Genetic activation of parkin rescues TAF15-induced neurotoxicity in a Drosophila model of amyotrophic lateral sclerosis

Reduced oxidative stress suppresses neurotoxicity in the Drosophila model of TAF15-associated proteinopathies

TATA-binding protein associated factor 15 (TAF15) is involved in the pathology of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Although TAF15 accumulates as cytoplasmic aggregates in neurons and the clearance of aggregates may be a therapeutic strategy for ALS, the underlying mechanisms of TAF15 in ALS remain poorly understood. Recently, we found that glutathione transferase omega 2 (GstO2) expression level is significantly reduced in the brain tissue of TAF15-expressing flies. In this study, we demonstrated that GstO2 overexpression in TAF15-induced flies rescues the locomotive activity and neuromuscular junctional defects. Furthermore, TAF15 levels in both cytoplasm and nuclear fractions significantly decreased in the heads of GstO2 co-expressing flies. GstO2-co-overexpression in neurons caused a marked decrease in intracellular reactive oxygen species generation in TAF15-induced flies. Our findings demonstrated that GstO2 was a pathogenic regulator of TAF15-associated proteinopathies. They help expand our understanding of TAF15-associated ALS pathogenesis.

FUS-induced neurotoxicity is prevented by inhibiting GSK-3β in a drosophila model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS)-linked mutations in fused in sarcoma (FUS) lead to the formation of cytoplasmic aggregates in neurons. They are believed play a critical role in the pathogenesis of FUS-associated ALS. Therefore, the clearance and degradation of cytoplasmic FUS aggregates in neurons may be considered a therapeutic strategy for ALS. However, the molecular pathogenic mechanisms behind FUS-associated ALS remain poorly understood. Here, we report GSK-3β as a potential modulator of FUS-induced toxicity. We demonstrated that RNAi-mediated knockdown of Drosophila ortholog Shaggy in FUS-expressing flies suppresses defective phenotypes, including retinal degeneration, motor defects, motor neuron degeneration, and mitochondrial dysfunction. Furthermore, we found that cytoplasmic FUS aggregates were significantly reduced by Shaggy knockdown. In addition, we found that the levels of FUS proteins were significantly reduced by co-overexpression of Slimb, a F-box protein, in FUS-expressing flies, indicating that Slimb is critical for the suppressive effect of Shaggy/GSK-3β inhibition on FUS-induced toxicity in Drosophila. These findings revealed a novel mechanism of neuronal protective effect through SCFSlimb-mediated FUS degradation via GSK-3β inhibition, and provided in vivo evidence of the potential for modulating FUS-induced ALS progression using GSK-3β inhibitors.

SCF-Slimb is critical for Glycogen synthase kinase-3β-mediated suppression of TAF15-induced neurotoxicity in Drosophila

Amyotrophic lateral sclerosis (ALS) is a severe neurodegenerative disorder characterized pathologically by motor neuron degeneration and associated with aggregation of RNA-binding proteins. TATA-binding protein-associated factor 15 (TAF15) accumulates as cytoplasmic aggregates in neuronal cells, and clearance of these aggregates is considered a potential therapeutic strategy for ALS. However, the exact pathogenic mechanism of TAF15-induced neurotoxicity remains to be elucidated. Glycogen synthase kinase-3 (GSK-3) plays a critical role in the protection of ALS pathology. In the present study, we use a transgenic fly model over-expressing human TAF15 to study the protective effects of Shaggy/GSK3β on TAF15-induced neuronal toxicity in Drosophila brain. Transgenic flies were examined for locomotor activity and lithium treatment. The expression level and solubility of TAF15 were assessed with western blotting, whereas immunohistochemistry was used to assess TAF15 aggregation in Drosophila brain. We have revealed that Shaggy/GSK3β was abnormally activated in neurons of TAF15-expressing flies and its inhibition can suppress the defective phenotypes, thereby preventing retinal degeneration and locomotive activity caused by TAF15. We have also found that Shaggy/GSK3β inhibition in neuronal cells leads to a reduction in TAF15 levels. Indeed, the F-box proteins Slimb and archipelago genetically interact with TAF15 and control TAF15 protein level in Drosophila. Importantly, SCF^slimb is a critical regulator for Shaggy/GSK3β-mediated suppression of TAF15-induced toxicity in Drosophila. The present study has provided an in vivo evidence supporting the molecular mechanism of GSK3β inhibition for protection against TAF15-linked proteinopathies.

Parkin expression reverses mitochondrial dysfunction in fused in sarcoma-induced amyotrophic lateral sclerosis

Fused in sarcoma (FUS) is a DNA/RNA-binding protein associated with amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration. The exact molecular mechanisms by which FUS results in neurotoxicity have not yet been fully elucidated. Here, we found that parkin is a genetic suppressor of defective phenotypes induced by exogenous human wild type FUS in Drosophila. Although parkin overexpression did not modulate the FUS protein expression level, the locomotive defects in FUS-expressing larvae and adult flies were rescued by parkin expression. We found that FUS expression in muscle tissues resulted in a reduction of the levels and assembly of mitochondrial complex I and III subunits, as well as decreased ATP. Remarkably, expression of parkin suppressed these mitochondrial dysfunctions. Our results indicate parkin as a neuroprotective regulator of FUS-induced proteinopathy by recovering the protein levels of mitochondrial complexes I and III. Our findings on parkin-mediated neuroprotection may expand our understanding of FUS-induced ALS pathogenesis.

Human Papillomavirus Epitope Mimicry and Autoimmunity: The Molecular Truth of Peptide Sharing

OBJECTIVE

To define the cross-reactivity potential and the consequent autoimmunity intrinsic to viral versus human peptide sharing.

METHODS

Using human papillomavirus (HPV) infection/active immunization as a research model, the experimentally validated HPV L1 epitopes catalogued at the Immune Epitope DataBase were analyzed for peptide sharing with the human proteome.

RESULTS

The final data show that the totality of the immunoreactive HPV L1 epi-topes is mostly composed by peptides present in human proteins.

CONCLUSIONS

Immunologically, the high extent of peptide sharing between the HPV L1 epitopes and human proteins invites to revise the concept of the negative selection of self-reactive lymphocytes. Pathologically, the data highlight a cross-reactive potential for a spectrum of autoimmune diseases that includes ovarian failure, systemic lupus erythematosus (SLE), breast cancer and sudden death, among others. Therapeutically, analyzing already validated immunoreactive epitopes filters out the peptide sharing possibly exempt of self-reactivity, defines the effective potential for pathologic autoimmunity, and allows singling out peptide epitopes for safe immunotherapeutic protocols.