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- Klionsky, Daniel J., et al.
(author)
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Guidelines for the use and interpretation of assays for monitoring autophagy
- 2012
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In: Autophagy. - : Informa UK Limited. - 1554-8635 .- 1554-8627. ; 8:4, s. 445-544
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Research review (peer-reviewed)abstract
- In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.
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| 3. |
- Aoyagi, Atsushi, et al.
(author)
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A beta and tau prion-like activities decline with longevity in the Alzheimer's disease human brain
- 2019
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In: Science Translational Medicine. - : AMER ASSOC ADVANCEMENT SCIENCE. - 1946-6234 .- 1946-6242. ; 11:490
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Journal article (peer-reviewed)abstract
- The hallmarks of Alzheimer's disease (AD) are the accumulation of A beta plaques and neurofibrillary tangles composed of hyperphosphorylated tau. We developed sensitive cellular assays using human embryonic kidney-293T cells to quantify intracellular self-propagating conformers of A beta in brain samples from patients with AD or other neurodegenerative diseases. Postmortem brain tissue from patients with AD had measurable amounts of pathological A beta conformers. Individuals over 80 years of age had the lowest amounts of prion-like A beta and phosphorylated tau. Unexpectedly, the longevity-dependent decrease in self-propagating tau conformers occurred in spite of increasing amounts of total insoluble tau. When corrected for the abundance of insoluble tau, the ability of postmortem AD brain homogenates to induce misfolded tau in the cellular assays showed an exponential decrease with longevity, with a half-life of about one decade over the age range of 37 to 99 years. Thus, our findings demonstrate an inverse correlation between longevity in patients with AD and the abundance of pathological tau conformers. Our cellular assays can be applied to patient selection for clinical studies and the development of new drugs and diagnostics for AD.
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| 5. |
- Condello, Carlo, et al.
(author)
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Structural heterogeneity and intersubject variability of A beta in familial and sporadic Alzheimer's disease
- 2018
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In: Proceedings of the National Academy of Sciences of the United States of America. - : NATL ACAD SCIENCES. - 0027-8424 .- 1091-6490. ; 115:4, s. E782-E791
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Journal article (peer-reviewed)abstract
- Point mutations in the amyloid-beta (A beta) coding region produce a combination of mutant and WT A beta isoforms that yield unique clinicopathologies in familial Alzheimer's disease (fAD) and cerebral amyloid angiopathy (fCAA) patients. Here, we report a method to investigate the structural variability of amyloid deposits found in fAD, fCAA, and sporadic AD (sAD). Using this approach, we demonstrate that mutant A beta determines WT A beta conformation through prion template-directed misfolding. Using principal component analysis of multiple structure-sensitive fluorescent amyloid-binding dyes, we assessed the conformational variability of A beta deposits in fAD, fCAA, and sAD patients. Comparing many deposits from a given patient with the overall population, we found that intrapatient variability is much lower than interpatient variability for both disease types. In a given brain, we observed one or two structurally distinct forms. When two forms coexist, they segregate between the parenchyma and cerebrovasculature, particularly in fAD patients. Compared with sAD samples, deposits from fAD patients show less intersubject variability, and little overlap exists between fAD and sAD deposits. Finally, we examined whether E22G (Arctic) or E22Q (Dutch) mutants direct the misfolding of WT A beta, leading to fAD-like plaques in vivo. Intracerebrally injecting mutant A beta 40 fibrils into transgenic mice expressing only WT A beta induced the deposition of plaques with many biochemical hallmarks of fAD. Thus, mutant A beta 40 prions induce a conformation of WT A beta similar to that found in fAD deposits. These findings indicate that diverse AD phenotypes likely arise from one or more initial A beta prion conformations, which kinetically dominate the spread of prions in the brain.
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| 6. |
- Condello, Carlo, et al.
(author)
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A beta and tau prions feature in the neuropathogenesis of Down syndrome
- 2022
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In: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 119:46
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Journal article (peer-reviewed)abstract
- Down syndrome (DS) is caused by the triplication of chromosome 21 and is the most common chromosomal disorder in humans. Those individuals with DS who live beyond age 40 y develop a progressive dementia that is similar to Alzheimer's disease (AD). Both DS and AD brains exhibit numerous extracellular amyloid plaques composed of A beta and intracellular neurofibrillary tangles composed of tau. Since AD is a double-prion disorder, we asked if both A beta and tau prions feature in DS. Frozen brains from people with DS, familial AD (fAD), sporadic AD (sAD), and age-matched controls were procured from brain biorepositories. We selectively precipitated A beta and tau prions from DS brain homogenates and measured the number of prions using cellular bioassays. In brain extracts from 28 deceased donors with DS, ranging in age from 19 to 65 y, we found nearly all DS brains had readily measurable levels of A beta and tau prions. In a cross-sectional analysis of DS donor age at death, we found that the levels of A beta and tau prions increased with age. In contrast to DS brains, the levels of A beta and tau prions in the brains of 37 fAD and sAD donors decreased as a function of age at death. Whether DS is an ideal model for assessing the efficacy of putative AD therapeutics remains to be determined.
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| 7. |
- Condello, C, et al.
(author)
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Structural heterogeneity and intersubject variability of Aβ in familial and sporadic Alzheimer's disease
- 2018
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In: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 1091-6490. ; 115:4, s. E782-E791
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Journal article (peer-reviewed)abstract
- An expanding body of evidence argues that the Aβ and tau proteins share important characteristics of prion propagation to cause pathogenesis in Alzheimer’s disease (AD). Aβ and tau form a number of amyloids (β-sheet–rich structures) with distinct conformations (“strains”), some of which give rise to different diseases and associated pathologies. We develop new probes of amyloid structure and use these to identify conformational strains of Aβ in heritable and sporadic forms of AD patient samples. We demonstrate that distinct strains of Aβ can be discerned in different disease types, or in different brain compartments within a given patient. Our findings may potentially explain the spectrum of clinical and pathologic features observed in AD.
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