Abstract
The NF1 gene product, neurofibromin, was identified in 1990, yet fundamental questions
remain unanswered concerning its intracellular location(s), binding partners, and signaling
properties. It is known that the large (>200kd) tumor suppressor protein contains a small
domain that turns of RAS proteins, so that loss of NF1 function leads to RAS activation on
cell stimulation. The remaining NF1 sequence can interact with a chaperone, SPRED1, and
other proteins in vitro and/or in specific cell types. In Schwan cells, NF1 loss results in
formation of neurofibromas, tumors in the peripheral nerves. It is still unknown which
interaction partners and RAS proteins are relevant in Schwann cells. Here we propose to
identify NF1 interaction partners, including relevant RAS proteins, that contribute to Schwann
cell tumorigenesis. This is because in mammals there are six highly homologous NF1-related
RAS paralogs, divided into two families. Our studies rely on interdisciplinary approaches,
including cell/mouse genetics, and state of the art biochemical and molecular biology
techniques, and our expertise in preclinical testing. Our preliminary data, enabled by new
reagents and technologies, supports key roles for canonical RAS proteins in NF1 mutant
Schwann cell proliferation. We will now assess the specific roles of RAS proteins in primary
Schwann cells in vitro, and in neurofibroma in vivo, and test a potential targeted therapy in
vivo. Importantly, whether neurofibromin has Schwann cell-specific interaction partners
beyond RAS proteins is unknown. Using proximity biotinylation our preliminary studies
identify novel potential NF1-interaction partners in Schwann cells. We will identify complexes
containing neurofibromin and these proteins and specific RAS paralogs, and additional
complexes that may form on cell stimulation, and test if blocking identified pathways is useful
therapeutically.