miR-181c Modulates T Cell Function By Regulating the Expression of BRK1

    Student thesis: Doctoral ThesisDoctor of Philosophy


    MicroRNAs are short endogenous non-coding RNAs that play pivotal roles in a diverse range of cellular processes. The miR-181 family is important in T cell development, proliferation and activation. In this study, we identified BRK1 as a novel target of miR-181c using a dual selection functional assay. Given the importance of miR-181 in T cell functions and the potential role of BRK1 in the WAVE2 complex as well as actin polymerisation in T cells, we therefore investigated the influence of the miR-181c-BRK1 axis in T cell functions. Stimulation of PBMC derived CD3+ T cells resulted in reduced expression of miR- 181c and upregulation of BRK1 protein expression, suggesting that the miR-181c- BRK1 axis might be important in T cell activation. To further assess the role of miR- 181c-BRK1 axis in T cell activation, we overexpressed miR-181c in Jurkat T cells and suppressed BRK1 in Jurkat and primary T cells. We showed that overexpression of miR-181c or suppression of BRK1 resulted in reduction in T cell activation and actin polymerisation coupled with impairment in lamellipodia generation and immunological synapse formation. Additionally, we found that BRK1 silencing led to reduced expressions of other proteins in the WAVE2 complex including WAVE2, ABI1 and SRA1, suggesting that impairment of actin polymerisation-dependent T cell functions were a result of the instability of the WAVE2 complex following BRK1 depletion. We also demonstrated a reciprocal relationship of miR-181c and BRK1 in BM derived CD3+ T cells from MDS patients associated with T-LGL leukaemia, suggesting the regulation of BRK1 protein expression by miR-181c in this group of MDS patients. Collectively, we demonstrated that BRK1 is a novel downstream target of miR-181c and highlighted the important role of miR-181c- BRK1 axis in T cell activation and actin polymerisation-mediated T cell functions.
    Date of Award2017
    Original languageEnglish
    Awarding Institution
    • King's College London
    SupervisorGhulam Mufti (Supervisor) & Joop Gaken (Supervisor)

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