Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.1.53 (sialidase)
 2,694 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Four-transmembrane-domain proteins of the tetraspanin superfamily are the organizers of specific microdomains at the membrane [TERMs (tetraspanin-enriched microdomains)] that incorporate various transmembrane receptors and modulate their activities. The structural aspects of the organization of TERM are poorly understood. In the present study, we investigated the role of gangliosides in the assembly and stability of TERM. We demonstrated that inhibition of the glycosphingolipid biosynthetic pathway with specific inhibitors of glucosylceramide synthase [NB-DGJ (N-butyldeoxygalactonojirimycin) and PPMP (D-threo-1-phenyl-2-hexadecanoylamino-3-morpholino-1-propanol.HCl)] resulted in specific weakening of the interactions involving tetraspanin CD82. Furthermore, ectopic expression of the plasma-membrane-bound sialidase Neu3 in mammary epithelial cells also affected stability of the complexes containing CD82: its association with tetraspanin CD151 was decreased, but the association with EGFR [EGF (epidermal growth factor) receptor] was enhanced. The destabilization of the CD82-containing complexes upon ganglioside depletion correlated with the re-distribution of the proteins within plasma membrane. Importantly, depletion of gangliosides affected EGF-induced signalling only in the presence of CD82. Taken together, our results provide strong evidence that gangliosides play an important role in supporting the integrity of CD82-enriched microdomains. Furthermore, these results demonstrate that the association between different tetraspanins in TERM is controlled by distinct mechanisms and identify Neu3 as a first physiological regulator of the integrity of these microdomains.
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PMID:Gangliosides play an important role in the organization of CD82-enriched microdomains. 1685 90

Mammalian sialidases are key enzymes in the degradation of glycoconjugates. Neu4L sialidase is localized to mitochondria and specifically expressed in brain. To elucidate the pathophysiological roles of Neu4L in the nervous system, we investigated the possible involvement of Neu4L in the apoptotic neurodegeneration under the existence of catechol metabolites generated by tyrosinase. We demonstrated that: (i) the expression level of Neu4L was dramatically decreased prior to apoptosis; (ii) the apoptotic phenotype was characterized by cytochrome c release into cytosol concomitant with the trafficking of ganglioside GD3 to mitochondria; and (iii) the inhibitor of glucosylceramide synthase partially recovered cell viability. Neu4L and its substrate GD3 may act as key molecules in the mitochondrial apoptotic pathway in neuronal cells.
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PMID:Role of Neu4L sialidase and its substrate ganglioside GD3 in neuronal apoptosis induced by catechol metabolites. 1723 88

The membrane type sialidase (Neu3) has been suggested to participate in cell growth, migration and differentiation. To determine whether a Neu3 is able to modulate megakaryocytic differentiation of K562 cells, we studied the functional significance of human Neu3 induced by phorbol 12-myristate 13-acetate (PMA). Northern blot and reverse transcription-polymerase chain reaction (RT-PCR) indicated that the induction of hST3Gal V, which synthesizes ganglioside GM3 and reduction of Neu3 by PMA, are linked for the expression of differentiation marker protein, CD41b surface antigen. To elucidate the mechanism underlying the down-regulation of the CD41b surface antigen expression when Neu3 gene is expressed in PMA-treated cells, we characterized the Neu3-mediated signaling pathway. Neu3 overexpression inhibited the PMA-induced ERK1/2 and p38 MAPK phosphorylation in the K562 cells. Down-regulation of expression of CD41b surface antigen was dependent on expression of Neu3 gene. However, a Neu3 inhibitor Neu5Ac2en induced morphological changes, showing megakaryocytic differentiation of K562 cells, with expression of CD41b surface antigen, while a specific glucosylceramide synthase inhibitor PDMP inhibited megakaryocytic differentiation of K562 cells. The molecular mechanisms involved in Neu3-involved inhibition of CD41b surface antigen expression in K562 cells have been suggested: the Neu3 degrades membrane sialic acids and the resulting signaling pathway of the PKC/ERKs/p38 MAPK is down-regulated, causing a decrease in CD41b surface antigen expression and inhibition of megakaryocytic differentiation of K562 cells.
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PMID:Membrane type sialidase inhibits the megakaryocytic differentiation of human leukemia K562 cells. 1833 27