Overexpression of ezrin inactivates NF2 tumor suppressor in glioblastoma
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Defining Gene Functions in Tumorigenesis by Ex vivo Ablation of Floxed Alleles in Malignant Peripheral Nerve Sheath Tumor Cells
Published on: August 25, 2021
Fabiana C Morales1, Jennifer R Molina, Yuho Hayashi
1Department of Neuro-Oncology, The University of Texas M. D. Anderson Cancer Center, 6767 Bertner Avenue, Houston, TX 77030, USA.
Abstract:
Glioblastoma is a frequent brain malignancy with a dismal prognosis. The molecular changes causing its aggressive phenotype are under investigation. We report that the cytoskeletal-related proteins neurofibromatosis type 2 (NF2) and ezrin have opposite yet interdependent activities in glioblastoma growth. We show that NF2 is absent in approximately one-third of glioblastoma cell lines and tumors, and that it suppresses growth when expressed in cells. Although ezrin overexpression was previously observed in glioblastoma, we show here that ezrin enhanced cell proliferation and anchorage-independent growth but only in cells expressing NF2. Ezrin interacted and delocalized NF2 from the cortical compartment releasing its inhibition on Rac1. By using swap NF2-ezrin molecules, we identified that the opposite effects on cell growth of NF2 and ezrin depend on their amino-terminal FERM domain. The subcellular cortical localization appeared important for NF2 suppressive activity. In contrast, the ability of ezrin to enhance growth or complex NF2 did not depend on the molecular conformation or subcellular localization. In conclusion, these studies show 2 mechanisms for NF2 inactivation in glioblastoma: (i) decreased protein expression and (ii) increasing dosages of ezrin that disable NF2 by intermolecular association and aberrant intracellular recruitment.
Insights
Neurofibromatosis type 2 (NF2) and ezrin proteins have opposing roles in glioblastoma growth. NF2 loss or ezrin overexpression inactivates NF2, promoting aggressive tumor growth.
Area of Science:
- Oncology
- Molecular Biology
- Cell Biology
Background:
- Glioblastoma is an aggressive brain cancer with poor outcomes.
- Molecular mechanisms driving glioblastoma's aggressive nature are under investigation.
- Cytoskeletal proteins neurofibromatosis type 2 (NF2) and ezrin exhibit complex interactions.
Purpose of the Study:
- To investigate the interdependent roles of NF2 and ezrin in glioblastoma.
- To elucidate the mechanisms by which NF2 and ezrin influence glioblastoma cell proliferation and growth.
- To identify how NF2 inactivation occurs in glioblastoma.
Main Methods:
- Analysis of NF2 and ezrin expression in glioblastoma cell lines and tumors.
- Functional studies using cell proliferation and anchorage-independent growth assays.
- Investigation of protein interactions and subcellular localization using molecular techniques.
- Experimental manipulation using swap NF2-ezrin molecules and analysis of the FERM domain.
Main Results:
- NF2 is absent in about one-third of glioblastomas and suppresses growth when expressed.
- Ezrin enhances glioblastoma cell proliferation and anchorage-independent growth, but only in NF2-expressing cells.
- Ezrin interacts with NF2, causing its delocalization from the cell cortex and releasing inhibition on Rac1.
- The N-terminal FERM domain dictates the opposing effects of NF2 and ezrin on cell growth.
Conclusions:
- Glioblastoma can inactivate NF2 through decreased protein expression or increased ezrin levels.
- Ezrin disables NF2 via intermolecular association and aberrant intracellular recruitment, promoting tumor growth.
- Understanding these mechanisms offers potential therapeutic targets for glioblastoma.
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