Biology subjects

Legleiter, J.

Publications and source records attributed to Legleiter, J..

3 recordsLinked to original sources

bioRxiv2025

STIP1/HOP Promotes the Formation of Cytotoxic α-Synuclein Oligomers

The accumulation of alpha-synuclein (a-Syn) as toxic oligomers, and subsequently in Lewy bodies, is a pathological hallmark of Parkinsons disease (PD) and other synucleinopathies. Molecular chaperones and co-chaperones are expected to act in concert to maintain physiological activities of proteins, including a-Syn, but in neurodegeneration this process can become mal-adaptive. Transcript levels of Stress inducible phosphoprotein 1 (STIP1), a co-chaperone of Hsp90/Hsp70, are elevated in brain samples from PD patients. In synucleinopathy mouse models, STIP1 has unexpected bidirectional effects on a-Syn, with overexpression of STIP1 aggravating a-Syn toxicity, whereas knockdown of STIP1 improves toxicity and behavioural phenotypes. However, it is unclear how STIP1 enhances the toxicity of a-Syn. Here we unravel the mechanisms by which the direct interaction between STIP1/HOP and a-Syn regulates the neurotoxicity of a-Syn. Specifically, two binding motifs in the C-terminus of a-Syn directly interact with the TPR2A domain of STIP1/HOP in a dynamic manner, competing for a shared interface on TPR2A. Binding of STIP1/HOP to a-Syn attenuates the formation of a-Syn fibrils while promoting the accumulation of high molecular weight amorphous a-Syn species. Samples of a-Syn aggregated in the presence of STIP1/HOP contain significantly more A11-positive oligomeric species and cause a greater reduction in cell viability than a-Syn aggregated in the absence of STIP1/HOP in neuronal cells. Our results provide a mechanism by which the direct interaction between STIP1/HOP and the C-terminus of a-Syn promotes the formation of cytotoxic, non-amyloidogenic, high molecular weight a-Syn species. Our model offers an explanation for the unexpected pathological link between STIP1 and a-Syn toxicity, thus opening new therapeutic avenues for the treatment of synucleinopathies.

biochemistry↗

bioRxiv2024

Blocking the ability of huntingtin to bind membranes: a therapeutic strategy for Huntingtons disease

The ordered aggregation of proteins into amyloid fibrils is a hallmark of numerous neurodegenerative diseases. A common strategy in developing therapeutics for amyloid-based diseases relies on preventing or manipulating the aggregation process. However, many amyloid-forming proteins and their aggregates bind and damage organelle and cellular membranes. As such, blocking the ability of these proteins from directly interacting with membranes represents a unique therapeutic strategy. Using a mutant huntingtin (htt) protein associated with Huntingtons disease (HD) as a model system, the viability of this strategy was evaluated. Screening over 1200 compounds for their ability to block htt binding to lipid vesicles, two compounds, Ro90-7501 (Ro) and Benzamil (Ben), were identified and validated. Despite directly interacting with htt, neither compound prevented fibril formation. Molecular dynamics simulations suggested each compound has a unique mechanism of action, consistent with experimental data. Importantly, both compounds ameliorated phenotype in a C. elegans model of HD.

biophysics↗

bioRxiv2023

Oligomerization enhances huntingtin membrane activity but is suppressed by covalent crosslinking

Huntingtin disease (HD) is a neurodegenerative disease caused by expansion of a polyglutamine (polyQ) tract within the huntingtin (htt) protein, leading to aggregation into a variety of species ranging from small oligomers to large fibrils. A consensus concerning which of these aggregate states are primarily responsible for toxicity associated with mutant htt remains elusive. Htt directly binds and damages a variety of membranous surfaces within cells. Here, the ability of different aggregation states of htt to interact with and damage lipid membranes was determined. Oligomers represented the most active lipid binding species, whereas, fibril formation severely limited membrane binding. Thus, strategies to stabilize oligomers were implemented, and conformational flexibility appeared to play a key role in the oligomer/membrane interaction. In particular, stabilizing oligomers with covalent crosslinking with 1,5-difluoro-2,4-dinitrobenzene (DFDNB) effectively eliminated the ability of oligomers to bind lipid membranes and reduced their associated cellular toxicity.

biophysics↗