APP Knockout Cell Line (HEK293)

BACKGROUND:Activating the ubiquitin-proteasome system to dismantle disease- related proteins such as tau, β-amyloid, APP, and α-synuclein is an important focus in the research of neurodegenerative proteinopathy. By analyzing the serum RNA extracted from wild-type and Alzheimer's disease (AD) transgenic mice at different ages (4, 8, and 12 months), this study revealed a new protective role of FBXL16 in AD, primarily through facilitating the degradation of disease-related proteins via the ubiquitin proteasome system. METHODS:Proteomic analysis were conducted using protein lysates from HEK293 cells overexpressing FBXL16 to identify potential interacting proteins that interact with FBXL16. Subsequent experiments demonstrated that FBXL16 promotes the proteasomal degradation of the APP protein, as evidenced by co-immunoprecipitation with MG132 and cycloheximide (CHX), immunohistochemistry (IHC) and immunocytochemistry (ICC). Memory and cognitive improvements were observed in 3×Tg AD mice through the use of a lentivirus-mediated approach to generate a brain-specific AD mouse model overexpressing FBXL16 via stereotaxic injection. Furthermore, a brain-specific conditional knockout (cko) FBXL16 mouse model was generated and employed to further confirm the functional role of FBXL 16 in AD via various behavioral tests including Morris water maze and Y-maze. RESULTS:The level of FBXL16 in the brains of transgenic APP/PSEN mice with AD decreased with age. Accelerated degradation of APP was observed when FBXL16 was overexpressed in the hippocampi of these AD mice via a lentivirus. This process led to notable improvements in cognitive impairments and reductions in neuroinflammation. Further studies using proteomics and bioinformatics techniques identified transcription factors and binding proteins associated with FBXL16, providing deeper insights into the potential role of FBXL16 in the regulation of AD. Finally, the in vivo effects of FBXL16 deficiency were further substantiated in cko mice, which overexpress Aβ but specifically lack FBXL16 in the brain region. CONCLUSIONS:These findings suggest that FBXL16 could be a new regulator of AD. These findings provide a foundation for further research into drug development and potential therapeutic strategies to combat other related neurodegenerative proteinopathies.

BACKGROUND:Neuropathological features of Alzheimer's disease are characterized by the deposition of amyloid-β (Aβ) plaques and impairments in synaptic activity and memory. However, we know little about the physiological role of amyloid-β protein precursor (AβPP) from which Aβ derives. OBJECTIVE:Evaluate APP deficiency induced alterations in neuronal electrical activity and mitochondrial protein expression. METHODS:Utilizing electrophysiological, biochemical, pharmacological, and behavioral tests, we revealed aberrant local field potential (LFP), extracellular neuronal firing and levels of mitochondrial proteins. RESULT:We show that APP knockout (APP-/-) leads to increased gamma oscillations in the medial prefrontal cortex (mPFC) at 1-2 months old, which can be restored by baclofen (Bac), a γ-aminobutyric acid type B receptor (GABABR) agonist. A higher dose and longer exposure time is required for Bac to suppress neuronal firing in APP-/- mice than in wild type animals, indicating enhanced GABABR mediated activity in the mPFC of APP-/- mice. In line with increased GABABR function, the glutamine synthetase inhibitor, L-methionine sulfonate, significantly increases GABABR levels in the mPFC of APP-/- mice and this is associated with a significantly lower incidence of death. The results suggest that APP-/- mice developed stronger GABABR mediated inhibition. Using HEK 293 as an expression system, we uncover that AβPP functions to suppress GABABR expression. Furthermore, APP-/- mice show abnormal expression of several mitochondrial proteins. CONCLUSION:APP deficiency leads to both abnormal network activity involving defected GABABR and mitochondrial dysfunction, suggesting critical role of AβPP in synaptic and network function.