Merlin, a “magic” linker between extracellular cues and intracellular signaling pathways that regulate cell motility, proliferation, and survival

Department of Oncological Sciences, Mount Sinai School of Medicine, New York, NY10029, USA.
Current Protein and Peptide Science (Impact Factor: 2.33). 09/2010; 11(6):471-84. DOI: 10.2174/138920310791824011
Source: PubMed

ABSTRACT Genetic alterations of neurofibromatosis type 2 (NF2) gene lead to the development of schwannomas, meningiomas, and ependymomas. Mutations of NF2 gene were also found in thyroid cancer, mesothelioma, and melanoma, suggesting that it functions as a tumor suppressor in a wide spectrum of cells. The product of NF2 gene is merlin (moesin-ezrin-radixin-like protein), a member of the Band 4.1 superfamily proteins. Merlin shares significant sequence homology with the ERM (Ezrin-Radixin-Moesin) family proteins and serves as a linker between transmembrane proteins and the actin-cytoskeleton. Merlin is a multifunctional protein and involved in integrating and regulating the extracellular cues and intracellular signaling pathways that control cell fate, shape, proliferation, survival, and motility. Recent studies showed that merlin regulates the cell-cell and cell-matrix adhesions and functions of the cell surface adhesion/extracellular matrix receptors including CD44 and that merlin and CD44 antagonize each other's function and work upstream of the mammalian Hippo signaling pathway. Furthermore, merlin plays important roles in stabilizing the contact inhibition of proliferation and in regulating activities of several receptor tyrosine kinases. Accumulating data also suggested an emerging role of merlin as a negative regulator of growth and progression of several non-NF2 associated cancer types. Together, these recent advances have improved our basic understanding about merlin function, its regulation, and the major signaling pathways regulated by merlin and provided the foundation for future translation of these findings into the clinic for patients bearing the cancers in which merlin function and/or its downstream signaling pathways are impaired or altered.

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    • "It exists in ten isoforms, with isoform-1 and −2 being the most common. All isoforms possess an N-terminal part, which contains the four point one Erzin-Radixin-Moezin (FERM) domain, followed by an alpha-helical domain, and a hydrophilic tail [18]. Merlin is involved in the control of various aspects of the cell cycle and the tumorigenesis (Fig. 1) [4] [19] [20]. "
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    ABSTRACT: Merlin, a tumor suppressor protein, controls essential steps of cell cycle, and its deficiency results in cellular overgrowth, proliferation, angiogenesis, invasion and metastasis. Lack of Merlin is responsible for neurofibromatosis-2, most schwannomas, and many meningiomas and ependymomas. We hypothesize that there is a role for statins to ameliorate Merlin's deficiency in this set of tumors by inhibiting a number of Merlin's downstream effectors, the small Rho-GTP-ases, and we present the relevant data. The ultimate goal is to offer a medical therapy promising to halt or reduce the tumor growth-rate in patients harboring Merlin-deficient neoplasms and to provide an adjuvant systemic therapy for patients undergoing stereotactic radio-surgery and partial tumor resection.
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    ABSTRACT: There are several well-characterized hereditary syndromes that predispose to the development of tumors of the nervous system, and that result from germline mutations in high-penetrance genes. In this review, we provide a brief overview of these syndromes. The elucidation of the molecular basis of hereditary syndromes has greatly contributed to our understanding of the pathogenesis of human neoplasms. Signaling pathways involved in hereditary syndromes predisposing to the development of nervous system tumors include RAS, WNT, RB1, TP53, and PTCH signaling pathways, which play key roles in gene regulation, apoptosis, and cell proliferation. The discovery of the genetic origin of nervous system tumors in patients with familial cancer syndromes has been the basis for target identification and drug development. This process has resulted in exciting novel and innovative therapeutic approaches. We also briefly review two important advances in this area: the treatment of medulloblastomas in patients with mutations in the PTCH1 gene, and the discovery of deregulated mammalian target of rapamycin as a major oncogenic driver molecule in patients with TSC mutations and subependymal giant cell astrocytoma. Progress in the understanding of hereditary nervous system tumors is increasingly important for diagnosis and treatment.
    Current opinion in neurology 10/2010; 23(6):583-91. DOI:10.1097/WCO.0b013e3283405b5f · 5.73 Impact Factor
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    ABSTRACT: Mammalian mitogen-activated protein kinase (MAPK) signaling pathways respond to diverse extracellular signals and coordinate a range of cellular responses. Mixed lineage kinase 3 (MLK3) is a member of the mixed lineage kinase family of MAPK kinase kinases (MAP3Ks) that functions to regulate multiple MAPK signaling pathways. Activated forms of the Rho GTP ases, Rac and Cdc42, interact with MLK3 through the Cdc42/Rac-interactive binding (CRIB) motif and promote MLK3 catalytic activity. Our recent findings demonstrate that merlin, the product of the neurofibromatosis type 2 (NF2) tumor suppressor gene, is a physiological inhibitor of MLK3. Our results suggest that merlin inhibits MLK3 activity by blocking the Cdc42-MLK3 interaction. In this commentary, the effect of merlin on Cdc42-mediated activation of MLK3 and MAPK signaling will be discussed.
    Small GTPases 11/2010; 1(3):183-186. DOI:10.4161/sgtp.1.3.14935
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