Traumatic injury induces stress granule formation and enhances motor dysfunctions in ALS/FTD models

Abstract

Traumatic brain injury (TBI) has been predicted to be a predisposing factor for amyotrophic lateral sclerosis (ALS) and other neurological disorders. Despite the importance of TBI in ALS progression, the underlying cellular and molecular mechanisms are still an enigma. Here, we examined the contribution of TBI as an extrinsic factor and investigated whether TBI influences the susceptibility of developing neurodegenerative symptoms. To evaluate the effects of TBI in vivo, we applied mild to severe trauma to Drosophila and found that TBI leads to the induction of stress granules (SGs) in the brain. The degree of SGs induction directly correlates with the level of trauma. Furthermore, we observed that the level of mortality is directly proportional to the number of traumatic hits. Interestingly, trauma-induced SGs are ubiquitin, p62 and TDP-43 positive, and persistently remain over time suggesting that SGs might be aggregates and exert toxicity in our fly models. Intriguingly, TBI on animals expressing ALS-linked genes increased mortality and locomotion dysfunction suggesting that mild trauma might aggravate neurodegenerative symptoms associated with ALS. Furthermore, we found elevated levels of high molecular weight ubiquitinated proteins and p62 in animals expressing ALS-causing genes with TBI, suggesting that TBI may lead to the defects in protein degradation pathways. Finally, we observed that genetic and pharmacological induction of autophagy enhanced the clearance of SGs and promoted survival of flies in vivo. Together, our study demonstrates that trauma can induce SG formation in vivo and might enhance neurodegenerative phenotypes in the fly models of ALS.

Small molecule modulation of a redox-sensitive stress granule protein dissolves stress granules with beneficial outcomes for familial amyotrophic lateral sclerosis models

“…Climbing assays were performed as previously described 80 For stressed cells treated with 15 N R-(+)-lipoamide the high signal intensity from the washed cell sample (green) is consistent with the large uptake from the medium calculated from the with (red) and without cell (cyan) signal intensity. d) Quantitation of c) showing percentage uptake and calculated intracellular concentration, assuming that lipoamide is uniformly distributed within cells (see Supplemental Methods).…”

“…The w1118, UAS-eGFP, and D42-GAL4 were obtained from Bloomington stock center. The UAS-FUS WT, UAS-FUS P525L, and UAS-FUS R521C were previously described 80 .…”

Expansion of a fly TBI model to four levels of injury severity reveals synergistic effects of repetitive injury for moderate injury conditions

“…We determined geotaxis performance by measuring the distance traveled by each fly 5 seconds and 10 seconds after startle, which were similar time-points to previous literature (Gargano et al 2005; Linderman et al 2012; Podratz et al 2013; Anderson et al 2018). All conditions showed improved scores at 10 s compared to 5 s (Fig.…”

“…Flies are well-known to exhibit motor dysfunction following TBI (Katzenberger et al 2013; Barekat et al 2016; Anderson et al 2018). However, the time-course of motor dysfunction across the primary and secondary injury periods, and for TBI of varying severities is not well-characterized.…”

“…Two models for studying TBI have been developed for the fruit fly ( Drosophila melanogaster ): the high-impact trauma (HIT) method, which uses a spring-based device deflected to 90°, and the Bead Ruptor homogenizer method, which uses a programmable homogenizer that can be set to various speeds and durations (Katzenberger et al 2013; Barekat et al 2016). Importantly, use of each method results in classic post-TBI symptoms including impaired locomotion, shortened lifespan, neurodegeneration, intestinal barrier disruption, and activation of immune and autophagy processes (Katzenberger et al 2013; Barekat et al 2016; Anderson et al 2018). While the Bead Ruptor method offers potential advantages in the ease of scaling primary injuries and inter-experiment standardization, the HIT method is simple, cost-effective, and better characterized to date (Katzenberger et al 2013, 2015, 2016; Barekat et al 2016; Anderson et al 2018).…”