Developmental regulation of mitochondrial apoptosis by c-Myc governs age- and tissue-specific sensitivity to cancer therapeutics

It is not understood why healthy tissues can exhibit varying levels of sensitivity to the same toxic stimuli. Using BH3 profiling, we find that mitochondria of many adult somatic tissues, including brain, heart, and kidneys, are profoundly refractory to pro-apoptotic signaling, leading to cellular resistance to cytotoxic chemotherapies and ionizing radiation. In contrast, mitochondria from these tissues in young mice and humans are primed for apoptosis, predisposing them to undergo cell death in response to genotoxic damage. While expression of the apoptotic protein machinery is nearly absent by adulthood, in young tissues its expression is driven by c-Myc, linking developmental growth to cell death. These differences may explain why pediatric cancer patients have a higher risk of developing treatment-associated toxicities

Brain region-specific susceptibility of Lewy body pathology in synucleinopathies is governed by α-synuclein conformations

The protein α-synuclein, a key player in Parkinson's disease (PD) and other synucleinopathies, exists in different physiological conformations: cytosolic unfolded aggregation-prone monomers and helical aggregation-resistant multimers. It has been shown that familial PD-associated missense mutations within the α-synuclein gene destabilize the conformer equilibrium of physiologic α-synuclein in favor of unfolded monomers. Here, we characterized the relative levels of unfolded and helical forms of cytosolic α-synuclein in post-mortem human brain tissue and showed that the equilibrium of α-synuclein conformations is destabilized in sporadic PD and DLB patients. This disturbed equilibrium is decreased in a brain region-specific manner in patient samples pointing toward a possible "prion-like" propagation of the underlying pathology and forms distinct disease-specific patterns in the two different synucleinopathies. We are also able to show that a destabilization of multimers mechanistically leads to increased levels of insoluble, pathological α-synuclein, while pharmacological stabilization of multimers leads to a "prion-like" aggregation resistance. Together, our findings suggest that these disease-specific patterns of α-synuclein multimer destabilization in sporadic PD and DLB are caused by both regional neuronal vulnerability and "prion-like" aggregation transmission enabled by the destabilization of local endogenous α-synuclein protein

Lessons from a Rare Familial Dementia: Amyloid and Beyond

Here we review the similarities between a rare inherited disorder, familial British dementia (FBD), and the most common of all late-life neurological conditions, Alzheimer's diseases (AD). We describe the symptoms, pathology and genetics of FBD, the biology of the BRI2 protein and mouse models of FBD and familial Danish dementia. In particular, we focus on the evolving recognition of the importance of protein oligomers and aberrant processing of the amyloid β-protein precursor (APP) - themes that are common to both FBD and AD. The initial discovery that FBD is phenotypically similar to AD, but associated with the deposition of an amyloid peptide (ABri) distinct from the amyloid β-protein (Aβ) led many to assume that amyloid production alone is sufficient to initiate disease and that ABri is the molecular equivalent of Aβ. Parallel with work on Aβ, studies of ABri producing animal models and in vitro ABri toxicity experiments caused a revision of the amyloid hypothesis and a focus on soluble oligomers of Aβ and ABri. Contemporaneous other studies suggested that loss of the ABri precursor protein (BRI2) may underlie the cognitive deficits in FBD. In this regard it is important to note that BRI2 has been shown to interact with and regulate the processing of APP, and that mutant BRI2 leads to altered cleavage of APP. A synthesis of these results suggests that a “two-hit mechanism” better explains FBD than earlier toxic gain of function and toxic loss of function models. The lessons learned from the study of FBD imply that the molecular pathology of AD is also likely to involve both aberrant aggregation (in AD, Aβ) and altered APP processing. With regard to FBD, we propose that the C-terminal 11 amino acid of FBD-BRI2 interfere with both the normal function of BRI2 and promotes the production of cystine cross-linked toxic ABri oligomers. In this scenario, loss of BRI2 function leads to altered APP processing in as yet underappreciated ways. Given the similarities between FBD and AD it seems likely that study of the structure of ABri oligomers and FBD-induced changes in APP metabolites will further our understanding of AD

Real-Time Monitoring of Alzheimer's-Related Amyloid Aggregation via Probe Enhancement-Fluorescence Correlation Spectroscopy.

This work describes the use of fluorescence correlation spectroscopy (FCS) and a novel amyloid-binding fluorescent probe, ARCAM 1, to monitor the aggregation of the Alzheimer's disease-associated amyloid β-peptide (Aβ). ARCAM 1 exhibits a large increase in fluorescence emission upon binding to Aβ assemblies, making it an excellent candidate for probe enhancement FCS (PE-FCS). ARCAM 1 binding does not change Aβ aggregation kinetics. It also exhibits greater dynamic range as a probe in reporting aggregate size by FCS in Aβ, when compared to thioflavin T (ThT) or an Aβ peptide modified with a fluorophore. Using fluorescent burst analysis (via PE-FCS) to follow aggregation of Aβ, we detected soluble aggregates at significantly earlier time points compared to typical bulk fluorescence measurements. Autocorrelation analysis revealed the size of these early Aβ assemblies. These results indicate that PE-FCS/ARCAM 1 based assays can detect and provide size characterization of small Aβ aggregation intermediates during the assembly process, which could enable monitoring and study of such aggregates that transiently accumulate in biofluids of patients with Alzheimer's and other neurodegenerative diseases

Real-Time Monitoring of Alzheimer’s-Related Amyloid Aggregation via Probe Enhancement–Fluorescence Correlation Spectroscopy

This work describes the use of fluorescence correlation spectroscopy (FCS) and a novel amyloid-binding fluorescent probe, ARCAM <b>1</b>, to monitor the aggregation of the Alzheimer’s disease-associated amyloid β-peptide (Aβ). ARCAM <b>1</b> exhibits a large increase in fluorescence emission upon binding to Aβ assemblies, making it an excellent candidate for probe enhancement FCS (PE-FCS). ARCAM <b>1</b> binding does not change Aβ aggregation kinetics. It also exhibits greater dynamic range as a probe in reporting aggregate size by FCS in Aβ, when compared to thioflavin T (ThT) or an Aβ peptide modified with a fluorophore. Using fluorescent burst analysis (via PE-FCS) to follow aggregation of Aβ, we detected soluble aggregates at significantly earlier time points compared to typical bulk fluorescence measurements. Autocorrelation analysis revealed the size of these early Aβ assemblies. These results indicate that PE-FCS/ARCAM <b>1</b> based assays can detect and provide size characterization of small Aβ aggregation intermediates during the assembly process, which could enable monitoring and study of such aggregates that transiently accumulate in biofluids of patients with Alzheimer’s and other neurodegenerative diseases