Merlin-ASPP2 Tumor Suppressor Interactions in Mechanosensory Signal Transduction from Schwann Cell Junctions in Neurofibromatosis Type 2
Abstract
Neurofibromatosis Type 2 is a genetic disorder characterized by schwannomas. Because conventional chemotherapy is not an effective treatment for these slow growing tumors, new therapies must be devised. In order to do this, it is critical to understand the basic biology behind the disease. Neurofibromatosis Type 2 is caused by a mutation in the tumor suppressor gene, NF2, which results in the loss of a protein called Merlin. It is the absence of Merlin that causes the disease. Unfortunately, exactly what Merlin does and how it does it remains unclear. Therefore, in order to develop an effective therapy, it is critical to understand exactly what we do not currently know, namely, what is Merlin’s true function in cells. What is clear is that, in order for Merlin to function, it must interact with many different proteins in cells, but there is no consensus as to which of these protein interactions is critical to preventing the disease. We do know that, unlike normal Schwann cells, schwannoma cells do not stop growing when they come in close contact with one another. This abnormality, called loss of contact inhibition, is thought to be critical in the development of many kinds of tumors and is regulated by cell junctions, complex structures at the periphery of cells that sense interactions between cells or between cells and their outside environment; they are complex structures that connect mechanical forces with cell signaling. We set out to ask: What are the proteins that Merlin interacts with to prevent schwannoma formation? What does Merlin do to these proteins when it binds them and what happens to these proteins when Merlin is gone that causes tumors to form? To answer these questions, we have successfully adopted a new method, proximity biotinylation, and shown that it is a powerful new way to investigate Merlin function. Proximity biotinylation allows us to identify at least 52 proteins that Merlin interacts with in a living Schwann cell. The majority of these proteins are known components of cell junctions. As powerful as it is, proximity biotinylation experiments do not distinguish proteins that touch Merlin directly versus those that those that are merely close to Merlin. To overcome this limitation, we developed a new method to rapidly test whether a protein binds to Merlin. After several years of intense effort, we have optimized use of these technologies in Schwann cells. We identified a new direct Merlin-binding protein, ASPP2, which is known to play a key role in cancer. In this application, we take advantage of our expertise with this new technology. Our objectives are to determine whether the Merlin-ASPP2 interaction is necessary for Merlin function. This will test whether ASPP2 binds to Merlin to transfer a growth-inhibiting signal from junctions that is lost in schwannoma cells (Aim 1). We will also identify the proteins that connect Merlin and ASPP2 complexes with cell junctions (Aim 2a) and identify additional Merlin direct interactors from our 52 genes in our proximity biotinylation map (Aim 2b.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 10, 2021
- Source ID
- W81XWH2010377
Entities
People
- Robert F Hennigan
Organizations
- United States Army