5′ValCAC tRNA fragment generated as part of a protective angiogenin response provides prognostic value in amyotrophic lateral sclerosis

Abstract

Loss-of-function mutations in the ribonuclease angiogenin are associated with amyotrophic lateral sclerosis. Angiogenin has been shown to cleave transfer RNAs during stress to produce ‘transfer-derived stress-induced RNAs’ (‘tiRNAs’). Stress-induced tRNA cleavage is preserved from single-celled organisms to humans indicating it represents part of a highly conserved stress response. However, to date the role of tRNA cleavage in amyotrophic lateral sclerosis remains to be fully elucidated. To this end, we performed small RNA sequencing on a human astrocytoma cell line to identify the complete repertoire of tRNA fragments generated by angiogenin. We found that only a specific subset of tRNAs are cleaved by angiogenin and identified 5’ValCAC tiRNA to be secreted from neural cells. 5’ValCAC was quantified in spinal cord and serum from SOD1G93A amyotrophic lateral sclerosis mouse models where we found it to be significantly elevated at symptom onset correlating with increased angiogenin expression, imbalanced protein translation initiation factors, and slower disease progression. In amyotrophic lateral sclerosis patient serum samples, we found 5’ValCAC to be significantly higher in patients with slow disease progression and interestingly we find 5’ValCAC to hold prognostic value for amyotrophic lateral sclerosis patients. Here we report that angiogenin cleaves a specific subset of tRNAs and provide evidence for 5’ValCAC as a prognostic biomarker in amyotrophic lateral sclerosis. We propose that increased serum 5’ValCAC levels indicate an enhanced angiogenin-mediated stress response within motor neurons that correlates with increased survival. These data suggest that the previously reported beneficial effects of angiogenin in SOD1G93A mice may result from elevated levels of 5’ValCAC tRNA fragment.

Potential of Non-Coding RNA as Biomarkers for Progressive Supranuclear Palsy

“…The function of tRNA fragments is still relatively unknown but they can be actively cleaved by angiogenin, have been shown to affect RNA translation and be induced by stress [ 30 , 31 ]. In fact, tRNA fragments have been proposed previously as biomarkers for ALS, including in our own studies [ 18 , 32 ]. Most interestingly though, one study, found that 5′ fragments derived from tRNA-ValCAC had elevated release from neural cells and cleavage in mouse models, and consequently had prognostic value when tested in human samples [ 32 ].…”

Emerging Roles of Non-Coding RNA in Neuronal Function and Dysfunction

“…Recent work has identified 5'tiRNA Val−CAC as a potential biomarker for ALS. This tiRNA was found to be increased in the spinal cord of SOD1 G93A mice and is significantly increased in the serum of patients with slow progressing ALS [120].…”

“…Interestingly, the Ang-generated tiRNA 5′ValCAC is increased in SOD1 G93A mice at symptom onset and correlate with Ang expression and slower disease progression. Furthermore, increased 5′ValCAC in ALS patient serum samples is correlated with slower disease progression [120].…”

Function and Therapeutic Implications of tRNA Derived Small RNAs

“…Initially, tiRs were found to be upregulated under various stress conditions, giving them the name stress-induced tRNA halves. The RNase IV enzyme, angiogenin (ANG), was identified to be the enzyme responsible for tiR production under stress conditions and the 5′-terminal oligoguanylate (TOG) motif was found to be present in these tiRs ( Ivanov et al, 2011 ; Saikia et al, 2014 ; Honda et al, 2015 ; Liu S. et al, 2018 ; Hogg et al, 2020 ). However, ANG KO does not reduce the levels of basally expressed (non-stress induced) tiRs ( Su et al, 2019 ).…”