New insights on the pathomechanism of GNE myopathy: proposing an immune-mediated response

• Autor(a) principal: Pereira, Beatriz Luís
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/154801
• topic: Glycosylation; Sialic acid; Congenital Disorders of Glycosylation; GNE myopathy; Biomarkers; Prodrugs; Domínio/Área Científica::Engenharia e Tecnologia::Outras Engenharias e Tecnologias

Glycosylation is known to be involved in several biological functions, and defects in the synthesis or attachment of sugars can modulate the course of various malignancies. GNE myopathy (GNEM) is an ultra-rare congenital disorder of glycosylation caused by biallelic mutations in the GNE gene, which encodes for a bifunctional enzyme required for sialic acid biosynthesis. Although, hyposialylation has been assumed as the main cause of this myopathy, new data suggest that GNEM mechanism is far more complicated. To date, there is no approved treatment for GNEM and research on sialylation-increasing therapies is challenged by unknown processes and the absence of biomarkers. In this work we explored cellular and molecular mechanisms that may contribute to this myopathy as a means of identifying alternative therapeutic targets and biomarkers. Previous studies have identified that sialic acid removal alters the expression of some immune agents; this led us to study whether defective sialylation in the GNE knock-out cell model influences immune function. The overexpression of major histocompatibility complex class-I (MHC-I) and cytokine secretion levels in GNEM cell model point towards the involvement of an immune response and suggest that immune players could be good disease biomarkers in diagnostic and clinical development. Furthermore, drug-likeliness of newly synthesized compounds (based on prodrug technology) was computationally analysed, and assays to evaluate the in vitro toxicity and efficacy of the prodrugs were designed and optimized, using N-acetyl-D-mannosamine currently in phase 2 of clinical trials and N-acetyl-D-mannosamine-6-phosphate (parent compound). Although no restoring of the sialic acid content was observed with both compounds, a small recovery of immune parameters suggests the involvement of pathways other than sialylation. Overall, understanding the immune response in GNEM could bring some light into pathophysiology and accelerate the approval of a new therapeutic option.