In Silico Identification of New Putative Pathogenic Variants in the Neu1 Sialidase Gene Affecting Enzyme Function and Subcellular Localization

Abstract

The NEU1 gene is the first identified member of the human sialidases, glycohydrolitic enzymes that remove the terminal sialic acid from oligosaccharide chains. Mutations in NEU1 gene are causative of sialidosis (MIM 256550), a severe lysosomal storage disorder showing autosomal recessive mode of inheritance. Sialidosis has been classified into two subtypes: sialidosis type I, a normomorphic, late-onset form, and sialidosis type II, a more severe neonatal or early-onset form. A total of 50 causative mutations are reported in HGMD database, most of which are missense variants. To further characterize the NEU1 gene and identify new functionally relevant protein isoforms, we decided to study its genetic variability in the human population using the data generated by two large sequencing projects: the 1000 Genomes Project (1000G) and the NHLBI GO Exome Sequencing Project (ESP). Together these two datasets comprise a cohort of 7595 sequenced individuals, making it possible to identify rare variants and dissect population specific ones. By integrating this approach with biochemical and cellular studies, we were able to identify new rare missense and frameshift alleles in NEU1 gene. Among the 9 candidate variants tested, only two resulted in significantly lower levels of sialidase activity (p<0.05), namely c.650T>C and c.700G>A. These two mutations give rise to the amino acid substitutions p.V217A and p.D234N, respectively. NEU1 variants including either of these two amino acid changes have 44% and 25% residual sialidase activity when compared to the wild-type enzyme, reduced protein levels and altered subcellular localization. Thus they may represent new, putative pathological mutations resulting in sialidosis type I. The in silico approach used in this study has enabled the identification of previously unknown NEU1 functional alleles that are widespread in the population and could be tested in future functional studies.

Dengue Virus Alters Sialic Acid Residues Configuration in Macrophages

“…LPS binding to TLR-4 is well detailed in the literature the removal of sialic acid for activation downstream, as today there is no evidence for Dengue infection and sialic acids in macrophages, this is the reason LPS was used as a positive control of proinflammatory profile for monocytes/macrophages (Bonardi et al 2014;Amith et al 2010).…”

“…In human macrophages, LPS binding to TLR-2, -3, and -4 induces neuraminidase activity of Neu-1, which hydrolyzes α-2,3 residues in the β-galactoses present in glycoproteins, this later induces the receptor dimerization and downstream signaling activity. (Bonardi et al 2014;Amith et al 2010).…”

Sialylation of host proteins as targetable risk factor for COVID‐19 susceptibility and spreading: A hypothesis

“…In this context, it would be conceivable to: IDENTIFY A RISK FACTOR FOR SARS‐CoV‐2 SUSCEPTIBILITY and SPREAD by evaluating the expression levels of NEU1 mRNA in human samples (the lowest NEU1 levels should correspond to worst prognosis and fit our super spreader hypothesis). by screening the general population for NEU1 synonymous variants known to lower NEU1 enzyme activity 72 as well as pathogenic mutations in carriers. These analyses will ascertain the involvement of NEU1 functional variants in the pathogenesis of COVID‐19. APPLY UNCONVENTIONAL THERAPY TO INCREASE NEU1 LEVELS …”

The role of neuraminidase in TLR4‐MAPK signalling and the release of cytokines by lupus serum‐stimulated mesangial cells

“…The only other NEU detectable in the kidney is NEU3 with message levels of Neu1 expressed approximately 40‐fold higher than Neu3, 19 and NEU1 and NEU3 proteins are readily detected in the glomeruli of renal tissue sections of MRL/lpr lupus mice 12 . While NEU1 was largely observed to desialylate glycoproteins, NEU3 showed a preference for glycolipids (gangliosides) 25‐29 and their activity at the plasma membrane impacts receptor activation and signalling in a variety of cell types 29‐35 …”