Nuclear phosphatidylinositol 3,4,5-trisphosphate interactome uncovers an enrichment in nucleolar proteins

Abstract

AbstractPolyphosphoinositides (PPIn) play essential functions as lipid signalling molecules and many of their functions have been elucidated in the cytoplasm. However, PPIn are also intranuclear where they contribute to chromatin remodelling, transcription and mRNA splicing. The PPIn, phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P3) has been mapped to the nucleus and nucleoli but its role remains unclear in this subcellular compartment. To gain further insights into the nuclear functions of PtdIns(3,4,5)P3, we applied a previously developed quantitative mass spectrometry-based approach to identify the targets of PtdIns(3,4,5)P3from isolated nuclei. We identified 179 potential PtdIns(3,4,5)P3-interacting proteins and gene ontology analysis for the biological functions of this dataset revealed an enrichment in RNA processing/splicing, cytokinesis, protein folding and DNA repair. Interestingly, about half of these interactors were common to nucleolar protein datasets, some of which had dual functions in rRNA transcription and DNA repair, including Poly(ADP-Ribose) Polymerase 1 (PARP1/ARTD1). PARP1 was found to interact directly with PtdIns(3,4,5)P3as well as PtdIns(3,4)P2and to co-localise with PtdIns(3,4,5)P3in the nucleolus and with PtdIns(3,4)P2in nucleoplasmic foci. In conclusion, the PtdIns(3,4,5)P3interactome reported here identified several nucleolar proteins and further pointed to roles for this lipid in these processes.