These mitochondrial changes were abolished by treatment with -site APP-cleaving enzyme inhibitor IV. of dynamin-like protein 1 and OPA1 were significantly decreased whereas levels of Fis1 were significantly improved in APPwt and APPswe M17 cells. Notably, overexpression of dynamin-like protein 1 in these cells rescued the irregular mitochondrial distribution and differentiation deficiency, but failed to save mitochondrial fragmentation and practical guidelines, whereas overexpression of OPA1 rescued mitochondrial fragmentation and practical parameters, but failed to restore normal mitochondrial distribution. Overexpression of APP or A-derived diffusible ligand treatment also led SAR7334 to mitochondrial fragmentation and reduced mitochondrial protection in neuronal processes in differentiated main hippocampal neurons. Based on these data, we concluded that APP, through amyloid production, causes an imbalance of mitochondrial fission/fusion that results in mitochondrial fragmentation and irregular distribution, which contributes to mitochondrial and neuronal dysfunction. Keywords:amyloid precursor protein, DLP1, mitochondrial fragmentation, OPA1, perinuclear build up Alzheimer disease (AD) is the most common neurodegenerative disorder in the aged human population and is characterized by considerable regionalized neuronal loss and the presence of neurofibrillary tangles and senile plaques in the brain. Senile plaques are deposits of amyloid- (A), a 3943-aa peptide produced by the sequential cleavage of – and -secretase in the C terminus of amyloid precursor protein (APP) (1). More than 20 mutations in APP have been linked to familial AD (fAD) that have modified APP processing with respect to enhanced A generation or aggregation (2). Despite rigorous focus Rabbit polyclonal to PEX14 on APP and A, the exact mechanisms responsible for the massive neurodegeneration in early-stage fAD are incompletely resolved. Persuasive evidence suggests that oxidative stress is one of the earliest changes and takes on an important part in the pathological process in AD (3). Improved oxidative stress levels have been found in the brains of individuals with fAD in Sweden and early in Tg2576 APP transgenic mice (4,5), suggesting that fAD-associated mutations probably enhance oxidative stress. Mitochondria are the major source of reactive SAR7334 oxygen varieties (ROS) and, in fact, mitochondrial dysfunction, as well as hypometabolism, have long been implicated in the onset of the familial and sporadic forms of AD (6). mtDNA problems have also been linked to an increased incidence of AD (7,8). Quantitative morphometric analysis of mitochondria shows improved irregular and damaged mitochondria in AD (9,10). Multiple lines of evidence support APP and A as contributing factors to mitochondrial dysfunction in AD: both APP and A are present in mitochondrial membrane and interact with mitochondrial proteins, block mitochondrial import channels, impair mitochondrial transport, disrupt the electron transfer chain, increase ROS levels, and cause mitochondrial damage (1115). A number of recent studies shown that mitochondria are dynamic organelles undergoing continual fission and fusion (16). In mammalian cells, fission requires Fis1 SAR7334 and dynamin-like protein (DLP1). Conversely, fusion entails OPA1, Mfn1, and Mfn2 (17). Unbalanced fusion prospects to mitochondrial elongation SAR7334 and unbalanced fission prospects to excessive mitochondrial fragmentation, both of which impair mitochondrial function (18,19). Impairments in mitochondrial dynamics are becoming progressively implicated in neurodegenerative diseases (16). Very recently, we reported irregular mitochondrial fission and fusion in AD fibroblasts (20). In this study, we targeted to determine whether APP and A cause mitochondrial dysfunction and neuronal dysfunction through modulation of mitochondrial dynamics. == Results == == Generation of SAR7334 Stable M17 Cell Lines Overexpressing APP. == To investigate the effects of APP overexpression on mitochondrial dynamics in neuronal cells, three self-employed clones of M17 cells stably transfected with WT APP cDNA (APPwt M17 cells) or APP Swedish mutant cDNA (APPswe M17 cells) were founded. Overexpression of APP in these lines was confirmedby Western blotting (Fig. 1A). There was no increase in basal cell death in any of these cell lines compared with control cells.