Disease relevance of St6gal1

• This was accomplished by using a novel baculovirus vector designed to express a mammalian alpha2,6-sialyltransferase early in infection and a new insect cell line stably transformed to constitutively express a mammalian beta1,4-galactosyltransferase [1].
• A polyclonal antibody, a bacteriophage-derived endo-neuraminidase, and an Escherichia coli K1 sialyltransferase are all specific for either recognizing or synthesizing poly(sialic acid) containing alpha-2,8-ketosidic linkages [2].
• Sialyltransferase of the 13762 rat mammary ascites tumor cells [3].
• In this study the regulation of sialyltransferase expression by dexamethasone in H35 rat hepatoma cells is assessed by Northern hybridization and enzyme activity assays [4].
• Slices were prepared from control rats and rats suffering from the acute-phase response, where release of sialyltransferase is increased substantially [Lammers & Jamieson (1988) Biochem. J. 256, 623-631; Kaplan, Woloski, Hellman & Jamieson (1983) J. Biol. Chem. 258, 11505-11509] [5].

High impact information on St6gal1

• Sialyltransferase and sialic acid residues were not detected in medial and cis-cisternae of the Golgi apparatus [6].
• Sialyltransferase (Gal beta 1,4GlcNAc alpha 2,6 sialyltransferase) was localized by immunoelectron microscopy in rat liver hepatocytes using affinity-purified antibodies [6].
• Immunoreactivity for sialyltransferase was found in the Golgi apparatus, where it was restricted to an interconnected system consisting of the trans-cisternae and the trans-tubular network [6].
• Microsomes prepared from the SMT-2A tumor have a sixfold higher sialyltransferase activity than do microsomes prepared from the nonmetastasizing mammary tumor MT-W9B [7].
• A rat brain Golgi sialyltransferase activity capable of the differentiation-dependent control of N-CAM sialylation state is described [8].

Chemical compound and disease context of St6gal1

• Towards understanding the mechanism of regulation of sialic acid levels upon cellular transformation, we have studied the regulation of expression of beta-galactoside alpha 2,6-sialyltransferase in a rat tumor, the Zajdela ascitic hepatoma [9].
• Studies of monokines as mediators of the acute phase response: effects on sialyltransferase, albumin, alpha 1-acid glycoprotein and beta-N-acetylhexosaminidase [10].
• Treatment of partially purified alpha 2,3 sialytransferase by peptide-N-glycosidase F showed a significative inhibition demonstrating that N-glycan moiety is required for complete activity of the C6 glioma cell alpha 2,3 sialyltransferase [11].
• Using synchronized C6 glioma cells, we showed that the alpha 2,3 sialyltransferase activity was inhibited by tunicamycin to a greater extend than DNA and protein biosynthesis suggesting inhibition of N-glycosylation of this enzyme [11].
• Hepatoma induced by feeding Wistar rats with 3'-methyl-4-dimethylaminoazobenzene (MeDAB) was more active than Wistar liver in sialylating asialo-orosomucoid, and this was due to an increased activity of Gal(beta 1----4)GlcNAc (alpha 2----6) sialyltransferase, the major sialyltransferase in these tissues [12].

Biological context of St6gal1

• Tissue-specific alternative splicing of the beta-galactoside alpha 2,6-sialyltransferase gene [13].
• These and supporting results show that soluble forms of the sialyltransferase can be generated by proteolytic cleavage between the NH2-terminal signal-anchor and the catalytic domain [14].
• Sialyltransferase sequences residing upstream of this transcriptional initiation point are used to control chloramphenicol acetyltransferase expression in fusion constructs following transient transfection into H35 cells to demonstrate the presence of a functional promoter [15].
• Although no element with similarity to the known GRE consensus sequence resides within this promoter region, chloramphenicol acetyltransferase expression under the control of the sialyltransferase promoter is subject to a low (1.6-fold) but reproducible induction in response to dexamethasone [15].
• In contrast, the predominant kidney mRNAs from this gene share only three coding exons that specify the carboxyl terminal 42% of the liver sialyltransferase protein sequence [16].

Anatomical context of St6gal1

• We previously found that BACE1 also cleaved a membrane-bound sialyltransferase, ST6Gal I. By BACE1 overexpression in COS cells, the secretion of ST6Gal I markedly increased, and the amino terminus of the secreted ST6Gal I started at Glu(41) [17].
• Immunofluorescence microscopy showed that although the wild type sialyltransferase is properly localized in the Golgi apparatus, the inactive cysteine mutants are retained in the endoplasmic reticulum [18].
• Because the sialyltransferase activities are associated with the Golgi complex, the cytoplasm appears compartmentalized into components which biogenetically involve the Golgi apparatus and components which do not [19].
• None of the membranes contain sialyltransferase, a Golgi membrane marker [20].
• In goblet cells the limiting membrane and lumen of forming and mature mucus droplets as well as the plasma membrane exhibited label for sialyltransferase [21].

Associations of St6gal1 with chemical compounds

• By means of nuclear run-off assays and measurement of nuclear unprocessed transcripts we demonstrate that dexamethasone induction of beta-galactoside alpha 2,6-sialyltransferase mRNA in rat Reuber H35 cells is mediated by a transcriptional enhancement mechanism [15].
• The beta-galactoside alpha-2,6-sialyltransferase represents a member of a family of sialyltransferases which catalyze the terminal addition of sialic acid to maturing carbohydrate chains [22].
• Primary structure of beta-galactoside alpha 2,6-sialyltransferase. Conversion of membrane-bound enzyme to soluble forms by cleavage of the NH2-terminal signal anchor [14].
• In this report we use the glucocorticoid agonist, RU362, and the antagonist, RU486, to demonstrate the participation of the glucocorticoid receptor pathway in beta-galactoside alpha 2,6-sialyltransferase regulation [15].
• Orientation of glycoprotein galactosyltransferase and sialyltransferase enzymes in vesicles derived from rat liver Golgi apparatus [23].

Regulatory relationships of St6gal1

• Rabbit antibodies raised to the Gal beta 1 to 4GlcNAc alpha 2 to 6 sialyltransferase inhibit its enzymatic activity greater than 99% but caused little or no inhibition of Gal beta 1 to 3(4)GlcNAc alpha 2 to 3 sialytransferase [24].

Other interactions of St6gal1

• This report describes the primary structure of a rat liver beta-galactoside alpha 2,6-sialyltransferase (EC 2.4.99.1), a Golgi apparatus enzyme involved in the terminal sialylation of N-linked carbohydrate groups of glycoproteins [14].
• To investigate the mechanism of carbocisteine action, we evaluated the effects of carbocisteine on the activity of fucosidase, sialidase, fucosyltransferase and sialyltransferase, and on the expression of Muc5ac mRNA in the airway epithelium of SO(2)-exposed rats [25].
• Developmental control of N-CAM sialylation state by Golgi sialyltransferase isoforms [8].
• The work suggests that a major portion of sialyltransferase containing the catalytic site is released from a membrane anchor by a cathepsin D-like proteinase located at the luminal face of the Golgi and that this explains the acute-phase behaviour of this enzyme [26].
• The activities of CMP-NeuAc synthase, N-acetyl-D-glucosamine 2-epimerase, N-acetyl-D-glucosamine kinase, sialyltransferase and sialidase were similar to or 2-4-fold lower than in liver [27].

Analytical, diagnostic and therapeutic context of St6gal1

• Hepatic sialyltransferase probes hybridize to mRNAs of varying size on Northern blots [22].
• These results show that the serum sialyltransferase alters its activity in conjunction with changes in tumor burden [28].
• Polymerase chain reaction cloning of a developmentally regulated member of the sialyltransferase gene family [29].
• The Gal beta 1 to 3(4)GlcNAc alpha 2 to 3 sialyltransferase was also purified further by CDP elution from CDP-agarose, but final purification required affinity chromatography on an adsorbent prepared by coupling asialoprothrombin to cyanogen bromide-activated agarose [24].
• To determine which amino-terminal regions are required for Golgi apparatus localization, mutant sialyltransferase proteins were constructed by in vitro oligonucleotide-directed mutagenesis, expressed in Cos-1 cells, and localized by indirect immunofluorescence microscopy [30].

References