Characterization of Cerebrospinal Fluid BACE1 Species
Por:
Lopez-Font I, Boix CP, Zetterberg H, Blennow K and Saez J
Publicada:
1 dic 2019
Resumen:
The beta-site amyloid precursor protein cleaving enzyme 1 (BACE1) is the main brain beta-secretase responsible for the amyloidogenic processing of the amyloid precursor protein (APP). Previous studies have suggested that cerebrospinal fluid (CSF) beta-secretase activity may be a candidate diagnostic biomarker for Alzheimer's disease (AD), but biochemical characterization of BACE1 protein in CSF is needed. CSF samples from 19 AD patients and 19 age-matched non-AD controls (n = 19) were classified according to their A beta 42, total tau, and P-tau CSF biomarker levels. We found that beta-secretase activity was higher in the CSF of AD subjects than in that of the controls. We found that the majority of the beta-secretase activity in the CSF, measured using a peptide substrate homologous to the BACE1 cleavage site, was not inhibited by specific BACE1 inhibitors. We defined enzymatic activity attributable specifically to BACE1 as the activity that was blocked by the specific inhibitors, which is still higher in AD subjects. BACE1 protein levels were characterized by lectin binding, immunoprecipitation, blue native-PAGE, and western blotting using antibodies against specific protein domains. BACE1 was found to be present in human CSF as a mature form of similar to 70 kDa that probably comprised truncated and full-length species, and also as an immature form of similar to 50 kDa that retains the prodomain. CSF-BACE1 was found to assemble into hetero-complexes containing distinct species. Immunoblotting with an antibody against the C-terminus of BACE1 revealed significantly higher levels of the 70-kDa full-length BACE1, while the 50 kDa immature form remained unaltered. When the 70-kDa species was probed with an antibody against the N-terminus of BACE1 (which does not discriminate between truncated and full-length forms), no increase in immunoreactivity was observed, suggesting that truncated forms of BACE1 do not increase in AD. In conclusion, the complexity of BACE1 species in CSF has to be taken into consideration when determining BACE1 activity and protein levels in CSF as biomarkers of AD.
Filiaciones:
:
Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, Av. Ramón y Cajal s/n, E-03550, Sant Joan d'Alacant, Spain.
Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Sant Joan d'Alacant, Spain.
Boix CP:
Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, Av. Ramón y Cajal s/n, E-03550, Sant Joan d'Alacant, Spain
Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Sant Joan d'Alacant, Spain
Zetterberg H:
Clinical Neurochemistry Laboratory, Sahlgrenska University Hospital, Mölndal, Sweden
Department of Neuroscience and Physiology, the Sahlgrenska Academy at the University of Gothenburg, Mölndal, Sweden
Department of Neurodegenerative Disease, UCL Institute of Neurology, Queen Square, London, UK
UK Dementia Research Institute at UCL, London, UK
Blennow K:
Clinical Neurochemistry Laboratory, Sahlgrenska University Hospital, Mölndal, Sweden
Department of Neuroscience and Physiology, the Sahlgrenska Academy at the University of Gothenburg, Mölndal, Sweden
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