Biology subjects

Bitan, G.

Publications and source records attributed to Bitan, G..

3 recordsLinked to original sources

bioRxiv2025

Development of an RNA Aptamer as a Therapeutic Agent for Synucleinopathies

The aggregation of -synuclein (Syn), a 140-mer protein, has been implicated in the pathogenesis of Parkinsons disease, multiple system atrophy, and dementia with Lewy bodies. KTKEGV repeats (KR) of Syn are key mediators of prion-like propagation and neurodegeneration. Despite the availability of symptomatic treatments, no current therapy effectively delays disease progression. Here we report a 77-nucleotide (nt) RNA aptamer (1R6) with potent affinity and selectivity for Syn1-95 (KD = 18 nM) through in vitro selection. 1R6 significantly inhibited Syn oligomerization and {beta}-sheet-rich fibril assembly and promoted disaggregation of preformed fibrils. Additionally, 1R6 suppressed Syn seeding, as determined by FRET-based cellular biosensor cell assay. Cellular studies revealed that 1R6 cotransfection completely prevented Syn-induced cytotoxicity. To assess the protective effects of 1R6 in vivo, we used a Drosophila melanogaster model expressing human Syn in neurons. Flies fed with 1R6 showed improved locomotor defects, reduced photoreceptor degeneration, and decreased Syn levels in the head. Structural characterization through 1H-15N heteronuclear multiple quantum correlation nuclear magnetic resonance experiments demonstrated that 1R6 targets KR motifs, a finding further supported by in silico simulations. Our findings indicate that RNA aptamers, such as 1R6, may represent promising therapeutic candidates for synucleinopathies, thus opening new avenues in the treatment of these diseases.

neuroscience↗

bioRxiv2025

Allosteric Modulation of Pathological Ataxin-3 Aggregation: A Path to Spinocerebellar Ataxia Type-3 Therapies

Spinocerebellar ataxia type 3 (SCA3) is a rare inherited neurodegenerative disease caused by the expansion of a polyglutamine repeat in the protease ataxin-3 (Atx3). Despite extensive knowledge of the downstream pathophysiology, no disease-modifying therapies are currently available to halt disease progression. The accumulation of protein inclusions enriched in the polyQ-expanded Atx3 in neurons suggests that inhibiting its self-assembly may yield targeted therapeutic approaches. Here it is shown that a supramolecular tweezer, CLR01, binds to a lysine residue on a positively charged surface patch of the Atx3 catalytic Josephin domain. At this site, the binding of CLR01 decreases the conformational fluctuations of the distal flexible hairpin. This results in reduced exposure of the nearby aggregation-prone region, which overlaps with the substrate ubiquitin binding site and primes Atx3 self-assembly, ultimately delaying Atx3 amyloid fibril formation and reducing the secondary nucleation rate, a process linked to fibril proliferation and toxicity. These effects translate into the reversal of synapse loss in a SCA3 cultured cortical neuron model, an improved locomotor function in a C. elegans SCA3 model, and a delay in disease onset, accompanied by reduced severity of motor symptoms in a SCA3 mouse model. This study provides critical insights into Atx3 self-assembly, revealing a novel allosteric site for designing CLR01-inspired therapies targeting pathological aggregation pathways while sparing essential functional sites. These findings emphasize that targeting allosteric sites in amyloid-forming proteins may offer unique opportunities to develop safe therapeutic strategies for various protein misfolding disorders.

biophysics↗

bioRxiv2021

Exophers are components of mammalian cell neurobiology in health and disease

Maintenance of cellular homeostasis is critically important for the survival of cells and organisms. Degradation and recycling of biomolecules and whole organelles is an essential mechanism for maintaining cellular homeostasis. The main systems responsible for these processes are the ubiquitin-proteasome system and autophagy-lysosome pathway. Another mechanism was reported in c. elegans--formation of large, membrane-enclosed projections called "exophers," into which cells direct debris and toxic protein aggregates1. Exophers were shown to act as large, temporary disposal compartments that disconnected from the cells within several hours. Here, we report the discovery of exophers in the mammalian brain, including the brains of humans and mice. Similar to those described in nematodes, the mammalian exophers appear to emanate from the cell body, initially connected by a nanotube, and eventually disconnect. Rare, innate exophers were found in healthy human brain and primary neurons from wild-type mice, presumably mediating transfer of large cargo between cells. The number of exophers increased as an adaptive response under proteostatic stress, e.g., in Alzheimers disease brain or in primary neurons from two tauopathy mouse models, where the exophers likely facilitated expulsion of proteotoxic material. Our findings suggest that exopherogenesis is a rare, innate house-keeping process that is elevated adaptively in response to proteostatic pressure and is a conserved mechanism from nematodes to humans.

cell biology↗