Increased expression of fragmented tRNA promoted neuronal necrosis

Abstract

Neuronal necrosis induced by excessive glutamate release is well known to contribute morbidity and mortality in ischemic stroke. Over the past decades, strategies on targeting glutamate receptor did not achieve desirable clinical outcomes. Finding the downstream mechanism of the glutamate receptor activation may provide new targets to suppress the cell death. Previously, our study demonstrated that the increase of H3K4 trimethylation (H3K4me3) played a key detrimental role on neuronal necrosis; however, the mechanism of this histone modification is unclear. Through a genome-wide small RNA sequencing, we identified several tRNA-derived fragments (tRFs) and piwi-interacting RNA (piRNAs) species were enriched in glutamate-induced neuronal necrosis in rat primary neuron cultures, and this enrichment was dependent on the H3K4me3 increase. Strikingly, when we transfected several synthesized tRFs and piRNA species into neurons, the tRFs but not the piRNAs induced neuron swelling and death. The cell death morphology recapitulated neuronal necrosis induced by glutamate. For the cytotoxic effect of tRFs, our data suggested that protein synthesis was inhibited likely through induction of ribosomal stalling. By proteomic analysis of tRFs effect, the most affected pathway was enriched in the mitochondrial metabolism. Consistently, mitochondrial fragmentation was increased in neuronal necrosis, and suppression of mitochondrial fission by genetic manipulation or drug rescued neuronal necrosis. Using our previously established Drosophila model of neuronal necrosis, we found that inhibition of small RNA transcription, blocking RNA transport from nucleus to cytosol, or knocking down Ago1/2 to suppress the RNA interference effect, all rescued the fly death, suggesting transcription and processing of small RNAs contribute to neuronal necrosis. Together, these results indicate that the abnormal transcription of tRFs may play a key role downstream of the H3K4me3 increase. This provides a potential new strategy to suppress neuronal necrosis.

tRNA Modifications and Dysregulation: Implications for Brain Diseases

“…This mechanism may result in neuronal demise, marked by elevated glutamate release, mitochondrial dysfunction, and eventual onset of stroke. The identification of these tRFs highlights the possibility of modulating their expression as a means to mitigate the risk of stroke, offering a fresh perspective on stroke management and prevention [249].…”

The role of tRNA-derived small RNAs in aging

“…Angiogenin, which cleaves tRNAs into tiRNAs, promotes the survival of neuron-like SH-SY5Y cells ( 38 ), suggesting the protective roles of tiRNAs against neuronal loss. In contrast, another study using D. melanogaster and cultured rat neurons indicates that tsRNAs can cause cell swelling and necrosis by reducing translation through participation in ribosomal stalling ( 39 ). In the brains of the progeric SAMP8 mice, many tsRNAs are differentially expressed, compared with those in control mice, and their potential targets are implicated in neurodegenerative disorders ( 30 ).…”

NOCICEPTRA2.0 - a comprehensive ncRNA atlas of human native and iPSC-derived sensory neurons

“…Transfer RNAs (tRNAs) represent a well-known ncRNA species serving RNA translation into protein, however, novel regulatory functions for tRNA fragments (tRFs) have recently been reported (Anderson & Ivanov 2014;Magee & Rigoutsos 2020). tRFs are short, 16-35 nucleotides in length, and play vital roles in neuron survival, necrosis, and neurodegenerative disorders such as Parkinson and Alzheimer's disease, but have not been explored in neuronal development (Cao et al 2021;Inoue et al 2020;Mathew et al 2022;Schaffer et al 2019;Wu et al 2021). tRNAs and tRFs exhibited pronounced time dependent expression patterns throughout iDN differentiation supporting the idea that tRNA regulatory pathways contribute to neurodevelopmental processes (Figure 1A).…”

“…In addition, fragmented mature ncRNAs such as tRNAs and snoRNAs can be incorporated into the Argonaute complex thereby mimicking the function of miRNAs (Guan et al 2020;Kumar et al 2014). For example, upregulation of tRNA fragments inducing neuronal necrosis is detectable in post stroke patient blood samples (Cao et al 2021;Winek et al 2020).…”