AMBRA1 control immune-specific gene expression in T lymphocytes

Autoimmune lymphoproliferative syndrome (ALPS) is a disease characterized by the dysregulation of cell death in lymphocytes, resulting in symptoms such as hepatomegaly, splenomegaly, and anemia. While most patients with ALPS have a mutation in the FAS gene or within the FAS pathway, which helps mediate cell death, some patients who present with ALPS-like symptoms do not have known causative gene mutations. To identify other genes that confer resistance to cell death, and thus may play a role in diseases such as ALPS, we performed a whole genome CRISPR screen of Fas-mediated cell death and identified AMBRA1, a protein previously studied in autophagy and E3 ubiquitin ligase activity. We verified the screen results and indeed found that AMBRA1 KO cells resist Fas-mediated cell death. To identify the mechanism of how AMBRA1 contributes to cell death resistance, we performed cycloheximide chase assays, qPCR, and proteomic analysis and confirmed that AMBRA1 regulates FAS expression. Furthermore, we found that AMBRA1 itself can be upregulated by TCR stimulation through the CD28-PI3K-mTORC1 pathway. Mass spectrometry analysis and subsequent experiments also confirmed that AMBRA1 regulates other immune genes. Together, these data establish a novel function for AMBRA1 as a critical regulator in T cells and unveil new insights into how AMBRA1 may contribute to ALPS and dysregulated cell death in other immune diseases. This research was supported by the Intramural Research Program of the NIH.