology. We propose that Crif1 may serve as a novel therapeutic target in the treatment of AD.