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Browsing by Subject "proximity-dependent labelling"

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  • Sorri, Selma (2022)
    Diffuse large B-cell lymphoma (DLBCL) represents the most common diagnostic entity of lymphoid malignancies. As only 60% of the patients are cured with the current standard of care R-CHOP immunochemotherapy, the quest for better biomarkers and targeted therapies continues. Non-synonymous mutations in the WWE1 domain of an uncharacterized E3 ubiquitin ligase Deltex-1 have been associated with poor outcomes in DLBCL patients. Thus, to elucidate molecular features underlying this observation, this Master’s thesis set out to characterize the expression and subcellular localization of Deltex-1 in a panel of DLBCL cell lines, and to investigate the interaction partners of Deltex-1 in the activated B-cell like (ABC) DLBCL cell line context. The study aimed to gain further knowledge to understand the role that Deltex-1 plays in the pathogenesis of DLBCL, which could be used for inspecting its future possibilities as a prognostic marker or a drug target. Western blot analysis of the cell lysates revealed variable levels of Deltex-1 expression, especially between the ABC-DLBCL cell lines in comparison to germinal centre B-cell like (GCB) DLBCL cell lines. Western blots of separate cytoplasmic and nuclear fractions of the cells showed that Deltex-1 was expressed both in the cytoplasmic and the nuclear fractions of the cells, and the expression levels were reflecting the levels of the whole cell lysates of the same cell lines. The more exact localization of Deltex-1 was observed with immunofluorescence staining and microscopy of fixed cells from a few chosen cell lines. A distinct plasma membrane localization was detected in an ABC-DLBCL cell line U2932. The protein-protein interaction partners of Deltex-1 in the U2932 cell line were screened using proximity-dependent biotin labelling and affinity purification mass spectrometry. The experiments revealed novel associations between Deltex-1 and B-cell receptor signalling regulators, such as B- lymphocyte antigen CD20 and tyrosine protein kinase Lck. Though additional research is needed to define the functional mechanisms of these interactions, these findings might lead to the discovery of the connection between Deltex-1 and lymphomagenesis. In conclusion, this study provides novel information on Deltex-1 expression in the DLBCL context and describes previously unidentified associations of Deltex-1 with B-cell receptor signalling. Yet, more functional experiments are required to clarify the nature of these interactions.