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  • Hlutverk sjálfsáts próteinsins ATG7 í blóði
  • Titill er á ensku The role of the autophagy protein ATG7 in blood
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  • Útdráttur er á ensku

    Autophagy, or “self-eating”, is an essential and highly conserved self-degradative process found in all eukaryotic cells. There are three main types of autophagy: macroautophagy, microautophagy and chaperone-mediated autophagy. Macroautophagy is the most common pathway and therefore the most studied. Autophagy is a cellular recycling process, valuable for maintaining cellular- and organismal homeostasis, through the removal of excessive or impaired cellular components in autophagosomes that fuse with lysosomes where they are broken down by lysosomal enzymes. While important for cellular quality control, autophagy is vital under various stressors including starvation, where unnecessary components are degraded for reuse in anabolic biosynthetic pathways. The accumulation of misfolded or aggregated proteins, damaged mitochondria or other organelles elevates oxidative stress, promoting chronic inflammation and genomic instability. Therefore, dysfunctions in the mechanism of autophagy are linked with the pathogenesis of several neurodegenerative, infectious, and metabolic diseases including Alzheimer, Parkinson’s, insulin resistance, diabetes, and cancer. Autophagy is a double-edged sword with regards to cancer where the process initially protects against tumorigenesis. However, tumor cells can utilize autophagy to sustain growth and to promote immune evasion.
    Autophagy related protein 7, ATG7, is required for autophagy where it facilitates the expansion of the phagophore through the lipidation of LC3/GABARAPs as an E1-like activating enzyme. A smaller isoform, termed ATG7(2), lacks one exon encoding 27 amino acids and as a result, loses its best characterized function that is to bind to and lipidate LC3/GABARAPs. The mRNA expression of total ATG7 increases in primary tumor tissue compared to normal tissue, and even more in metastatic tissue, where the increase is mainly driven by a higher expression of the smaller isoform, ATG7(2). Overall, the larger isoform, ATG7(1), is mainly expressed in every tissue, except for a clear shift in isoform expression in normal blood tissue. However, whether the smaller isoform is expressed on a protein level remains to be elucidated. Autophagy and ATG7 are known to be essential for the hematopoietic system for normal differentiation of cells, in addition to various immune functions including phagocytosis, degranulation and the mediation of inflammation.
    The main objective of this project was to study the endogenous protein expression levels of the smaller isoform and its physiological function in blood. Bioinformatic analysis with publicly available data from online databanks revealed cell types with the highest expression of ATG7 while enrichment analysis presented the according biological processes. Two valuable tools were generated to characterize the function of ATG7 in blood, one being the isoform specific siRNA for the larger isoform ATG7(1), and the other stable HL-60 cell lines with inducible overexpression of each isoform. To explore ATG7 protein isoform expression and protein-protein interaction (PPI) in blood cells, co-Immunoprecipitated ATG7 protein samples were generated from primary blood cells with the highest expression of ATG7, monocytes and neutrophils, for mass spectrometry analysis. Finally, existing mass spectrometry data on the PPI of ATG7 isoforms in Huh7 and MEF (mouse embryonic fibroblast) cells were further analyzed to explore the possible role of ATG7 in blood.

  • Rannís
  • 8.6.2022

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