Post-translational regulation of Foxp3 : identification of novel molecular targets for immune modulation

Abstract

Maintenance of immune homeostasis is a complex process allowing the immune system to be both aggressive enough to eradicate cells that express foreign antigens, and yet provide sensitivity to tolerate cells expressing self antigens. Key modulators allowing tolerance of host antigens, thereby preventing autoimmunity are the regulatory T cells (Treg). The transcription factor Foxp3 is of critical importance for both Treg development and function, and thereby the maintenance of immune homeostasis. Although the transcriptional regulation of Foxp3 has been well investigated, mechanisms of post-translational regulation remain poorly understood. Here we sought to investigate the molecular mechanisms regulating Foxp3 protein expression and the potential for modulation of transcriptional activity by co-factor association. We report, several novel findings including: a) regulation of Treg functionality by acetylation-mediated Foxp3 protein stabilization, (b) rapid temporal control of Foxp3 protein degradation by Sirtuin-1, (c) Increased Treg mediated suppression through USP7/HAUSP-mediated Foxp3, (d) inhibition of Treg function through inhibition of Foxp3 by canonical Wnt signaling. A better understanding of the mechanisms by which Foxp3 is regulated could provide novel therapeutic strategies to control inappropriate (auto)immuunresposes