Evidence for a novel neuronal mechanism driving Alzheimer's disease, upstream of amyloid.

This perspective offers an alternative to the amyloid hypothesis in the etiology of Alzheimer's disease (AD). We review evidence for a novel signaling mechanism based on a little-known peptide, T14. T14 could drive neurodegeneration as an aberrantly activated process of plasticity selective to interconnecting subcortical nuclei, the isodendritic core, where cell loss starts at the pre-symptomatic stages of the disease. Each of these cell groups has the capacity to form T14, which can stimulate production of p-Tau and ß-amyloid, suggestive of an upstream driver of neurodegeneration. Moreover, results in an animal AD model show that antagonism of T14 with a cyclated variant, NBP14, prevents formation of ß-amyloid, and restores cognitive function to that of wild-type counterparts. Any diagnostic and/or therapeutic strategy based on T14-NBP14 awaits validation in clinical trials. However, an understanding of this novel signaling system could bring much-needed fresh insights into the progression of cell loss underlying AD. HIGHLIGHTS: The possible primary mechanism of neurodegeneration upstream of amyloid. Primary involvement of selectively vulnerable subcortical nuclei, isodendritic core. Bioactive peptide T14 trophic in development but toxic in context of mature brain. Potential for early-stage biomarker to detect Alzheimer's disease. Effective therapeutic halting neurodegeneration, validated already in 5XFAD mice.

Validity of CSF alpha-synuclein to predict psychosis in prodromal Alzheimer's disease.

Background: Alzheimer's disease (AD) accompanied by psychotic symptoms (PS) has a poor prognosis and may be associated with imbalances in key neural proteins such as alpha-synuclein (AS). Aim: The aim of the study was to evaluate the diagnostic validity of AS levels in the cerebrospinal fluid (CSF) as a predictor of the emergence of PS in patients with prodromal AD. Materials and methods: Patients with mild cognitive impairment were recruited between 2010 and 2018. Core AD biomarkers and AS levels were measured in CSF obtained during the prodromal phase of the illness. All patients who met the NIA-AA 2018 criteria for AD biomarkers received treatment with anticholinesterasic drugs. Follow-up evaluations were conducted to assess patients for the presence of psychosis using current criteria; the use of neuroleptic drugs was required for inclusion in the psychosis group. Several comparisons were made, taking into account the timing of the emergence of PS. Results: A total of 130 patients with prodromal AD were included in this study. Of these, 50 (38.4%) met the criteria for PS within an 8-year follow-up period. AS was found to be a valuable CSF biomarker to differentiate between the psychotic and non-psychotic groups in every comparison made, depending on the onset of PS. Using an AS level of 1,257 pg/mL as the cutoff, this predictor achieved at least 80% sensitivity. Conclusion: To our knowledge, this study represents the first time that a CSF biomarker has shown diagnostic validity for prediction of the emergence of PS in patients with prodromal AD.

ADAM10 Gene Variants in AD Patients and Their Relationship to CSF Protein Levels.

ADAM10 is the main α-secretase acting in the non-amyloidogenic processing of APP. We hypothesized that certain rare ADAM10 variants could increase the risk for AD by conferring the age-related downregulation of α-secretase. The ADAM10 gene was sequenced in 103 AD cases (82% familial) and 96 cognitively preserved nonagenarians. We examined rare variants (MAF < 0.01) and determined their potential association in the AD group with lower CSF protein levels, as analyzed by means of ELISA, and Western blot (species of 50 kDa, 55 kDa, and 80 kDa). Rare variants were found in 15.5% of AD cases (23% early-onset, 8% late-onset) and in 12.5% of nonagenarians, and some were group-specific. All were intronic variants except Q170H, found in three AD cases and one nonagenarian. The 3'UTR rs74016945 (MAF = 0.01) was found in 6% of the nonagenarians (OR 0.146, p = 0.057). Altogether, ADAM10 total levels or specific species were not significantly different when comparing AD with controls or carriers of rare variants versus non-carriers (except a Q170H carrier exhibiting low levels of all species), and did not differ according to the age at onset or APOE genotype. We conclude that ADAM10 exonic variants are uncommon in AD cases, and the presence of rare intronic variants (more frequent in early-onset cases) is not associated with decreased protein levels in CSF.

Transient Changes in the Plasma of Astrocytic and Neuronal Injury Biomarkers in COVID-19 Patients without Neurological Syndromes.

The levels of several glial and neuronal plasma biomarkers have been found to increase during the acute phase in COVID-19 patients with neurological symptoms. However, replications in patients with minor or non-neurological symptoms are needed to understand their potential as indicators of CNS injury or vulnerability. Plasma levels of glial fibrillary acidic protein (GFAP), neurofilament light chain protein (NfL), and total Tau (T-tau) were determined by Single molecule array (Simoa) immunoassays in 45 samples from COVID-19 patients in the acute phase of infection [moderate (n = 35), or severe (n = 10)] with minor or non-neurological symptoms; in 26 samples from fully recovered patients after ~2 months of clinical follow-up [moderate (n = 23), or severe (n = 3)]; and in 14 non-infected controls. Plasma levels of the SARS-CoV-2 receptor, angiotensin-converting enzyme 2 (ACE2), were also determined by Western blot. Patients with COVID-19 without substantial neurological symptoms had significantly higher plasma concentrations of GFAP, a marker of astrocytic activation/injury, and of NfL and T-tau, markers of axonal damage and neuronal degeneration, compared with controls. All these biomarkers were correlated in COVID-19 patients at the acute phase. Plasma GFAP, NfL and T-tau levels were all normalized after recovery. Recovery was also observed in the return to normal values of the quotient between the ACE2 fragment and circulating full-length species, following the change noticed in the acute phase of infection. None of these biomarkers displayed differences in plasma samples at the acute phase or recovery when the COVID-19 subjects were sub-grouped according to occurrence of minor symptoms at re-evaluation 3 months after the acute episode (so called post-COVID or "long COVID"), such as asthenia, myalgia/arthralgia, anosmia/ageusia, vision impairment, headache or memory loss. Our study demonstrated altered plasma GFAP, NfL and T-tau levels in COVID-19 patients without substantial neurological manifestation at the acute phase of the disease, providing a suitable indication of CNS vulnerability; but these biomarkers fail to predict the occurrence of delayed minor neurological symptoms.

Presenilin 1 Modulates Acetylcholinesterase Trafficking and Maturation.

In Alzheimer's disease (AD), the reduction in acetylcholinesterase (AChE) enzymatic activity is not paralleled with changes in its protein levels, suggesting the presence of a considerable enzymatically inactive pool in the brain. In the present study, we validated previous findings, and, since inactive forms could result from post-translational modifications, we analyzed the glycosylation of AChE by lectin binding in brain samples from sporadic and familial AD (sAD and fAD). Most of the enzymatically active AChE was bound to lectins Canavalia ensiformis (Con A) and Lens culinaris agglutinin (LCA) that recognize terminal mannoses, whereas Western blot assays showed a very low percentage of AChE protein being recognized by the lectin. This indicates that active and inactive forms of AChE vary in their glycosylation pattern, particularly in the presence of terminal mannoses in active ones. Moreover, sAD subjects showed reduced binding to terminal mannoses compared to non-demented controls, while, for fAD patients that carry mutations in the PSEN1 gene, the binding was higher. The role of presenilin-1 (PS1) in modulating AChE glycosylation was then studied in a cellular model that overexpresses PS1 (CHO-PS1). In CHO-PS1 cells, binding to LCA indicates that AChE displays more terminal mannoses in oligosaccharides with a fucosylated core. Immunocytochemical assays also demonstrated increased presence of AChE in the trans-Golgi. Moreover, AChE enzymatic activity was higher in plasmatic membrane of CHO-PS1 cells. Thus, our results indicate that PS1 modulates trafficking and maturation of AChE in Golgi regions favoring the presence of active forms in the membrane.

Serum angiotensin-converting enzyme 2 as a potential biomarker for SARS-CoV-2 infection and vaccine efficacy.

Various species of the SARS-CoV-2 host cell receptor, the angiotensin-converting enzyme 2 (ACE2), are present in serum, which may result from virus entry and subsequent proteolytic processing of the membrane receptor. We have recently demonstrated changes of particular ACE2 species in virus infected humans, either cleaved fragments or circulating full-length species. Here, we further explore the potential of serum ACE2 as a biomarker to test SARS-CoV-2 infection and vaccine efficacy in virus susceptible transgenic K18-hACE2 mice expressing human ACE2. First, in serum samples derived from K18-hACE2 mice challenged with a lethal dose of SARS-CoV-2, we observed an increase in the levels of cleaved ACE2 fragment at day 2 post-challenge, which may represent the subsequent proteolytic processing through virus entry. These elevated levels were maintained until the death of the animals at day 6 post-challenge. The circulating full-length ACE2 form displayed a sizable peak at day 4, which declined at day 6 post-challenge. Noticeably, immunization with two doses of the MVA-CoV2-S vaccine candidate prevented ACE2 cleaved changes in serum of animals challenged with a lethal dose of SARS-CoV-2. The efficacy of the MVA-CoV2-S was extended to vaccinated mice after virus re-challenge. These findings highlight that ACE2 could be a potential serum biomarker for disease progression and vaccination against SARS-CoV-2.

Proceedings of workshop: "Neuroglycoproteins in health and disease", INNOGLY cost action.

The Cost Action "Innovation with glycans: new frontiers from synthesis to new biological targets" (INNOGLY) hosted the Workshop "Neuroglycoproteins in health and disease", in Alicante, Spain, on March 2022. This event brought together an european group of scientists that presented novel insights into changes in glycosylation in diseases of the central nervous system and cancer, as well as new techniques to study protein glycosylation. Herein we provide the abstracts of all the presentations.

Relation between Alpha-Synuclein and Core CSF Biomarkers of Alzheimer's Disease.

Background: Alzheimer's disease (AD) is characterized by the presence of ß-amyloid plaques and neurofibrillary tangles, while Lewy body dementia (LBD) is characterized by α-synuclein (α-syn) inclusions. Some authors examine α-syn protein in the neurodegeneration process of AD and propose to consider cerebrospinal fluid (CSF) α-syn as a possible additional biomarker to the so-called "core" of AD. Objective: To determine whether there is a correlation between α-syn levels and "core" AD biomarkers in patients with mild cognitive impairment (MCI). Materials and methods: In total, 81 patients in the early stages of MCI were selected from the outpatient dementia consultation in Alicante General Hospital. Using a cross-sectional case-control design, patients were analyzed in four groups: stable MCI (MCIs; n = 25), MCI due to AD (MCI-AD; n = 32), MCI due to LBD (MCI-LBD; n = 24) and a control group of patients with acute or chronic headache (Ctrl; n = 18). Correlation between CSF protein levels in the different groups was assessed by the Rho Spearman test. Results: We found positive correlations between T-tau protein and α-syn (ρ = 0.418; p value < 0.05) and p-tau181p and α-syn (ρ = 0.571; p value < 0.05) exclusively in the MCI-AD group. Conclusion: The correlation found between α-syn and tau proteins in the first stages of AD support the involvement of α-syn in the pathogenesis of AD. This result may have clinical and diagnostic implications, as well as help to apply the new concept of "precision medicine" in patients with MCI.

Plasma ACE2 species are differentially altered in COVID-19 patients.

Studies are needed to identify useful biomarkers to assess the severity and prognosis of COVID-19 disease, caused by severe acute respiratory syndrome coronavirus (SARS-CoV-2) virus. Here, we examine the levels of various plasma species of the SARS-CoV-2 host receptor, the angiotensin-converting enzyme 2 (ACE2), in patients at different phases of the infection. Human plasma ACE2 species were characterized by immunoprecipitation and western blotting employing antibodies against the ectodomain and the C-terminal domain, using a recombinant human ACE2 protein as control. In addition, changes in the cleaved and full-length ACE2 species were also examined in serum samples derived from humanized K18-hACE2 mice challenged with a lethal dose of SARS-CoV-2. ACE2 immunoreactivity was present in human plasma as several molecular mass species that probably comprise truncated (70 and 75 kDa) and full-length forms (95, 100, 130, and 170 kDa). COVID-19 patients in the acute phase of infection (n = 46) had significantly decreased levels of ACE2 full-length species, while a truncated 70-kDa form was marginally higher compared with non-disease controls (n = 26). Levels of ACE2 full-length species were in the normal range in patients after a recovery period with an interval of 58-70 days (n = 29), while the 70-kDa species decreased. Levels of the truncated ACE2 species served to discriminate between individuals infected by SARS-CoV-2 and those infected with influenza A virus (n = 17). In conclusion, specific plasma ACE2 species are altered in patients with COVID-19 and these changes normalize during the recovery phase. Alterations in ACE2 species following SARS-CoV-2 infection warrant further investigation regarding their potential usefulness as biomarkers for the disease process and to asses efficacy during vaccination.

Tau phosphorylation by glycogen synthase kinase 3ß modulates enzyme acetylcholinesterase expression.

In Alzheimer's disease (AD), the enzyme acetylcholinesterase (AChE) co-localizes with hyperphosphorylated tau (P-tau) within neurofibrillary tangles. Having demonstrated that AChE expression is increased in the transgenic mouse model of tau Tg-VLW, here we examined whether modulating phosphorylated tau levels by over-expressing wild-type human tau and glycogen synthase kinase-3ß (GSK3ß) influences AChE expression. In SH-SY5Y neuroblastoma cells expressing higher levels of P-tau, AChE activity and protein increased by (20% ± 2%) and (440% ± 150%), respectively. Western blots and qPCR assays showed that this increment mostly corresponded to the cholinergic ACHE-T variant, for which the protein and transcript levels increased ~60% and ~23%, respectively. Moreover, in SH-SY5Y cells differentiated into neurons by exposure to retinoic acid (10 µM), over-expression of GSK3ß and tau provokes an imbalance in cholinergic activity with a decrease in the neurotransmitter acetylcholine in the cell (45 ± 10%). Finally, we obtained cerebrospinal fluid (CSF) from AD patients enrolled on a clinical trial of tideglusib, an irreversible GSK3ß inhibitor. In CSF of patients that received a placebo, there was an increase in AChE activity (35 ± 16%) respect to basal levels, probably because of their treatment with AChE inhibitors. However, this increase was not observed in tideglusib-treated patients. Moreover, CSF levels of P-tau at the beginning measured by commercially ELISA kits correlated with AChE activity. In conclusion, this study shows that P-tau can modulate AChE expression and it suggests that AChE may possibly increase in the initial phases of AD.

α-Secretase nonsense mutation (ADAM10 Tyr167*) in familial Alzheimer's disease.

BACKGROUND: The disintegrin metalloproteinase 10 (ADAM10) is the main α-secretase acting in the non-amyloidogenic processing of APP. Some ADAM10 gene variants have been associated with higher susceptibility to develop late-onset AD, though clear clinical-genetic correlates remain elusive. METHODS: Clinical-genetic and biomarker study of a first family with early- and late-onset AD associated with a nonsense ADAM10 mutation (p.Tyr167*). CSF analysis included AD core biomarkers, as well as Western blot of ADAM10 species and sAPPα and sAPPß peptides. We evaluate variant's pathogenicity, pattern of segregation, and further screened for the p.Tyr167* mutation in 197 familial AD cases from the same cohort, 200 controls from the same background, and 274 AD cases from an independent Spanish cohort. RESULTS: The mutation was absent from public databases and segregated with the disease. CSF Aß42, total tau, and phosphorylated tau of affected siblings were consistent with AD. The predicted haploinsufficiency effect of the nonsense mutation was supported by (a) ADAM10 isoforms in CSF decreased around 50% and (b) 70% reduction of CSF sAPPα peptide, both compared to controls, while sAPPß levels remained unchanged. Interestingly, sporadic AD cases had a similar decrease in CSF ADAM10 levels to that of mutants, though their sAPPα and sAPPß levels resembled those of controls. Therefore, a decreased sAPPα/sAPPß ratio was an exclusive feature of mutant ADAM10 siblings. The p.Tyr167* mutation was not found in any of the other AD cases or controls screened. CONCLUSIONS: This family illustrates the role of ADAM10 in the amyloidogenic process and the clinical development of the disease. Similarities between clinical and biomarker findings suggest that this family could represent a genetic model for sporadic late-onset AD due to age-related downregulation of α-secretase. This report encourages future research on ADAM10 enhancers.

Pre-analytical stability of novel cerebrospinal fluid biomarkers.

Stability of the cerebrospinal fluid (CSF) composition under different pre-analytical conditions is relevant for the diagnostic potential of biomarkers. Our aim was to examine the pre-analytical stability of promising CSF biomarkers that are currently evaluated for their discriminative use in various neurological diseases. Pooled CSF was aliquoted and experimentally exposed to delayed storage: 0, 1, 2, 4, 24, 72, or 168 h at 4 °C or room temperature (RT), or 1-4 months at -20 °C; or up to 7 freeze/thaw (f/t) cycles, before final storage at -80 °C. Eleven CSF biomarkers were screened using immunoassays, liquid chromatography, or enzymatic methods. Levels of neurogranin (truncP75), chitinase-3-like protein (YKL-40), beta-site amyloid precursor protein cleaving enzyme 1 (BACE1), acetylcholinesterase (AChE) enzymatic activity, theobromine, secreted protein acidic and rich in cysteine-like 1 (SPARCL-1) and homovanillic acid (HVA) levels were not affected by the applied storage conditions. 3-Methoxy-4-hydroxyphenylglycol (MHPG) levels linearly and strongly decreased after 4 h at RT (-10%) or 24 h at 4 °C (-27%), and with 6% after every f/t cycle. 5-Methyltetrahydrofolate (5-MTHF) (-29% after 1 week at RT) and 5-hydroxyindoleacetic acid levels (5-HIAA) (-16% after 1 week at RT) were reduced and 3,4-dihydroxyphenylacetic acid (DOPAC) levels (+22% after 1 week at RT) increased, but only after >24 h at RT. Ten out of eleven potential CSF novel biomarkers showed very limited change under common storage and f/t conditions, suggesting that these CSF biomarkers can be trustfully tested under the pre-analytical conditions present across different cohorts.

Measurement of CSF α-synuclein improves early differential diagnosis of mild cognitive impairment due to Alzheimer's disease.

Previous studies have indicated the potential of cerebrospinal fluid (CSF) α-synuclein (α-syn) to be an additional biomarker for improving differential diagnosis of Alzheimer's disease (AD). We evaluated α-syn diagnostic performance across a well-characterized patient cohort with long-term follow-up. For this purpose, CSF α-syn levels were determined in 25 subjects diagnosed with stable mild cognitive impairment (stable MCI; n = 25), 27 MCI cases due to AD (MCI-AD; n = 32), 24 MCI cases due to Lewy body disease (MCI-LBD; n = 24) and control subjects (Ctrl; n = 18). CSF α-syn levels discriminate between the four groups. There were higher α-syn levels in MCI-AD patients and lower levels in MCI-LBD patients. The combination of α-syn and P-tau resulted in a specificity of 99% and a sensitivity of 97% for MCI-AD. MCI-AD patients with early psychotic symptoms (n = 9) displayed a trend towards a decrease in P-tau and α-syn compared to the MCI-AD patients without psychotic symptoms (n = 23). We conclude that adding CSF α-syn to central core AD biomarkers improves an early differential diagnosis of MCI-AD from other forms of MCI. OPEN SCIENCE BADGES: This article has received a badge for *Open Materials* because it provided all relevant information to reproduce the study in the manuscript. The complete Open Science Disclosure form for this article can be found at the end of the article. More information about the Open Practices badges can be found at https://cos.io/our-services/open-science-badges/.

Levels of ADAM10 are reduced in Alzheimer's disease CSF.

BACKGROUND: The disintegrin metalloproteinase 10 (ADAM10) is the main α-secretase acting in the non-amyloidogenic processing of the amyloid precursor protein. This study assesses whether ADAM10 is present in cerebrospinal fluid (CSF), and whether it has potential as a biomarker for Alzheimer's disease (AD). METHODS: ADAM10 was characterized in human CSF samples by immunoprecipitation and western blotting using antibodies specific for different domains of the protein and by ultracentrifugation in sucrose density gradients. Samples from AD patients (n = 20) and age-matched non-AD controls (n = 20) were characterized for classical CSF biomarkers, Aß42, T-tau, or P-tau by ELISA, and assayed for soluble ADAM10 levels by western blotting. RESULTS: We found that ADAM10 is present in human CSF as several distinct species: an immature form retaining the prodomain (proADAM10; ~ 80 kDa), a mature unprocessed full-length form (ADAM10f; ~ 55 kDa), and a truncated large soluble form released from the membrane (sADAM10; ~ 50 kDa). Fractionation by ultracentrifugation on sucrose density gradients showed that the ADAM10f and sADAM10 species form large complexes. Immunoblotting revealed a significant decrease in ADAM10f and sADAM10 in AD CSF compared to control CSF, while proADAM10 levels remained unaltered. CONCLUSIONS: Several forms of ADAM10 are present in CSF, mainly assembled as high-molecular weight complexes. The determination of the levels of mature forms of CSF-ADAM10 may be useful as a biomarker for AD.

Inhibition of γ-Secretase Leads to an Increase in Presenilin-1.

γ-Secretase inhibitors (GSIs) are potential therapeutic agents for Alzheimer's disease (AD); however, trials have proven disappointing. We addressed the possibility that γ-secretase inhibition can provoke a rebound effect, elevating the levels of the catalytic γ-secretase subunit, presenilin-1 (PS1). Acute treatment of SH-SY5Y cells with the GSI LY-374973 (N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester, DAPT) augments PS1, in parallel with increases in other γ-secretase subunits nicastrin, presenilin enhancer 2, and anterior pharynx-defective 1, yet with no increase in messenger RNA expression. Over-expression of the C-terminal fragment (CTF) of APP, C99, also triggered an increase in PS1. Similar increases in PS1 were evident in primary neurons treated repeatedly (4 days) with DAPT or with the GSI BMS-708163 (avagacestat). Likewise, rats examined after 21 days administered with avagacestat (40 mg/kg/day) had more brain PS1. Sustained γ-secretase inhibition did not exert a long-term effect on PS1 activity, evident through the decrease in CTFs of APP and ApoER2. Prolonged avagacestat treatment of rats produced a subtle impairment in anxiety-like behavior. The rebound increase in PS1 in response to GSIs must be taken into consideration for future drug development.

C-terminal fragments of the amyloid precursor protein in cerebrospinal fluid as potential biomarkers for Alzheimer disease.

This study assesses whether C-terminal fragments (CTF) of the amyloid precursor protein (APP) are present in cerebrospinal fluid (CSF) and their potential as biomarkers for Alzheimer's disease (AD). Immunoprecipitation and simultaneous assay by Western blotting using multiplex fluorescence imaging with specific antibodies against particular domains served to characterize CTFs of APP in human CSF. We demonstrate that APP-CTFs are detectable in human CSF, being the most abundant a 25-kDa fragment, probably resulting from proteolytic processing by η-secretase. The level of the 25-kDa APP-CTF was evaluated in three independent CSF sample sets of patients and controls. The CSF level of this 25-kDa CTF is higher in subjects with autosomal dominant AD linked to PSEN1 mutations, in demented Down syndrome individuals and in sporadic AD subjects compared to age-matched controls. Our data suggest that APP-CTF could be a potential diagnostic biomarker for AD.

HNK-1 Carrier Glycoproteins Are Decreased in the Alzheimer's Disease Brain.

The human natural killer-1 (HNK-1), 3-sulfonated glucuronic acid, is a glycoepitope marker of cell adhesion that participates in cell-cell and cell-extracellular matrix interactions and in neurite growth. Very little is known about the regulation of the HNK-1 glycan in neurodegenerative disease, particularly in Alzheimer's disease (AD). In this study, we investigate changes in the levels of HNK-1 carrier glycoproteins in AD. We demonstrate an overall decrease in HNK-1 immunoreactivity in glycoproteins extracted from the frontal cortex of AD subjects, compared with levels from non-demented controls (NDC). Immunoblotting of ventricular post-mortem and lumbar ante-mortem cerebrospinal fluid with HNK-1 antibodies indicate similar levels of carrier glycoproteins in AD and NDC samples. Decrease in HNK-1 carrier glycoproteins were not paralleled by changes in messenger RNA (mRNA) levels of the enzymes involved in the synthesis of the glycoepitope, ß-1,4-galactosyltransferase (ß4GalT), glucuronyltransferases GlcAT-P and GlcAT-S, or sulfotransferase HNK-1ST. Over-expression of amyloid precursor protein in Tg2576 transgenic mice and in vitro treatment of SH-SY5Y neuroblastoma cells with the amyloidogenic Aß42 peptide resulted in a decrease in HNK-1 immunoreactivity levels in brain and cellular extracts, whereas the levels of soluble HNK-1 glycoproteins detected in culture media were not affected by Aß treatment. HNK-1 levels remain unaffected in the brain extracts of Tg-VLW mice, a model of mutant hyperphosphorylated tau, and in SH-SY5Y cells over-expressing hyperphosphorylated wild-type tau. These results provide evidence that cellular levels of HNK-1 carrier glycoforms are decreased in the brain of AD subjects, probably influenced by the ß-amyloid protein.

Cerebrospinal fluid Presenilin-1 increases at asymptomatic stage in genetically determined Alzheimer's disease.

BACKGROUND: Presenilin-1 (PS1), the active component of the intramembrane γ-secretase complex, can be detected as soluble heteromeric aggregates in cerebrospinal fluid (CSF). The aim of this study was to examine the different soluble PS1 complexes in the lumbar CSF (CSF-PS1) of individuals with Alzheimer's disease (AD), particularly in both symptomatic and asymptomatic genetically determined AD, in order to evaluate their potential as early biomarkers. METHODS: Western blotting, differential centrifugation and co-immunoprecipitation served to determine and characterize CSF-PS1 complexes. We also monitored the assembly of soluble PS1 into complexes in a cell model, and the participation of Aß in the dynamics and robustness of the stable PS1 complexes. RESULTS: There was an age-dependent increase in CSF-PS1 levels in cognitively normal controls, the different complexes represented in similar proportions. The total levels of CSF-PS1, and in particular the proportion of the stable 100-150 kDa complexes, increased in subjects with autosomal dominant AD that carried PSEN1 mutations (eight symptomatic and six asymptomatic ADAD) and in Down syndrome individuals (ten demented and ten non-demented DS), compared with age-matched controls (n = 23), even prior to the appearance of symptoms of dementia. The proportion of stable CSF-PS1 complexes also increased in sporadic AD (n = 13) and mild-cognitive impaired subjects (n = 12), relative to age-matched controls (n = 17). Co-immunoprecipitation demonstrated the association of Aß oligomers with soluble PS1 complexes, particularly the stable complexes. CONCLUSIONS: Our data suggest that CSF-PS1 complexes may be useful as an early biomarker for AD, reflecting the pathology at asymptomatic state.

Increased Expression of Readthrough Acetylcholinesterase Variants in the Brains of Alzheimer's Disease Patients.

Alzheimer's disease (AD) is characterized by a decrease in the enzymatic activity of the enzyme acetylcholinesterase (AChE). AChE is expressed as multiple splice variants, which may serve both cholinergic degradative functions and non-cholinergic functions unrelated with their capacity to hydrolyze acetylcholine. We have recently demonstrated that a prominent pool of enzymatically inactive AChE protein exists in the AD brain. In this study, we analyzed protein and transcript levels of individual AChE variants in human frontal cortex from AD patients by western blot analysis using specific anti-AChE antibodies and by quantitative real-time PCR (qRT-PCR). We found similar protein and mRNA levels of the major cholinergic "tailed"-variant (AChE-T) and the anchoring subunit, proline-rich membrane anchor (PRiMA-1) in frontal cortex obtained from AD patients and non-demented controls. Interestingly, we found an increase in the protein and transcript levels of the non-cholinergic "readthrough" AChE (AChE-R) variants in AD patients compared to controls. Similar increases were detected by western blot using an antibody raised against the specific N-terminal domain, exclusive of alternative N-extended variants of AChE (N-AChE). In accordance with a subset of AChE-R monomers that display amphiphilic properties that are upregulated in the AD brain, we demonstrate that the increase of N-AChE species is due, at least in part, to N-AChE-R variants. In conclusion, we demonstrate selective alterations in specific AChE variants in AD cortex, with no correlation in enzymatic activity. Therefore, differential expression of AChE variants in AD may reflect changes in the pathophysiological role of AChE, independent of cholinergic impairment or its role in degrading acetylcholine.

Neuromuscular Junction Impairment in Amyotrophic Lateral Sclerosis: Reassessing the Role of Acetylcholinesterase.

Amyotrophic Lateral Sclerosis (ALS) is a highly debilitating disease caused by progressive degeneration of motorneurons (MNs). Due to the wide variety of genes and mutations identified in ALS, a highly varied etiology could ultimately converge to produce similar clinical symptoms. A major hypothesis in ALS research is the "distal axonopathy" with pathological changes occurring at the neuromuscular junction (NMJ), at very early stages of the disease, prior to MNs degeneration and onset of clinical symptoms. The NMJ is a highly specialized cholinergic synapse, allowing signaling between muscle and nerve necessary for skeletal muscle function. This nerve-muscle contact is characterized by the clustering of the collagen-tailed form of acetylcholinesterase (ColQ-AChE), together with other components of the extracellular matrix (ECM) and specific key molecules in the NMJ formation. Interestingly, in addition to their cholinergic role AChE is thought to play several "non-classical" roles that do not require catalytic function, most prominent among these is the facilitation of neurite growth, NMJ formation and survival. In all this context, abnormalities of AChE content have been found in plasma of ALS patients, in which AChE changes may reflect the neuromuscular disruption. We review these findings and particularly the evidences of changes of AChE at neuromuscular synapse in the pre-symptomatic stages of ALS.