title: Sialidase NEU3 dynamically associates to different membrane domains specifically modifying their ganglioside pattern and triggering Akt phosphorylation.
abstract: Lipid rafts are known to regulate several membrane functions such as signaling, trafficking and cellular adhesion. The local enrichment in sphingolipids and cholesterol together with the low protein content allows their separation by density gradient flotation after extraction with non-ionic detergent at low temperature. These structures are also referred to as detergent resistant membranes (DRM). Among sphingolipids, gangliosides play important roles in different biological events, including signal transduction and tumorigenesis. Sialidase NEU3 shows high enzymatic specificity toward gangliosides. Moreover, the enzyme is present both at the cell surface and in endosomal structures and cofractionates with caveolin. Although changes in the expression level of NEU3 have been correlated to different tumors, little is known about the precise distribution of the protein and its ability in modifying the ganglioside composition of DRM and non-DRM, thus regulating intracellular events. By means of inducible expression cell system we found that i) newly synthesized NEU3 is initially associated to non-DRM; ii) at steady state the protein is equally distributed between the two membrane subcompartments, i.e., DRM and non-DRM; iii) NEU3 is degraded via the proteasomal pathway; iv) the enzyme specifically modifies the ganglioside composition of the membrane areas where it resides; and v) NEU3 triggers phosphorylation of Akt, even in absence of exogenously administered EGF. Taken together our data demonstrate that NEU3 regulates the DRM ganglioside content and it can be considered as a modulator of Akt phosphorylation, further supporting the role of this enzyme in cancer and tumorigenesis.
authors.affiliation: Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy.
authors.forename: Dario
authors.initials: D
authors.lastname: Bonardi
authors.affiliation: Department of Medical Biotechnology and Translational Medicine, University of Milan, Milan, Italy.
authors.forename: Nadia
authors.initials: N
authors.lastname: Papini
authors.affiliation: Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy.
authors.forename: Mario
authors.initials: M
authors.lastname: Pasini
authors.affiliation: Department of Medical Biotechnology and Translational Medicine, University of Milan, Milan, Italy.
authors.forename: Loredana
authors.initials: L
authors.lastname: Dileo
authors.affiliation: Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy.
authors.forename: Flavia
authors.initials: F
authors.lastname: Orizio
authors.affiliation: Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy.
authors.forename: Eugenio
authors.initials: E
authors.lastname: Monti
authors.affiliation: Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy.
authors.forename: Luigi
authors.initials: L
authors.lastname: Caimi
authors.affiliation: Department of Medical Biotechnology and Translational Medicine, University of Milan, Milan, Italy.
authors.forename: Bruno
authors.initials: B
authors.lastname: Venerando
authors.affiliation: Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Bresciani
mesh_terms: D000818:Animals; D003902:Detergents / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005732:Gangliosides / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007976:Leupeptins / Q000494:pharmacology; D021962:Membrane Microdomains / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D009439:Neuraminidase / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D059748:Proteolysis / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*
chemical_list: D003902:Detergents; D005732:Gangliosides; D007976:Leupeptins; D049452:Green Fluorescent Proteins; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; C511796:Neu3 protein, mouse; D009439:Neuraminidase; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde