Comparative interactome mapping of Tau-protein in classical and rapidly progressive Alzheimer's disease identifies subtype-specific pathways

AIMS

Tau is a key player in Alzheimer's disease (AD) and other Tauopathies. Tau pathology in the brain directly correlates with neurodegeneration in AD. The recent identification of a rapid variant of AD demands an urgent need to uncover underlying mechanisms leading to differential progression in AD. Accordingly, we aimed to dissect the underlying differential mechanisms of toxicity associated with the Tau protein in AD subtypes and to find out subtype-dependent biomarkers and therapeutic targets.

METHODS

To identify and characterise subtype-specific Tau-associated mechanisms of pathology, we performed comparative interactome mapping of Tau protein in classical AD (cAD) and rapidly progressive AD (rpAD) cases using co-immunoprecipitation coupled with quantitative mass spectrometry. The mass spectrometry data were extensively analysed using several bioinformatics approaches.

RESULTS

The comparative interactome mapping of Tau protein revealed distinct and unique interactors (DPYSL4, ARHGEF2, TUBA4A and UQCRC2) in subtypes of AD. Interestingly, an analysis of the Tau-interacting proteins indicated enrichment of mitochondrial organisation processes, including negative regulation of mitochondrion organisation, mitochondrial outer membrane permeabilisation involved in programmed cell death, regulation of autophagy of mitochondrion and necroptotic processes, specifically in the rpAD interactome. While, in cAD, the top enriched processes were related to oxidation-reduction process, transport and monocarboxylic acid metabolism.

CONCLUSIONS

Overall, our results provide a comprehensive map of Tau-interacting protein networks in a subtype-dependent manner and shed light on differential functions/pathways in AD subtypes. This comprehensive map of the Tau-interactome has provided subsets of disease-related proteins that can serve as novel biomarkers/biomarker panels and new drug targets.

Distinct microglia profile in Creutzfeldt-Jakob disease and Alzheimer's disease is independent of disease kinetics

Activated microglia represent a common pathological feature of neurodegenerative diseases. Sporadic Creutzfeldt-Jakob disease (sCJD) patients show more pronounced microglial activation than Alzheimer's disease (AD) patients. Whether these differences are due to differences in disease kinetics or represent disease-specific changes is unknown. We investigated microglial phenotypes in brains of rapidly progressive AD (rpAD) and sCJD patients matched for clinical presentation, including disease duration. We immunostained the frontal cortex, basal ganglia and cerebellum in 16 patients with rpAD and sCJD using antibodies against markers of microglia and recruited monocytes (ionized calcium-binding adaptor molecule 1, human leukocyte antigen DPQR, Cluster of Differentiation 68), an antibody unique to brain-resident microglia (transmembrane protein 119 (TMEM119)), in addition to antibodies against a marker of astrocytes (glial fibrillary acidic protein), amyloid-β (Aβ) and pathological prion protein. rpAD patients showed a distinct microglial phenotype with a high abundance of TMEM119-positive microglia in all investigated regions. Presence of Aβ deposits seen in a sCJD patient with concomitant deposition of Aβ led to increase of TMEM119-positive microglia. Our data suggest that in rpAD, activation of brain-resident microglia significantly contributes to microgliosis, whereas in sCJD the TMEM119 signature of resident microglial cells is barely detectable. This is irrespective of disease duration and may indicate disease-specific microglial reaction.

Patient with rapidly evolving neurological disease with neuropathological lesions of Creutzfeldt-Jakob disease, Lewy body dementia, chronic subcortical vascular encephalopathy and meningothelial meningioma

We report a case of rapidly evolving neurological disease in a patient with neuropathological lesions of Creutzfeldt-Jakob disease (CJD), Lewy body dementia (LBD), chronic subcortical vascular encephalopathy and meningothelial meningioma. The coexistence of severe multiple pathologies in a single patient strengthens the need to perform accurate clinical differential diagnoses in rapidly progressive dementias.

Neuropsychological predictors of rapidly progressive Alzheimer's disease

OBJECTIVE

Alzheimer's disease (AD), the most common cause of dementia, typically shows a slow clinical progression over time. 'Rapidly progressive' AD, a variant of the disease characterized by an aggressive course, exhibits distinct clinical, biological, and neuropathological features. Here, we investigate neuropsychological predictors of rapid decline in a group of mild patients with AD.

METHODS

One hundred fifty-three mild patients with AD admitted to a memory disorder clinic and followed for up to 3 years were included in this study. A comprehensive neuropsychological (NP) battery was performed at the time of enrollment. Patients were defined as 'rapidly progressive' if they exhibited a drop of 6 or more points on the Mini Mental State Examination (MMSE) between two consecutive annual visits. This event defined the main outcome in multiple analyses of variance and Cox proportional hazards models that investigated the impact of NP predictors. Categorical principal component analysis (CATPCA) was also employed in order to delineate clusters of NP tests and to test their effect on the outcome.

RESULTS

Of 153 subjects, thirty-seven (24%) were classified as 'rapidly progressive'; those subjects showed younger age of symptoms onset compared to slow decliners (68 vs 71.5 years old). Baseline lower performance on a neuropsychological test of naming predicted a rapid decline over the follow-up (P = 0.001). Three clusters of NP were defined by CATPCA: (i) executive/language, (ii) visuospatial memory, and (iii) verbal memory. The executive/language component predicted a rapid decline over the follow-up (P = 0.016).

CONCLUSION

Early executive/language impairment is highly predictive of a rapid progression of AD.