Biology subjects

Braun, A. R.

Publications and source records attributed to Braun, A. R..

5 recordsLinked to original sources

bioRxiv2026

From anti-fungal to potential neurotherapeutic: Posaconazole as an effective inhibitor of cellular TDP-43 pathology

Recently, we showed that ketoconazole, a known anti-fungal inhibitor of CYP51, stabilized TAR DNA-binding protein 43 (TDP-43) native self-interactions, reduced TDP-43 pathology and rescued TDP-43-induced SREBP2 downregulation. Despite its promising effects, ketoconazole is not viable for repurposing for ALS due to liver toxicity side effects that occur when orally delivered. To address this, we tested the activities of seven additional known azole-based CYP51 inhibitors in order identify a viable alternative to ketoconazole. Using our established TDP-43 mislocalization and aggregation assay in HEK293T cells, we identified posaconazole, an FDA-approved, CNS-penetrant and orally delivered anti-fungal, as the strongest inhibitor of TDP-43 pathology. Posaconazole was able to reduce insoluble TDP-43 and restore SREBP2 levels, outperforming ketoconazole. Mechanism of action (MOA) experiments suggest posaconazole is able to outperform ketoconazole by inducing a significantly stronger activation of autophagy and upregulation of heat shock proteins known to clear TDP-43. Further MOA experiments show that the effects of posaconazole on TDP-43 are dependent on its known ability to lower cellular cholesterol levels. By correlating our experimental results on the eight CYP51 inhibitors tested, we show that predicted affinity towards human CYP51 strongly correlates with the inhibitors ability to lower TDP-43 aggregation and mislocalization. Finally, we tested posaconazole in a low dose sodium arsenite ALS model in iPSC-derived motor neurons, showing that it is efficacious at inhibiting TDP-43 pathology in the nanomolar range. Altogether, these results support the repurposing of posaconazole for ALS/FTD as a means to prevent TDP-43 pathology.

cell biology↗

bioRxiv2024

Fluorescence lifetime-based FRET biosensors for monitoring N-terminal domain interactions of TDP-43 in living cells: A novel resource for ALS and FTD drug discovery

TAR DNA-binding protein 43 (TDP-43) pathological aggregates are widely implicated in Alzheimers disease, frontotemporal dementia and amyotrophic lateral sclerosis. While therapeutic platforms targeting TDP-43 have predominantly targeted its aggregation, recent findings suggest that loss of functional TDP-43 dimers and multimers -- essential for RNA processing -- occur upstream of aggregation and is driven through disruption of N-terminal domain (NTD) interactions. Here, we demonstrate that these interactions are targetable via cellular fluorescence lifetime-based FRET biosensors which we used to screen the FDA-approved Selleck library. Our NTD-specific hit ketoconazole rescues sorbitol-induced TDP-43 mislocalization and aggregation, and ameliorates TDP-43 induced downregulation of SREBP2, a TDP-43 mRNA binding target with known implication in ALS. In addition, ketoconazole improves neurite outgrowth in a TDP-43 overexpressing neuron model and motor dysfunction in TDP-43 overexpressing C. elegans. Taken together, our platform represents a novel approach for targeting NTD-dependent TDP-43 interactions, and the identification of ketoconazole validates an exciting translational premise for TDP-43 drug discovery.

neuroscience↗

bioRxiv2020

Potent inhibitors of toxic alpha-synuclein oligomers identified via cellular time-resolved FRET biosensor.

Preventing or reversing the pathological misfolding and self-association of alpha-synuclein (aSyn) can rescue a broad spectrum of pathological cellular insults that manifest in Parkinsons Disease (PD), Dementia with Lewy bodies (DLB), and other alpha-synucleinopathies. We have developed a high-throughput, FRET-based drug discovery platform that combines high-resolution protein structural detection in living cells with an array of functional and biophysical assays to identify novel lead compounds that protect SH-SY5Y cells from aSyn induced cytotoxicity as well as inhibiting seeded aSyn aggregation, even at nanomolar concentrations. Our combination of cellular and cell-free assays allow us to distinguish between direct aSyn binding or indirect mechanisms of action (MOA). We focus on targeting oligomers with the requisite sensitivity to detect subtle protein structural changes that may lead to effective therapeutic discoveries for PD, DLB, and other alpha-synucleinopathies. Pilot high-throughput screens (HTS) using our aSyn cellular FRET biosensors has led to the discovery of the first nanomolar-affinity small molecules that disrupt toxic aSyn oligomers in cells and inhibit cell death. Primary neuron assays of aSyn pathology (e.g. phosphorylation of mouse aSyn PFF) show rescue of pathology for two of our tested compounds. Subsequent seeded thioflavin-t (ThioT) aSyn aggregation assays demonstrate these compounds deter or block aSyn fibril assembly. Other hit compounds identified in our HTS are known to modulate oxidative stress, autophagy, and ER stress, providing validation that our biosensor is sensitive to indirect MOA as well.

neuroscience↗

bioRxiv2019

A novel small molecule screening platform for disrupting toxic tau oligomers in cells

Tauopathies, including Alzheimers disease, are a group of neurodegenerative disorders characterized by pathological aggregation of the microtubule binding protein tau. Recent studies suggest that toxic tau oligomers, which are soluble and distinct from insoluble beta-sheet fibrils, are central players in neuronal cell death. To exploit this new therapeutic window, we engineered two first-in-class FRET based biosensors that monitor tau conformations in cells. Because this new technology platform operates in cells, it enables high-throughput screening of small molecules that target tau oligomers while avoiding the uncertainties of idiosyncratic in vitro preparations of tau assemblies from purified protein. We found a small molecule, MK-886, that disrupts tau oligomers and reduces tau-induced cell cytotoxicity with nanomolar potency. Using SPR and an advanced single-molecule FRET technique, we show that MK-886 directly binds to tau and specifically perturbs the folding of tau monomer in the proline-rich and microtubule-binding regions. Furthermore, we show that MK-886 accelerates the tau aggregation lag phase using a thioflavin-T assay, implying that the compound stabilizes a non-toxic, on-pathway oligomer. The technology described here should generalize to the study and targeting of conformational ensembles within the aggregation pathways of most intrinsically disordered proteins.

neuroscience↗

bioRxiv2018

Overt social interaction and resting state in autism: core and contextual neural features

Conversation is an important and ubiquitous social behavior. Individuals with Autism Spectrum Disorder (autism) without intellectual disability often have normal structural language abilities but deficits in social aspects of communication like pragmatics, prosody, and eye contact. Previous studies of resting state activity suggest that intrinsic connections among neural circuits involved with social processing are disrupted in autism, but to date no neuroimaging study has examined neural activity during the most commonplace yet challenging social task: spontaneous conversation. Here we used functional MRI to scan autistic males (N=19) without intellectual disability and age- and IQ-matched typically developing controls (N=20) while they engaged in a total of 193 face-to-face interactions. Participants completed two kinds of tasks: Conversation, which had high social demand, and Repetition, which had low social demand. Autistic individuals showed abnormally increased task-driven inter-regional temporal correlation relative to controls, especially among social processing regions and during high social demand. Furthermore, these increased correlations were associated with parent ratings of participants social impairments. These results were then compared with previously-acquired resting-state data (56 Autism, 62 Control participants). While some inter-regional correlation levels varied by task or rest context, others were strikingly similar across both task and rest, namely increased correlation among the thalamus, dorsal and ventral striatum, somatomotor, temporal and prefrontal cortex in the autistic individuals, relative to the control groups. These results suggest a basic distinction. Autistic cortico-cortical interactions vary by context, tending to increase relative to controls during Task and decrease during Rest. In contrast, striato- and thalamocortical relationships with socially engaged brain regions are increased in both Task and Rest, and may be core to the condition of autism.

neuroscience↗