MicroRNA miR-1002 Enhances NMNAT-Mediated Stress Response by Modulating Alternative Splicing

Abstract

SummaryUnderstanding endogenous regulation of stress resistance and homeostasis maintenance is critical to developing neuroprotective therapies. Nicotinamide mononucleotide adenylyltransferase (NMNAT) is a conserved essential enzyme that confers extraordinary protection and stress resistance in many neurodegenerative disease models. Drosophila Nmnat is alternatively spliced to two mRNA variants, RA and RB. RB translates to protein isoform PD with robust protective activity and is upregulated upon stress to confer enhanced neuroprotection. The mechanisms regulating the alternative splicing and stress response of NMNAT remain unclear. We have discovered a Drosophila microRNA, dme-miR-1002, which promotes the splicing of NMNAT pre-mRNA to RB by disrupting a pre-mRNA stem-loop structure. NMNAT pre-mRNA is preferentially spliced to RA in basal conditions, whereas miR-1002 enhances NMNAT PD-mediated stress protection by binding via RISC component Argonaute1 to the pre-mRNA, facilitating the splicing switch to RB. These results outline a new process for microRNAs in regulating alternative splicing and modulating stress resistance.

MicroRNA-Mediated Obstruction of Stem-loop Alternative Splicing (MIMOSAS): a global mechanism for the regulation of alternative splicing

“…Previously, we found that miR-1002 potentially binds and interferes with a splicerelevant stem loop formation on the Nmnat pre-mRNA that distinguished between splice variants RA and RB (28). Notably, we corroborated our predictions by expressing miR-1002 that led to the expected shift toward the predicted neuroprotective splice variant RB and away from RA.…”

“…Based on the assumption that the duplex of the binding microRNA and mRNA is (i) located at the stem of a hairpin loop and is (ii) energetically more favorable than the formation of the stem loop itself, we predicted that miR-1002 potentially interfered with a splice-relevant stem loop formation on the Nmnat mRNA that regulated the different splice variants RA and RB. Most notably, we corroborated our computational prediction by experimentally over-expressing miR-1002 that led to the predicted shift of the predicted neuroprotective splice variant RB of the Nmnat gene away from RA (28).…”

AGFPsplicing reporter in acoilinmutant background reveals links between alternative splicing, siRNAs and coilin function inArabidopsis thaliana

“…These processes require in some cases small RNAs. (Wang et al, 2015; Kishore et al, 2010; Park et al, 2019; Wang and Chekanova, 2016; Preuss et al, 2008; Huang et al, 2022). The identification of zc3hc1 mutations in the coi1 suppressor screen and their enhancement of GFP siRNA accumulation provide at least an indirect link between coilin function and siRNA biogenesis and/or stability.…”