Mutant Ataxin-3-Containing Aggregates (MATAGGs) in Spinocerebellar Ataxia Type 3: Dynamics of the Disorder

Transgenic sensors reveal compartment-specific effects of aggregation-prone proteins on subcellular proteostasis during aging

Loss of proteostasis is a hallmark of aging that underlies many age-related diseases. Different cell compartments experience distinctive challenges in maintaining protein quality control, but how aging regulates subcellular proteostasis remains underexplored. Here, by targeting the misfolding-prone FlucDM luciferase to the cytoplasm, mitochondria, and nucleus, we established transgenic sensors to examine subcellular proteostasis in Drosophila. Analysis of detergent-insoluble and -soluble levels of compartment-targeted FlucDM variants indicates that thermal stress, cold shock, and pro-longevity inter-organ signaling differentially affect subcellular proteostasis during aging. Moreover, aggregation-prone proteins that cause different neurodegenerative diseases induce a diverse range of outcomes on FlucDM insolubility, suggesting that subcellular proteostasis is impaired in a disease-specific manner. Further analyses with FlucDM and mass spectrometry indicate that pathogenic tauV337M produces an unexpectedly complex regulation of solubility for different FlucDM variants and protein subsets. Altogether, compartment-targeted FlucDM sensors pinpoint a diverse modulation of subcellular proteostasis by aging regulators.

A combination of chlorzoxazone and folic acid improves recognition memory, anxiety and depression in SCA3-84Q mice

Spinocerebellar ataxia type 3 (SCA3), also known as Machado-Joseph disease, is reported to be the most common type of autosomal dominant cerebellar ataxia (ADCA). SCA3 patients suffer from a progressive decline in motor coordination and other disease-associated symptoms. Moreover, recent studies have reported that SCA3 patients also exhibit symptoms of cerebellar cognitive affective syndrome (CCAS). We previously observed signs of CCAS in mouse model of SCA3. Particularly, SCA3-84Q mice suffer from anxiety, recognition memory decline, and also exhibit signs of low mood and aversion to activity. Here we studied the effect of long-term injections of SK channels activator chlorzoxazone (CHZ) together and separately with the folic acid (FA) on the cerebellar Purkinje cell (PC) firing and histology, and also on the motor and cognitive functions as well as mood alterations in SCA3-84Q hemizygous transgenic mice. We realized that both CHZ and CHZ-FA combination had similar positive effect on pure cerebellum impairments including PC firing precision, PC histology, and motor performance in SCA3-84Q mice. However, only the CHZ-FA combination, but not CHZ, had significantly ameliorated the signs of anxiety and depression, and also noticeably improved recognition memory in SCA3-84Q mice. Our results suggest that the combination therapy for both ataxia and non-motor symptoms is required for the complex treatment of ADCA.

Polyglutamine disorders: Pathogenesis and potential drug interventions

Polyglutamine/poly(Q) diseases are a group nine hereditary neurodegenerative disorders caused due to abnormally expanded stretches of CAG trinucleotide in functionally distinct genes. All human poly(Q) diseases are characterized by the formation of microscopically discernable poly(Q) positive aggregates, the inclusion bodies. These toxic inclusion bodies are responsible for the impairment of several cellular pathways such as autophagy, transcription, cell death, etc., that culminate in disease manifestation. Although, these diseases remain largely without treatment, extensive research has generated mounting evidences that various events of poly(Q) pathogenesis can be developed as potential drug targets. The present review article briefly discusses the key events of disease pathogenesis, model system-based investigations that support the development of effective therapeutic interventions against pathogenesis of human poly(Q) disorders, and a comprehensive list of pharmacological and bioactive compounds that have been experimentally shown to alleviate poly(Q)-mediated neurotoxicity. Interestingly, due to the common cause of pathogenesis, all poly(Q) diseases share etiology, thus, findings from one disease can be potentially extrapolated to other poly(Q) diseases as well.

CircHIPK3 negatively regulates autophagy by blocking VCP binding to the Beclin 1 complex in bladder cancer

Circular RNA HIPK3 (circHIPK3) mediates the progression of multiple cancers, including bladder cancer, by regulating cell migration, autophagy and epithelial mesenchymal transition. However, the mechanism by which circHIPK3 regulates autophagy in bladder cancer cells remains unclear. Autophagy is a common self-protection mechanism in eukaryotic cells and is essential for cell survival and death regulation. However, it is unclear whether circHIPK3 affects the level of autophagy in bladder cancer through binding proteins, and the potential regulatory mechanism is unknown. Here, we found that circHIPK3 levels were significantly lower and autophagy-related proteins were significantly upregulated in bladder cancer cells and tissues compared to normal controls. CircHIPK3 downregulation promoted bladder cancer cell proliferation, while circHIPK3 overexpression inhibited proliferation. CircHIPK3 overexpression significantly suppressed autophagy in bladder cancer cells. Overexpression of circHIPK3 did not affect VCP protein expression but inhibited the VCP/Beclin 1 interaction. VCP also stabilized Beclin 1 and promoted autophagy in bladder cancer cells by downregulating ataxin-3. Thus, circHIPK3 may play an important role in bladder cancer by inhibiting VCP-mediated autophagy.

Glipizide ameliorates human poly(Q) mediated neurotoxicity by upregulating insulin signalling in Drosophila disease models

Increasing reports suggest insulin signalling pathway as a putative drug target against polyglutamine [poly(Q)] disorders, such as Huntington's disease (HD), Spinocerebellar ataxias (SCA) 1, 2, 3 etc. However, studies on drug-based stimulation of insulin signalling cascade to mitigate poly(Q) pathogenesis are lacking. In our study, we adopted an evidence-based approach to examine if some established insulin stimulating drug can be utilized to restrict poly(Q) aetiology in Drosophila disease models. For the first time, we report that glipizide, an FDA approved anti-diabetic drug upregulates insulin signalling in poly(Q) expressing tissues and restricts formation of inclusion bodies and neurodegeneration. Moreover, it reinstates the chromatin architecture by improving histone acetylation, which is otherwise abrogated due to poly(Q) toxicity. In view of the functional conservation of insulin signalling pathway in Drosophila and humans, our finding strongly suggests that glipizide can be repurposed as an effective treatment strategy against the neurodegenerative poly(Q) disorders. Also, with appropriate validation studies in mammalian disease models, glipizide could be subsequently considered for the clinical trials in human patients.