PO-171 Identifying IFITM1-dependent synthetized proteins in interferon gamma stimulated cells

Introduction Interferon-induced transmembrane protein 1 (IFITM1) plays a dual role in restriction of RNA viruses and in metastatic cancer cell growth. IFITM1 expression has been extensively reported in many types of cancer and its high overexpression greatly correlates with tumour progression and leads to a poor outcome. Interferons increase in response to a broad range of factors such as persistent viral infection or DNA damaging agents which activate the JAK kinase-STAT pathway. Ultimately, this signalling cascade will regulate the transcriptional synthesis of over 2000 interferon-stimulated genes (ISG). By contrast, the interferon resistance DNA-damage signature genes (IRDS), which is comprised of a subset of ISG, promote phenotypes that contribute to the tumour development such as resistance to DNA damage, metastasis, and EMT. IFITM1 is a pro-oncogenic receptor which is a component of the IRDS pathway. Material and methods Affinity purification of isotopically labelled cells were analysed by mass spectrometry (MS). Isogenic cell panels were generated using CRISPR gRNAs. Validation of the protein-protein interactions were performed using PLA. Localization of IFITM1 to ribosomal protein and analysis of protein synthesis were analysed MS. Results and discussions How IFITM1 regulates oncogenic cell signalling or viral restriction is not mechanistically defined. A cytosolic association between IFITM1 and SRSF family of splicing factors was identified as possible dominant protein-interaction in interferon treated cells. SRSF1 isoform detected is associated to be in the cytoplasm. As such, we focused on understanding whether IFITM1 is required for protein synthesis in response to interferon signalling. Our results are consistent with previous literature where STAT1 protein is mediated by interferon-dependent stimulus. We also detected new protein synthesis of IRF-1 and IN35 in IFITM1 independent mechanism. Strikingly, we specifically identified a small subset of IFITM1-dependent synthetized proteins upon interferon treatment. These signalling events that will be further investigated are important for anti-viral pathways as well as immune-cancer synapse. Conclusion 1. The results suggested that IFITM1 modulates the ribosomal translation affecting the expression of certain target proteins. 2. We detected some stablished proteins present in the IFN-pathway: STAT-1, IRF-1 and IN35. 3. Further analysis identified a regulatory effect on some target proteins modulated by IFITM1 as well as IFN-stimulation.