Absence of Neurofibromin Induces an Oncogenic Metabolic Switch via Mitochondrial ERK-Mediated Phosphorylation of the Chaperone TRAP1

Abstract

Mutations in neurofibromin, a Ras GTPase-activating protein, lead to the tumor predisposition syndrome neurofibromatosis type 1. Here, we report that cells lacking neurofibromin exhibit enhanced glycolysis and decreased respiration in a Ras/ERK-dependent way. In the mitochondrial matrix of neurofibromin-deficient cells, a fraction of active ERK1/2 associates with succinate dehydrogenase (SDH) and TRAP1, a chaperone that promotes the accumulation of the oncometabolite succinate by inhibiting SDH. ERK1/2 enhances both formation of this multimeric complex and SDH inhibition. ERK1/2 kinase activity is favored by the interaction with TRAP1, and TRAP1 is, in turn, phosphorylated in an ERK1/2-dependent way. TRAP1 silencing or mutagenesis at the serine residues targeted by ERK1/2 abrogates tumorigenicity, a phenotype that is reverted by addition of a cell-permeable succinate analog. Our findings reveal that Ras/ERK signaling controls the metabolic changes orchestrated by TRAP1 that have a key role in tumor growth and are a promising target for anti-neoplastic strategies.

Keywords: Ras/ERK signaling; TRAP1; bioenergetics; chaperones; mitochondria; neurofibromin; succinate dehydrogenase; tumor metabolism.