CK2 signaling from TOLLIP-dependent perinuclear endosomes is an essential feature of KRAS mutant cancers

Abstract

AbstractOncogenic RAS induces perinuclear translocation of the oncogenic kinases ERK1/2 and CK2 and the MAPK scaffold KSR1, forming endosomal signaling hubs termed perinuclear signaling centers (PSCs). PSCs are found in nearly all cancer cell lines and tumor tissues, suggesting that compartmentalization of oncogenic kinases drives tumorigenesis. We show here that the endosomal adaptor, TOLLIP, tethers RAB11A+ signaling endosomes containing CK2 and KSR1, but not ERK, to the perinuclear ER. TOLLIP binds to the KSR1 CA5 pseudo-kinase domain through a conserved region predicted to form a β-hairpin, thus anchoring PSCs to perinuclear endosomes. TOLLIP is perinuclear in cancer cells and KRasG12D-driven mouse tumors but is pan-cytoplasmic in non-transformed cells, correlating with the presence of PSCs. TOLLIP is required for proliferation/survival of KRAS mutant tumor cells but not HRAS, NRAS and BRAF cancers or non-transformed cells. KRasG12D-induced lung lesions in TollipKO/KOmice showed reduced numbers of carcinomatous lesions, implicating TOLLIP in progression to malignant cancer. Phosphoproteomics studies revealed that perinuclear CK2 phosphorylates specific substrates, particularly proteins involved in ribosome biogenesis and translation such as RIOK1 and eIF4B. In summary, our findings identify TOLLIP as a key signaling adaptor in KRAS tumors whose inhibition is a potential vulnerability of these cancers.