Biology subjects

Kharel, P.

Publications and source records attributed to Kharel, P..

3 recordsLinked to original sources

bioRxiv2022

Stress promotes RNA G-quadruplex folding in human cells

Guanine-rich nucleic acids can fold into G-quadruplex (G4) structures. Although endogenous RNAs contain sequences that can fold into RNA G4s (rG4s) in vitro, their folding and functions in vivo are not well understood. We show that the folding of putative rG4s in human cells into bona fide rG4 structures is dynamically regulated by stress. By using a high-throughput approach based on differential reactivity of dimethyl sulfate (DMS) towards Gs within folded vs unfolded rG4s, we identified hundreds of endogenous rG4s whose folding is promoted by cellular stress and validated them using a newly developed rG4-specific ligand. Stress-dependent rG4s are enriched in mRNA 3'-untranslated regions, suggesting their role in regulating mRNA stability under stress. Lastly, rG4 folding is reversible upon stress removal or adaptation. Our study show that rG4s function as regulatory elements in regulating mRNA stability and cellular stress response. One-Sentence SummaryRNA G-quadruplexes assemble under stress in human cells

molecular biology↗

bioRxiv2021

Lysosomal Exocytosis Releases Pathogenic α-Synuclein Species from Neurons

Considerable evidence supports the release of pathogenic aggregates of the neuronal protein -Synuclein (Syn) into the extracellular space. While this release is proposed to instigate the neuron-to-neuron transmission and spread of Syn pathology in synucleinopathies including Parkinsons disease, the molecular-cellular mechanism(s) remain unclear. Here we show that pathogenic species of Syn accumulate within neuronal lysosomes in mouse brains and primary neurons. We then find that neurons release these pathogenic Syn species via SNARE-dependent lysosomal exocytosis; proposing a central mechanism for exocytosis of aggregated and degradation-resistant proteins from neurons.

cell biology↗

bioRxiv2020

NAT8L mRNA oxidation is linked to neurodegeneration in multiple sclerosis

RNA oxidation has been implicated in neurodegeneration, but the underlying mechanism for such effects is unclear. Recently, we demonstrated extensive RNA oxidation within the neurons in multiple sclerosis (MS) brain. In this report we identified selectively oxidized mRNAs in neuronal cells that pertained to neuropathological pathways. N-acetyl aspartate transferase 8 like (NAT8L) mRNA is one such transcript, whose translated product enzymatically synthesizes N-acetyl aspartic acid (NAA), a neuronal metabolite important for myelin synthesis. We reasoned that impediment of translation of an oxidized NAT8L mRNA will result in reduction in its cognate protein, thus lowering NAA level. This assertion is directly supported by our studies on a model cellular system, an MS animal model and postmortem human MS brain. Reduced NAA level in the brain hampers myelin integrity making neuronal axons more susceptible to damage, which contributes in MS neurodegeneration. Overall, this work provides a framework for mechanistic understanding of the link between RNA oxidation and neurodegenerative diseases.

molecular biology↗