The autophagy protein Def8 is altered in Alzheimer's disease and Aß42-expressing Drosophila brains.

Alzheimer's disease (AD) is the most common neurodegenerative disorder, characterized by protein accumulation in the brain as a main neuropathological hallmark. Among them, Aß42 peptides tend to aggregate and create oligomers and plaques. Macroautophagy, a form of autophagy characterized by a double-membrane vesicle, plays a crucial role in maintaining neuronal homeostasis by degrading protein aggregates and dysfunctional organelles as a quality control process. Recently, DEF8, a relatively uncharacterized protein, has been proposed as a participant in vesicular traffic and autophagy pathways. We have reported increased DEF8 levels in lymphocytes from mild cognitive impairment (MCI) and early-stage AD patients and a neuronal profile in a murine transgenic AD model. Here, we analyzed DEF8 localization and levels in the postmortem frontal cortex of AD patients, finding increased levels compared to healthy controls. To evaluate the potential function of DEF8 in the nervous system, we performed an in silico assessment of its expression and network profiles, followed by an in vivo evaluation of a neuronal Def8 deficient model using a Drosophila melanogaster model of AD based on Aß42 expression. Our findings show that DEF8 is an essential protein for maintaining cellular homeostasis in the nervous system, and it is upregulated under stress conditions generated by Aß42 aggregation. This study suggests DEF8 as a novel actor in the physiopathology of AD, and its exploration may lead to new treatment avenues.

Antisense noncoding mitochondrial RNA-2 gives rise to miR-4485-3p by Dicer processing in vitro.

BACKGROUND: The antisense noncoding mitochondrial RNAs (ASncmtRNAs) derive from the mitochondrial 16S gene. Knockdown of these transcripts with chemically-modified antisense oligonucleotides induces proliferative arrest, apoptosis and invasiveness reduction in tumor but not normal cells. One of these transcripts, ASncmtRNA-2, contains the complete and identical sequence of hsa-miR-4485-3p and, upon knockdown of this transcript, there is a strong increase in levels of this miRNA, suggesting ASncmtRNA-2 as a source for miR-4485-3p, which is supported by several evidences from our group and others, in the ex vivo setting. RESULTS: Here we show that incubation of in vitro-transcribed ASncmtRNA-2 with recombinant Dicer produces RNA fragments corresponding to hsa-miR-4485-3p, showing that Dicer binds to and processes ASncmtRNA-2, strongly supporting the hypothesis that ASncmtRNA-2 acts as a precursor for miR-4485-3p. CONCLUSION: The in vitro results presented here strengthen the hypothesis that miR-4485-3p is derived from ASncmtRNA-2 by Dicer processing. Since miR-4485-3p is classified as a tumor suppressor miRNA, this evidence strengthens the application of ASncmtRNA knockdown for cancer therapy.

Antisense noncoding mitochondrial RNA-2 gives rise to miR-4485-3p by Dicer processing in vitro

BACKGROUND: The antisense noncoding mitochondrial RNAs (ASncmtRNAs) derive from the mitochondrial 16S gene. Knockdown of these transcripts with chemically-modified antisense oligonucleotides induces proliferative arrest, apoptosis and invasiveness reduction in tumor but not normal cells. One of these transcripts, ASncmtRNA-2, contains the complete and identical sequence of hsa-miR-4485-3p and, upon knockdown of this transcript, there is a strong increase in levels of this miRNA, suggesting ASncmtRNA-2 as a source for miR-4485-3p, which is supported by several evidences from our group and others, in the ex vivo setting. RESULTS: Here we show that incubation of in vitro-transcribed ASncmtRNA-2 with recombinant Dicer produces RNA fragments corresponding to hsa-miR-4485-3p, showing that Dicer binds to and processes ASncmtRNA-2, strongly supporting the hypothesis that ASncmtRNA-2 acts as a precursor for miR-4485-3p. CONCLUSION: The in vitro results presented here strengthen the hypothesis that miR-4485-3p is derived from ASncmtRNA-2 by Dicer processing. Since miR-4485-3p is classified as a tumor suppressor miRNA, this evidence strengthens the application of ASncmtRNA knockdown for cancer therapy.