Effect of GTP on the dolichol pathway for protein glycosylation in rat liver microsomes

Incubation of native rat liver microsomes with GTP resulted in enhanced incorporation of N-acetylglucosamine (GlcNAc) from UDP-GlcNAc into lipid acceptors. The stimulation of GlcNAc transfer by GTP was specific for GTP; ATP exerted no effect. The GTP effect was blocked by a non-hydrolysable GTP anal...

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Bibliographic Details
Published in:Biochemical journal 1993-12, Vol.296 (3), p.633-637
Main Authors: BOSSUYT, X, BLANCKAERT, N
Format: Article
Language:English
Subjects:
Acetylglucosamine - metabolism
Animals
Biological and medical sciences
Cell Membrane Permeability
Cell physiology
Dolichol - metabolism
Endoplasmic Reticulum - metabolism
Fundamental and applied biological sciences. Psychology
Glycoproteins - metabolism
Glycosides - metabolism
Glycosylation
Guanosine Triphosphate - pharmacology
Microsomes, Liver - drug effects
Microsomes, Liver - metabolism
Molecular and cellular biology
N-Acetylglucosaminyltransferases - metabolism
Rats
Responses to growth factors, tumor promotors, other factors
Transferases (Other Substituted Phosphate Groups) - metabolism
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Summary:Incubation of native rat liver microsomes with GTP resulted in enhanced incorporation of N-acetylglucosamine (GlcNAc) from UDP-GlcNAc into lipid acceptors. The stimulation of GlcNAc transfer by GTP was specific for GTP; ATP exerted no effect. The GTP effect was blocked by a non-hydrolysable GTP analogue guanosine 5'-[beta gamma-imido]triphosphate, indicating that GTP hydrolysis was crucial. Though dolichyl pyrophosphate NN'-diacetylchitobiose [Dol-PP-(GlcNAc)2] was the main radiolabelled product formed upon incubation of GTP-treated microsomes with UDP-GlcNAc, GTP selectively stimulated UDP-GlcNAc:dolichyl phosphate (Dol-P) N-acetylglucosaminyl 1-phosphotransferase (N-acetylglucosaminyl 1-phosphotransferase). This conclusion was reached on the basis of experiments in which tunicamycin was used to selectively inhibit N-acetylglucosaminyl 1-phosphotransferase. The enhanced transformation of Dol-P to dolichyl pyrophosphate N-acetylglucosamine (Dol-PP-GlcNAc) by GTP ultimately led to enhanced protein glycosylation. GTP-induced stimulation of GlcNAc incorporation in lipid and protein by GTP was observed also in microsomes fully permeabilized with Staph. aureus alpha-toxin. These findings refute the previous proposal [Godelaine, Beaufay, Wibo and Ravoet (1983) J. Cell Biol. 97, 340-350] that increased membrane permeability constitutes the mechanism whereby GTP activates the reactions of the dolichol pathway.
ISSN:0264-6021
1470-8728
DOI:10.1042/bj2960633