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Background and Purpose –The mammalian target of rapamycin (mTOR) pathway has been implicated in cellular responses to hypoxia and inflammation. Cerebral palsy (CP) is a neurodevelopmental disorder often linked to hypoxic and inflammatory injury to the brain, however, a role for mTOR modulation in CP has not been investigated. We hypothesized that mTOR inhibition would prevent neuronal death and diminish inflammation in a mouse model of CP. Methods – Post-natal day 6 mouse pups were subjected to hypoxia-ischemia and lipopolysaccharide-induced inflammation (HIL), a model of CP causing injury to several brain areas. Mice received rapamycin (5mg/kg) following HIL, and then daily for 3 subsequent days. The phospho-activation of the mTOR effector mTOR effector proteins S6, S6K and 4EBP as well as upstream negative regulators, TSC1 and Redd1, were assessed as an in vivo measure of the mTOR signaling cascade. Expression of hypoxia inducible factor 1 (HIF-1 alpha) was assayed as an indicator of hypoxia-mediated cellular injury. Neuronal cell death was defined with Fluoro-Jade C (FJC) and cleaved-caspase 3 (CC3), a marker of apoptosis. Autophagy was measured using Beclin-1 and LC3II expression. Lastly, neuroninflammation following HIL was evaluated by examining Iba-1 labeled microglia number and morphology, as well as P-STAT3 expression. Results – Neuronal death, HIF-1alpha expression, and numerous Iba-1 labeled microglia were evident at 24 and 48 hours following HIL. Basal mTOR signaling was unchanged by HIL. Coincident with persistent mTOR signaling, a decreased in Redd1 expression but not TSC1 was observed in HIL. Increased P-STAT3 expression was observed at 24 and 48 hours post-HIL. Rapamycin treatment following HIL significantly reduced neuronal death, decreased HIF-1 alpha and P-STAT3 expression, and microglial activation, coincident with enhanced expression of Beclin-1 and LC3II, markers of autophagy induction. Increase in neuronal death was observed with concomitant administration of rapamycin and chloroquine, an autophagy inhibitor. Administration of a S6K inhibitor, PF-4708671, following HIL also decreased FJC staining further supporting an mTOR-dependent effect of HIL. Conclusions – mTOR inhibition prevented neuronal cell death and diminished neuroinflammation in this model of CP. Persistent mTOR signaling following HIL suggests a failure of autophagy induction, which may contribute to neuronal death in CP. These results suggest that mTOR signaling may be a novel therapeutic target to reduce neuronal cell death in CP. / Biomedical Neuroscience

In response to starvation, mis-folded proteins accumulate in the endoplasmic reticulum (E.R.) causing E.R. stress. This triggers a series of signaling pathways known as the unfolded protein response (UPR). The response helps to both enhance protein folding capacity and initiate mis-folded protein degradation, reducing E.R. stress. Alternatively, misfolded proteins are degraded and nutrients are recycled through autophagy. Thus, E.R. homeostasis depends on both UPR and autophagy. However, if E.R. stress is not resolved, UPR and autophagy can also cause apoptosis by mechanisms that are not fully understood. In chicken embryo fibroblasts, gamma-aminobutyric acid receptor-associated protein or GABARAP (a protein involved in autophagy) can promote apoptosis in conditions of prolonged starvation (Maynard et al. 2015). In these conditions, the down-regulation of GABARAP by shRNA/RNA interference reduces the expression of the pro-apoptotic CHOP (CAAT-enhancer-binding protein homologous protein) transcription factor (a marker of E.R. stress) and enhances cell survival. This suggests that elevated levels of autophagy compromises E.R. homeostasis and promotes the expression of CHOP in UPR lethal pathways. While GABARAP induction and processing/activation has been linked to the expression of CHOP upon prolonged starvation (Maynard et al. 2015), nothing is known about the pathway mediating CHOP expression and the relationship with other pathways of the UPR in cells with GABARAP mis-expression. Understanding these pathways will allow us to determine if GABARAP is a general determinant of E.R. stress or acts specifically on the expression of CHOP to control cell survival. Elucidating mechanisms which are involved in E.R. stress and the cellular transition between pro-survival to pro-apoptotic roles can allow understanding of processes associated with several pathological conditions like cancer and neuro-degenerative diseases. Additionally, establishing a role for GABARAP tumor suppressor in the control of the UPR and cell fate is also important. / Thesis / Bachelor of Science (BSc) / In response to starvation, mis-folded proteins accumulate in the endoplasmic reticulum (E.R.) causing E.R. stress. This activates both the Unfolded Protein Response (UPR) and Autophagy as both processes help to reduce E.R. stress. GABARAP, a protein involved in autophagy, has been shown to be involved in the promotion of apoptosis in conditions of prolonged starvation as its downregulation reduces apoptosis and CHOP expression (Maynard et al. 2015). However, how GABARAP regulates apoptosis remains unknown. Here, we investigate if GABARAP mis-expression affects multiple pathways in the UPR relieving global E.R. stress or if its specifically involved in blocking CHOP expression.

Lysosomal storage diseases (LSDs) are metabolic diseases which occur as a result of a deficiency of one of the essential lysosomal enzymes, called glycohydrolases. A mutation in the gene encoding one of these enzymes leads to an accumulation of unwanted substrates, resulting in a variety of clinical manifestations. A common symptom found in LSDs is skeletal muscle dysfunction, which includes muscle weakness, atrophy and loss of muscle mass. The genes for lysosomal hydrolases are well characterized; however, much less is known about how mutations in these genes affect the cell and lead to the muscle dysfunction observed. One pathway of interest is autophagy; it has been shown to be essential for maintenance of skeletal muscles. This study sought to investigate the impact of LSDs on autophagy and how this may potentiate muscle dysfunction. We utilized in-vivo and in-vitro models of Sialidosis, Sandhoff Disease, and GM1-Gangliosidosis in order to assess autophagy and its impact on myogenic differentiation in skeletal muscles. Our results demonstrated that autophagy is induced upstream (ULK1 phosphorylation) but is inhibited at the autophagosome to lysosome fusion (p62 upregulation) in LSDs. We also found that myoblast fusion and myogenic differentiation are impaired. We conclude that blocking autophagy impairs myogenic differentiation, which potentiates the muscle dysfunction observed in LSDs. This work highlights autophagy as a new pathway of interest and possible therapeutic target to alleviate muscle dysfunction in LSDs, and other similar neurodegenerative diseases. / Thesis / Master of Science (MSc) / Lysosomal storage diseases (LSDs) occur because of a deficiency of lysosomal glycohydrolases. A common symptom found in LSDs is skeletal muscle dysfunction. Little is known about how a deficiency of these enzymes leads to the clinical manifestations observed. However, one pathway of interest is autophagy. This study sought to investigate the impact of LSDs on autophagy and how this may potentiate muscle dysfunction. We utilized in-vivo and in-vitro models of LSDs to assess autophagy and its impact on myogenic differentiation in skeletal muscles. We demonstrated that autophagy is induced and blocked, and that myoblast fusion and myogenic differentiation is impaired. We concluded that the induction and block of autophagy impairs myogenic differentiation, which potentiates muscle dysfunction.

Wolbachia is a maternally transmitted intracellular bacterium estimated to infect 40% of insect species. Wolbachia manipulates the host’s reproduction to facilitate its own spread in nature. Transfection of Wolbachia strains from Drosophila melanogaster into mosquitoes can reduce the transmission of Dengue, Chikungunya, Zika and certain strains of the malaria parasite. Mosquitoes transmit these diseases because they require a blood meal to support egg production. Since every year approximately 1 million people die from mosquito-transmitted pathogens, the mosquito ovary can be considered one of the most dangerous organs to mankind. Nevertheless, little is known about early development of a mosquito egg, including the presence of active germline stem cells. In this thesis, through dual pulse experiments, we identify two cells that reside permanently at the anterior tip of the germarium and are actively dividing. Additional antibody labeling, presence of spectrosomes, 3D confocal reconstruction and scanning electron microscopy experiments confirm these cells as the germline stem cells and identify their respective niche. We also identified the somatic stem cells which give rise to the follicular epithelium, a cell type necessary for egg development. Characterization of Wolbachia infected mosquito ovaries displayed high density in the germline, but low density in the surrounding somatic cells. High Wolbachia densities correlate with reduced pathogen transmission. Host autophagy possibly affects Wolbachia intracellular density. Autophagy is an intracellular degradation pathway involved in innate immunity against bacteria and viruses. The literature suggests that autophagy positively regulates Wolbachia in the germline and negatively in somatic cells. We utilized genetic manipulations of several autophagy genes to determine that a selective form of autophagy in somatic cells negatively regulates Wolbachia, while a non-selective form positively regulates Wolbachia in the germline. Furthermore, we find that Wolbachia effectors can regulate Wolbachia density through the autophagy pathway. In the germline we utilize global metabolomics of autophagy mutants to identify candidate pathways that can positively influence Wolbachia density. These results provide novel insights into the mechanisms of Wolbachia – host autophagy interactions. / 2022-03-17T00:00:00Z

Yes / Glioblastoma multiforme (GBM) is a grade IV brain tumor characterized by a heterogeneous population of cells that are highly infiltrative, angiogenic and resistant to chemotherapy. The current standard of care, comprised of surgical resection followed by radiation and the chemotherapeutic agent temozolomide, only provides patients with a 12–14 month survival period post-diagnosis. Long-term survival for GBM patients remains uncommon as cells with intrinsic or acquired resistance to treatment repopulate the tumor. In this review we will describe the mechanisms of resistance, and how they may be overcome to improve the survival of GBM patients by implementing novel chemotherapy drugs, new drug combinations and new approaches relating to DNA damage, angiogenesis and autophagy.