Membrane sialidase NEU3 is highly expressed in human melanoma cells promoting cell growth with minimal changes in the composition of gangliosides.

Department of Biomedical Sciences, Chubu University College of Life and Health Sciences, Aichi, Japan.
Cancer Science (Impact Factor: 3.53). 09/2011; 102(12):2139-49. DOI: 10.1111/j.1349-7006.2011.02086.x
Source: PubMed

ABSTRACT NEU3 is a membrane sialidase specific for gangliosides. Its increased expression and implication in some cancers have been reported. Here, we analyzed NEU3 expression in malignant melanoma cell lines and its roles in the cancer phenotypes. Quantitative RT-PCR revealed that high levels of the NEU3 gene were expressed at almost equivalent levels with those in colon cancers. To examine the effects of overexpression of NEU3, NEU3 cDNA-transfectant cells were established using a melanoma cell line SK-MEL-28 and its mutant N1 lacking GD3. SK-MEL-28 sublines overexpressing both the NEU3 gene and NEU3 enzyme activity showed no changes in both cell growth and ganglioside expression, while N1 cells showed a mild increase in cell proliferation with increased phosphorylation of the EGF receptor and neo-synthesis of Gb3 after NEU3 transfection. In contrast, NEU3 silencing resulted in a definite reduction in cell growth in a melanoma line MeWo, while ganglioside patterns underwent minimal changes. Phosphorylation levels of ERK1/2 with serum stimulation decreased in the NEU3-silenced cells. All these results suggest that NEU3 is highly expressed to enhance malignant phenotypes including apoptosis inhibition in malignant melanomas.

  • [Show abstract] [Hide abstract]
    ABSTRACT: Our studies during the early 1970s showed that expression of GM3, the simplest ganglioside and an abundant animal cell membrane component, is reduced during malignant transformation of cells by oncogenic viruses. Levels of mRNA for GM3 synthase were reduced in avian and mammalian cells transformed by oncoprotein "v-Jun", and overexpression of GM3 synthase in the transformed cells caused reversion from transformed to normal cell-like phenotype. GM3 has a well-documented inhibitory effect on activation of growth factor receptors (GFRs), particularly epidermal GFR (EGFR). De-N-acetyl GM3, which is expressed in some invasive human cancer cells, has an enhancing effect on EGFR activation. The important role of the sialosyl group of GM3 was demonstrated using NEU3, a plasma membrane-associated sialidase that selectively remove sialic acids from gangliosides GM3 and GD1a and is up-regulated in many human cancer cells. GM3 is highly enriched in a type of membrane microdomain termed "glycosynapse", and forms complexes with co-localized cell signaling molecules, including Src family kinases, certain tetraspanins (e.g., CD9, CD81, CD82), integrins, and GFRs (e.g., fibroblast growth factor receptor and hepatocyte growth factor receptor c-Met). Studies by our group and others indicate that GM3 modulates cell adhesion, growth, and motility by altering molecular organization in glycosynaptic microdomains and the activation levels of co-localized signaling molecules that are involved in cancer pathogenesis.
    Glycoconjugate Journal 01/2015; 32(1-2). DOI:10.1007/s10719-014-9572-4 · 1.95 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In addition to alterations concerning the expression of oncogenes and onco-suppressors, melanoma is characterized by the presence of distinctive gangliosides (sialic acid carrying glycosphingolipids). Gangliosides strongly control cell surface dynamics and signaling; therefore, it could be assumed that these alterations are linked to modifications of cell behavior acquired by the tumor. On these bases, this work investigated the correlations between melanoma cell ganglioside metabolism profiles and the biological features of the tumor and the survival of patients.
    BMC Cancer 08/2014; 14(1):560. DOI:10.1186/1471-2407-14-560 · 3.32 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Aims: Mitochondrial Ca<sup>2+</sup> homeostasis is crucial for balancing cell survival and death. The recent discovery of the molecular identity of the mitochondrial Ca<sup>2+</sup> uniporter pore (MCU) opens new possibilities for applying genetic approaches to study mitochondrial Ca<sup>2+</sup> regulation in various cell types including cardiac myocytes. Basal tyrosine phosphorylation of MCU was reported from mass spectroscopy of human and mouse tissues, but the signaling pathways that regulate mitochondrial Ca<sup>2+</sup> entry through post-translational modifications of MCU are completely unknown. Therefore, we investigated α<sub>1</sub>-adrenergic-mediated signal transduction of MCU post-translational modification and function in cardiac cells. Results: α<sub>1</sub>-adrenoceptor (α<sub>1</sub>-AR) signaling translocated activated proline-rich tyrosine kinase 2 (Pyk2) from cytosol to mitochondrial matrix and accelerates mitochondrial Ca<sup>2+</sup> uptake via Pyk2-dependent MCU phosphorylation and tetrametric MCU channel pore formation. Moreover, we found that α<sub>1</sub>-AR stimulation increases reactive oxygen species (ROS) production at mitochondria, mitochondrial permeability transition pore (mPTP) activity, and initiates apoptotic signaling via Pyk2-dependent MCU activation and mitochondrial Ca<sup>2+</sup> overload. Innovation: Our data indicates that inhibition of α<sub>1</sub>-AR-Pyk2-MCU signaling represents a potential novel therapeutic target to limit or prevent mitochondrial Ca<sup>2+</sup> overload, oxidative stress, mitochondrial injury, and myocardial death during pathophysiological conditions where chronic adrenergic stimulation is present. Conclusion: The α<sub>1</sub>-AR-Pyk2 dependent tyrosine phosphorylation of the MCU regulates mitochondrial Ca<sup>2+</sup> entry and apoptosis in cardiac cells.
    Antioxidants & Redox Signaling 05/2014; DOI:10.1089/ars.2013.5394 · 7.67 Impact Factor