Búsqueda y caracterización de sustratos fisiológicos de malina, la E3-ubiquitin ligasa implicada en la enfermedad de Lafora
- Autores: Lorena Kumarasinghe
- Directores de la Tesis: Pascual Sanz Bigorra (dir. tes.), Adelaida García Gimeno (codir. tes.)
- Lectura: En la Universitat de València ( España ) en 2023
- Idioma: español
- Número de páginas: 171
- Tribunal Calificador de la Tesis: Marta Casado Pinna (presid.), Carlos Romá Mateo (secret.), Marina Sánchez García (voc.)
- Programa de doctorado: Programa de Doctorado en Biomedicina y Biotecnología por la Universitat de València (Estudi General)
- Materias:
- Enlaces
- Tesis en acceso abierto en: TESEO
- Resumen
Lafora disease (LD) is a rare genetic disease that mainly affects adolescents and belongs to the group of diseases known as Progressive Myoclonus Epilepsies (PMEs). It is a fatal form of progressive myoclonus epilepsy and has an incidence of less than 4 cases in a million people worldwide. LD is caused by the accumulation of aberrant glycogen-like inclusions known as Lafora bodies (LBs), which are present in several tissues but are predominantly found in the brain. These LBs are insoluble and their aggregation leads to cellular toxicity, generating several progressive neurological symptoms, including difficult-to-control seizures, myoclonus, ataxia, dementia, and other symptoms. There is currently no definitive cure for LD, and treatment is mainly symptomatic and supportive, focusing on controlling seizures and managing other symptoms as they arise. The disease is caused by mutations that fall onto genes that codify for two different proteins: Laforin and Malin. These proteins have different functions but work in complex with each other.
My Ph.D. studies focused especially on Malin, known to be an E3 ubiquitin ligase which plays a major role in a process called ubiquitination. Therefore, Malin's activity makes LD a disease connected to the ubiquitin system. Several substrates of Malin have been identified to date, including those involved in the accumulation of polyglucosans, impairment in the degradation processes at the level of the proteasome and autophagy, alteration of glutamatergic transmission and mitochondrial dysfunction. However, many molecular mechanisms leading to these conditions need further elucidation. The hunt for novel substrates could help to identify previously unidentified dysfunctions of Lafora disease and to gain a better understanding of the aforementioned pathophysiological alterations. A proteomic analysis using the bioUb strategy identified 88 differentially ubiquitinated potential candidates involved in protein folding, heat shock response, and regulation of mitochondrial function. Two proteins, P-Rex1 and Hsp90 alpha, were chosen for further study due to their high ubiquitination rate and/or unique peptide number in the proteomic analysis. In this thesis, evidence will be reported in demonstrating how the first substrate is related to LD. We have validated the Malin-dependent ubiquitination of P-Rex1 and have focused on the effect of Malin on the function of P-Rex1 as a guanine-nucleotide exchange factor (GEF) in activating Rac1 GTPase and in increasing glucose uptake. The analysis conducted upon this substrate sets the genesis of the delineation of a molecular pathway that leads to altered glucose uptake, which could be one of the origins of the accumulation of the polyglucosans present in the disease.
Experiments conducted for Hsp90 alpha have validated it as a substrate of Malin, not only when it is overexpressed but also at endogenous level and, further on, we have hypothesized how it could possibly be related to the disease.
