Truncated Analogues of a G-Quadruplex-Forming Aptamer Targeting Mutant Huntingtin: Shorter Is Better!

Two analogues of the MS3 aptamer, which was previously shown to have an exquisite capability to selectively bind and modulate the activity of mutant huntingtin (mHTT), have been here designed and evaluated in their physicochemical and biological properties. Featured by a distinctive propensity to form complex G-quadruplex structures, including large multimeric aggregates, the original 36-mer MS3 has been truncated to give a 33-mer (here named MS3-33) and a 17-mer (here named MS3-17). A combined use of different techniques (UV, CD, DSC, gel electrophoresis) allowed a detailed physicochemical characterization of these novel G-quadruplex-forming aptamers, tested in vitro on SH-SY5Y cells and in vivo on a Drosophila Huntington's disease model, in which these shorter MS3-derived oligonucleotides proved to have improved bioactivity in comparison with the parent aptamer.

The Reversible Carnitine Palmitoyltransferase 1 Inhibitor (Teglicar) Ameliorates the Neurodegenerative Phenotype in a Drosophila Huntington's Disease Model by Acting on the Expression of Carnitine-Related Genes.

Huntington's disease (HD) is a dramatic neurodegenerative disorder caused by the abnormal expansion of a CAG triplet in the huntingtin gene, producing an abnormal protein. As it leads to the death of neurons in the cerebral cortex, the patients primarily present with neurological symptoms, but recently metabolic changes resulting from mitochondrial dysfunction have been identified as novel pathological features. The carnitine shuttle is a complex consisting of three enzymes whose function is to transport the long-chain fatty acids into the mitochondria. Here, its pharmacological modification was used to test the hypothesis that shifting metabolism to lipid oxidation exacerbates the HD symptoms. Behavioural and transcriptional analyses were carried out on HD Drosophila model, to evaluate the involvement of the carnitine cycle in this pathogenesis. Pharmacological inhibition of CPT1, the rate-limiting enzyme of the carnitine cycle, ameliorates the HD symptoms in Drosophila, likely acting on the expression of carnitine-related genes.

Fighting the Huntington's Disease with a G-Quadruplex-Forming Aptamer Specifically Binding to Mutant Huntingtin Protein: Biophysical Characterization, In Vitro and In Vivo Studies.

A set of guanine-rich aptamers able to preferentially recognize full-length huntingtin with an expanded polyglutamine tract has been recently identified, showing high efficacy in modulating the functions of the mutated protein in a variety of cell experiments. We here report a detailed biophysical characterization of the best aptamer in the series, named MS3, proved to adopt a stable, parallel G-quadruplex structure and show high nuclease resistance in serum. Confocal microscopy experiments on HeLa and SH-SY5Y cells, as models of non-neuronal and neuronal cells, respectively, showed a rapid, dose-dependent uptake of fluorescein-labelled MS3, demonstrating its effective internalization, even in the absence of transfecting agents, with no general cytotoxicity. Then, using a well-established Drosophila melanogaster model for Huntington's disease, which expresses the mutated form of human huntingtin, a significant improvement in the motor neuronal function in flies fed with MS3 was observed, proving the in vivo efficacy of this aptamer.

L-Carnitine in Drosophila: A Review.

L-Carnitine is an amino acid derivative that plays a key role in the metabolism of fatty acids, including the shuttling of long-chain fatty acyl CoA to fuel mitochondrial ß-oxidation. In addition, L-carnitine reduces oxidative damage and plays an essential role in the maintenance of cellular energy homeostasis. L-carnitine also plays an essential role in the control of cerebral functions, and the aberrant regulation of genes involved in carnitine biosynthesis and mitochondrial carnitine transport in Drosophila models has been linked to neurodegeneration. Drosophila models of neurodegenerative diseases provide a powerful platform to both unravel the molecular pathways that contribute to neurodegeneration and identify potential therapeutic targets. Drosophila can biosynthesize L-carnitine, and its carnitine transport system is similar to the human transport system; moreover, evidence from a defective Drosophila mutant for one of the carnitine shuttle genes supports the hypothesis of the occurrence of ß-oxidation in glial cells. Hence, Drosophila models could advance the understanding of the links between L-carnitine and the development of neurodegenerative disorders. This review summarizes the current knowledge on L-carnitine in Drosophila and discusses the role of the L-carnitine pathway in fly models of neurodegeneration.