218 - Tyrosine nitration regulates signaling pathways involved in Neurofibromatosis type 2-associated Schwannoma growth

Abstract

Neurofibromatosis type 2 (NF2) is a genetic disorder of the nervous system caused by inactivation of the merlin tumor suppressor gene. NF2 patients develop bilateral vestibular schwannomas (VS) and other nervous system tumors throughout their life for which there is no effective drug treatment. Production of the oxidant peroxynitrite occurs in pathological conditions and leads to tyrosine (Tyr) nitration of proteins. Although Tyr nitration is found in multiple tumor types, its role in tumorigenesis is unknown. We discovered that VS and human merlin-deficient (MD) Schwann cells show significantly increased levels of peroxynitrite and Tyr nitration compared to normal Schwann cells. Notably, prevention of tyrosine nitration selectively decreases MD-Schwann cell survival. Our goal is to identify nitrated proteins that support VS growth as new potential tumor-specific therapeutic targets, enabling the development of safe pharmacological strategies for NF2 schwannomas. This is the first focused effort to determine the signaling pathways regulated by tyrosine nitration in pathological conditions. By performing immunoprecipitations using a polyclonal anti-nitrotyrosine antibody followed by mass spectrometry analysis and western blot, we identified a limited number of proteins endogenously nitrated in VS from NF2 patients, and in mouse and human MD-Schwann cells. A group of the identified proteins play a role in pathways that are dysregulated in NF2. Further, using complementary phospho-kinase arrays, we found that prevention of tyrosine nitration using urate and edaravone has an impact on several of these key signaling pathways. The identification of the specific nitrated proteins that promote schwannoma growth could provide exceptional novel targets for the treatment of NF2 and possibly other tumors of the nervous system as well. Supported by DoD, NRP, NIA W81XWH-17-1-0409 (to MCF).