title: 9-O-acetylated sialic acids have widespread but selective expression: analysis using a chimeric dual-function probe derived from influenza C hemagglutinin-esterase.
abstract: While 9-O-acetylation of sialic acids has been reported in some mammalian tissues, the distribution of this modification on specific cell types and molecules is largely unknown. The influenza C virus hemagglutinin-esterase is a membrane-bound glycoprotein that binds specifically to 9-O-acetylated sialic acids (hemagglutinin activity) and then hydrolyzes the O-acetyl group (receptor-destroying activity). A recombinant soluble form of influenza C virus hemagglutinin-esterase wherein the C-terminal transmembrane and cytoplasmic domains are replaced by the Fc portion of human IgG retains both its recognition and enzymatic functions. The latter activity can selectively remove 9-O-acetyl groups from bound or free sialic acids and, under specific conditions, 7-O-acetyl groups as well. Irreversible inactivation of the esterase unmasks stable recognition activity, giving a molecule that binds specifically to 9-O-acetylated sialic acids. These probes demonstrate widespread but selective expression of 9-O-acetylated sialic acids in certain cell types of rat tissues. Patterns of polarized or gradient expression further demonstrate the regulated nature of this modification. Direct probing of blots and thin-layer plates shows selective expression of 9-O-acetylation on certain glycoproteins and glycolipids in such tissues. Thus, 9-O-acetylation is more widespread than previously thought and occurs on specific molecules and cell types.
authors.affiliation: Glycobiology Program, Cancer Center, University of California, San Diego, La Jolla 92093.
authors.forename: A
authors.initials: A
authors.lastname: Klein
authors.forename: M
authors.initials: M
authors.lastname: Krishna
authors.forename: N M
authors.initials: NM
authors.lastname: Varki
authors.forename: A
authors.initials: A
authors.lastname: Varki
mesh_terms: D000818:Animals; D004950:Esterases / Q000235:genetics / Q000378:metabolism; D006017:Glycolipids / Q000737:chemistry / Q000302:isolation & purification; D006023:Glycoproteins / Q000737:chemistry / Q000302:isolation & purification; D006389:Hemagglutinins, Viral / Q000235:genetics / Q000378:metabolism; D006651:Histocytochemistry; D009982:Gammainfluenzavirus / Q000201:enzymology / Q000235:genetics; D015335:Molecular Probes; D051381:Rats; D017207:Rats, Sprague-Dawley; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012794:Sialic Acids / Q000302:isolation & purification*; D014018:Tissue Distribution; D014760:Viral Fusion Proteins; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D006017:Glycolipids; D006023:Glycoproteins; D006389:Hemagglutinins, Viral; D015335:Molecular Probes; D011993:Recombinant Fusion Proteins; D012794:Sialic Acids; D014760:Viral Fusion Proteins; D014764:Viral Proteins; C060814:hemagglutinin esterase; C025676:9-O-acetyl-N-acetylneuraminic acid; D004950:Esterases