High Resolution Imaging Study of Interactions between the 37 kDa/67 kDa Laminin Receptor and APP, Beta-Secretase and Gamma-Secretase in Alzheimer's Disease

Abstract

Alzheimer's disease (AD) is the most prevalent form of dementia affecting the elderly. Neurodegeneration is caused by the amyloid beta (Aβ) peptide which is generated from the sequential proteolytic cleavage of the Amyloid Precursor Protein (APP) by the β– and γ- secretases. Previous reports revealed that the 37 kDa/67 kDa laminin receptor (LRP/LR) is involved in APP processing, however, the exact mechanism by which this occurs remains largely unclear. This study sought to assess whether LRP/LR interacted with APP, β- or γ-secretase. Detailed confocal microscopy revealed that LRP/LR showed a strong co-localisation with APP, β- and γ-secretase, respectively, at various sub-cellular locations. Superresolution Structured Illumination Microscopy (SR-SIM) showed that interactions were unlikely between LRP/LR and APP and β-secretase, respectively, while there was strong co-localisation between LRP/LR and γ-secretase at this 80 nm resolution. FRET was further employed to assess the possibility of protein-protein interactions and only an interaction between LRP/LR and γ-secretase was found. FLAG co-immunoprecipitation confirmed these findings as LRP/LR co-immunoprecipitated with γ-secretase, but failed to do so with APP. These findings indicate that LRP/LR exerts its influence on Aβ shedding via a direct interaction with the γ-secretase and possibly an indirect interaction with the β-secretase.

Fenofibrate reduces amyloidogenic processing of APP in APP/PS1 transgenic mice via PPAR‐α/PI3‐K pathway

“…The accumulation of extracellular amyloid‐β (Aβ) plaques and the formation of intracellular neurofibrillary tangles composed of hyperphosphorylated tau protein are the two hallmark features of AD (Jovanovic et al, 2014). Oligomeric Aβ is thought to be the candidate etiological agent of AD because it has been identified to induce neurotoxicity via interactions with many other proteins (Verdier and Penke, 2004; Kudo et al, 2012).…”

Novel patented therapeutic approaches targeting the 37/67 kDa laminin receptor for treatment of cancer and Alzheimer’s disease

“…As sAPPb levels were significantly reduced upon anti-LRP/LR antibody blockade and shRNA knockdown, an interaction between LRP/LR and b-secretase (the enzyme responsible for sAPPb cleavage from APP) seemed probable. Co-immunoprecipitation between these two proteins, as well as a strong degree of co-localisation further suggested the likelihood of this; however, high-resolution imaging (super resolution structured illumination [SR-SIM]) and FRET analysis revealed that a direct interaction between these two proteins did not exist [100]. Since BACE1 and LRP/LR share several interaction partners, namely PrP c [101] and heparan sulphate proteoglycans [102], the results obtained during co-immunoprecipitation suggest a possible indirect interaction between b-secretase and LRP/LR mediated by a cellular component that interacts with both proteins.…”

“…The co-localisation was seen predominantly in the cytoplasmic regions of the cells, where APP processing is known to occur within the endosomes, and on the cell surface from which Ab is shed. Upon FRET analysis, a strong signal was obtained suggesting that FRET had occurred between PS1 and LRP/ LR [100], indicating that the two proteins are within 10 nm of each other --a proximity that is close enough to warrant a direct interaction.…”

Anti-LRP/LR-specific antibody IgG1-iS18 impedes adhesion and invasion of pancreatic cancer and neuroblastoma cells

“…The receptor is seen to be overexpressed on the surface of tumorigenic cells such as cervical, lung, prostate and colon [9, 10], breast and oesophageal [11] and liver cancer cells [12], thus serving many physiological functions such as signal transduction, cell cycle progression, cell migration, cell-matrix adhesion, cell viability and proliferation [13–15]. LRP/LR is also associated with the process of Aβ- generation in Alzheimer’s disease [16, 17] as well as enhancing telomerase activity which is seen to play a role in disease progression and chemotherapy resistance in some cancers [18]. LRP/LR overexpression directly promotes the adhesion and invasion of tumorigenic cell lines via the process of metastasis.…”