Project description:We have found a broad case of tumour suppressor hypersensitivity for Merlin in cancer: Merlin expression in Merlin deficient cells (but not Merlin wild type cells) strongly suppresses proliferation regardless of tumour type or of additional somatic mutations. To study how Merlin selectively induced growth arrest in Merlin-deficient cells, global gene expression regulation by Merlin was examined by microarray in a set of four cell line pairs derived from different tumour types Four Merlin-deficient and four Merlin wild type cell lines derived from four different tissues/tumour types (meninges, thyroid, kidney, breast) were infected with pLEX lentiviruses (Open Biosystems) expressing either wt Merlin or Merlin L46R (a tumour-derived loss-of-function mutant, used as a control). 24 hours after infection, fresh media containing 2.5ug/ml puromycin was added (drug selection) and cells grown for a further 24 hours, i.e. cells were harvested 48hour after infection. RNA was analyzed using GeneChip Human Gene 2.0 ST arrays (Affymetrix). n=2 for Merlin-deficient cell lines; n=1 for Merlin wt cell lines
Project description:The neurofibromatosis type 2 (NF2) tumor suppressor, Merlin, is a membrane/cytoskeleton-associated protein that mediates contact-dependent inhibition of proliferation. Here we show that upon cell-cell contact Merlin coordinates the processes of adherens junction stabilization and negative regulation of epidermal growth factor receptor (EGFR) signaling by restraining the EGFR into a membrane compartment from which it can neither signal nor be internalized. In confluent Nf2(-/-) cells, EGFR activation persists, driving continued proliferation that is halted by specific EGFR inhibitors. These studies define a new mechanism of tumor suppression, provide mechanistic insight into the poorly understood phenomenon of contact-dependent inhibition of proliferation, and suggest a therapeutic strategy for NF2-mutant tumors.
Project description:The merlin-ERM (ezrin, radixin, moesin) family of proteins plays a central role in linking the cellular membranes to the cortical actin cytoskeleton. Merlin regulates contact inhibition and is an integral part of cell-cell junctions, while ERM proteins, ezrin, radixin and moesin, assist in the formation and maintenance of specialized plasma membrane structures and membrane vesicle structures. These two protein families share a common evolutionary history, having arisen and separated via gene duplication near the origin of metazoa. During approximately 0.5 billion years of evolution, the merlin and ERM family proteins have maintained both sequence and structural conservation to an extraordinary level. Comparing crystal structures of merlin-ERM proteins and their complexes, a picture emerges of the merlin-ERM proteins acting as switchable interaction hubs, assembling protein complexes on cellular membranes and linking them to the actin cytoskeleton. Given the high level of structural conservation between the merlin and ERM family proteins we speculate that they may function together.