Structure of the immunoregulatory sialidase NEU1

Abstract

Sialic acids linked to glycoproteins and glycolipids are important mediators of cell and protein recognition events. These sugar residues are removed by neuraminidases (sialidases). Neuraminidase-1 (sialidase-1 or NEU1) is a ubiquitously expressed mammalian sialidase located in lysosomes and on the cell membrane. Because of its modulation of multiple signaling processes, it is a potential therapeutic target for cancers and immune disorders. Genetic defects in NEU1 or in its protective protein cathepsin A (PPCA, CTSA) cause the lysosomal storage diseases sialidosis and galactosialidosis. To further our understanding of this enzyme’s function at the molecular level, we determined the three-dimensional structure of murine NEU1. The enzyme oligomerizes through two self-association interfaces and displays a wide substrate-binding cavity. A catalytic loop adopts an inactive conformation. We propose a mechanism of activation involving a conformational change in this loop upon binding to its protective protein. These findings may facilitate the development of selective inhibitor and agonist therapies.

Differential transcriptome response following infection of porcine ileal enteroids with species A and C rotaviruses

“…In addition, G9P[13] and RVC infection significantly upregulated the expression of genes encoding proteins associated with SA catabolism with the most prominent change in expression of the gene encoding RENBP enzyme known for its catabolic role in SA metabolism [ 51 ]. Similar effect of these viruses was observed for the expression of gene encoding NEU1—sialidase which removes terminal SA from glycans [ 52 ]. In addition, G9P[13] infection was associated with downregulation of another catalytic enzyme—NPL.…”

Secondary deficiency of neuraminidase 1 contributes to CNS pathology in neurological mucopolysaccharidoses via hypersialylation of brain glycoproteins

“…Human NEU1, GLB1 and CTSA were expressed as secreted proteins in Sf9 insect cells, infected with recombinant baculovirus, and purified as previously described [33,34], except that a TEV protease cleavage site was included between the hexahistidine tag and the catalytic domains of NEU1 and CTSA proteins. NEU1 enzymatic activity assays were carried out in 50 mM sodium acetate buffer, pH 4.5, with 100 mM NaCl and 1 mM of the fluorogenic substrate 4-methylumbelliferyl N-acetyl-α-D-neuraminic acid (4MU-NANA, BioSynth EM05195).…”

“…Coordinates for NEU1 were from the PDB (8DU5) [33]. Initial coordinates for HS tetramers were generated from previous reports [35].…”

“…We further tested if HS would interfere with the activity of the recombinant purified NEU1 or NEU1-CTSA complex in vitro. The proteins were produced in the Sf9 insect cells and purified as previously described [33,34]. Both hexahistidine-tagged and untagged CTSA and NEU1 proteins were tested to exclude the possibility of an unspecific interaction between HS and the positively charged tag.…”