title: A Chemical Biology Solution to Problems with Studying Biologically Important but Unstable 9-O-Acetyl Sialic Acids.
abstract: 9-O-Acetylation is a common natural modification on sialic acids (Sias) that terminate many vertebrate glycan chains. This ester group has striking effects on many biological phenomena, including microbe-host interactions, complement action, regulation of immune responses, sialidase action, cellular apoptosis, and tumor immunology. Despite such findings, 9-O-acetyl sialoglycoconjugates have remained largely understudied, primarily because of marked lability of the 9-O-acetyl group to even small pH variations and/or the action of mammalian or microbial esterases. Our current studies involving 9-O-acetylated sialoglycans on glycan microarrays revealed that even the most careful precautions cannot ensure complete stability of the 9-O-acetyl group. We now demonstrate a simple chemical biology solution to many of these problems by substituting the oxygen atom in the ester with a nitrogen atom, resulting in sialic acids with a chemically and biologically stable 9-N-acetyl group. We present an efficient one-pot multienzyme method to synthesize a sialoglycan containing 9-acetamido-9-deoxy-N-acetylneuraminic acid (Neu5Ac9NAc) and compare it to the one with naturally occurring 9-O-acetyl-N-acetylneuraminic acid (Neu5,9Ac2). Conformational resemblance of the two molecules was confirmed by computational molecular dynamics simulations. Microarray studies showed that the Neu5Ac9NAc-sialoglycan is a ligand for viruses naturally recognizing Neu5,9Ac2, with a similar affinity but with much improved stability in handling and study. Feeding of Neu5Ac9NAc or Neu5,9Ac2to mammalian cells resulted in comparable incorporation and surface expression as well as binding to 9-O-acetyl-Sia-specific viruses. However, cells fed with Neu5Ac9NAc remained resistant to viral esterases and showed a slower turnover. This simple approach opens numerous research opportunities that have heretofore proved intractable.
authors.affiliation: Glycobiology Research and Training Center, University of California , San Diego, California 92093, United States.
authors.forename: Zahra
authors.initials: Z
authors.lastname: Khedri
authors.affiliation: Department of Chemistry, University of California , Davis, California 95616, United States.
authors.forename: An
authors.initials: A
authors.lastname: Xiao
authors.affiliation: Department of Chemistry, University of California , Davis, California 95616, United States.
authors.forename: Hai
authors.initials: H
authors.lastname: Yu
authors.affiliation: Glycobiology Research and Training Center, University of California , San Diego, California 92093, United States.
authors.forename: Corinna Susanne
authors.initials: CS
authors.lastname: Landig
authors.affiliation: Department of Chemistry, University of California , Davis, California 95616, United States.
authors.forename: Wanqing
authors.initials: W
authors.lastname: Li
authors.affiliation: Glycobiology Research and Training Center, University of California , San Diego, California 92093, United States.
authors.forename: Sandra
authors.initials: S
authors.lastname: Diaz
authors.affiliation: Department of Microbiology and Immunology, Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University , Ithaca, New York 14853, United States.
authors.forename: Brian R
authors.initials: BR
authors.lastname: Wasik
authors.affiliation: Department of Microbiology and Immunology, Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University , Ithaca, New York 14853, United States.
authors.forename: Colin R
authors.initials: CR
authors.lastname: Parrish
authors.affiliation: Department of Chemistry, University of California , Davis, California 95616, United States.
authors.forename: Lee-Ping
authors.identifier: 0000-0003-3072-9946
authors.initials: LP
authors.lastname: Wang
authors.affiliation: Glycobiology Research and Training Center, University of California , San Diego, California 92093, United States.
authors.forename: Ajit
authors.initials: A
authors.lastname: Varki
authors.affiliation: Department of Chemistry, University of California , Davis, California 95616, United States.
authors.forename: Xi
authors.identifier: 0000-0002-3160-614X
authors.initials: X
authors.lastname: Chen
mesh_terms: D000107:Acetylation; D015703:Antigens, CD / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D006031:Glycosylation; D006389:Hemagglutinins, Viral / Q000378:metabolism; D006801:Humans; D008024:Ligands; D046228:Microarray Analysis; D008968:Molecular Conformation; D056004:Molecular Dynamics Simulation; D009841:Oligonucleotides / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism; D051918:Sialic Acid Binding Ig-like Lectin 2 / Q000378:metabolism; D063265:Sialic Acid Binding Immunoglobulin-like Lectins / Q000378:metabolism; D012794:Sialic Acids / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism*; D017003:Torovirus / Q000201:enzymology; D014760:Viral Fusion Proteins / Q000378:metabolism; D014764:Viral Proteins / Q000378:metabolism
chemical_list: D015703:Antigens, CD; C497867:CD22 protein, human; D006389:Hemagglutinins, Viral; D008024:Ligands; D009841:Oligonucleotides; C412227:SIGLEC9 protein, human; D051918:Sialic Acid Binding Ig-like Lectin 2; D063265:Sialic Acid Binding Immunoglobulin-like Lectins; D012794:Sialic Acids; D014760:Viral Fusion Proteins; D014764:Viral Proteins; C060814:hemagglutinin esterase