Intra-Golgi Transport Inhibition by Megalomicin (*)
- From the (1)Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid 28049, Spain and the
- (2)MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, United Kingdom
- §To whom correspondence should be addressed: Centro de Biología Molecular, Universidad Autónoma de Madrid, Cantoblanco, Madrid 28049, Spain. Tel.: 341-3978049; Fax: 341-3978344.
Abstract
Megalomicin (MGM) is a macrolide antibiotic which has been demonstrated previously to cause an anomalous glycosylation of viral proteins. Here we show that MGM produces profound alterations on Golgi morphology and function. The addition of MGM at 50 μM for 1 h caused a dilation of the Golgi detected by immunofluorescence staining for medial- and trans-Golgi markers. The effect of MGM was clearly more intense on the trans-side of the Golgi, as evidenced in electron microscope preparations. The effect on Golgi morphology was reversible and correlated with an impairment of glycoprotein processing in the trans-Golgi. Thus, although the vesicular stomatitis virus G protein was processed in the presence of MGM to an endoglycosidase H-resistant form, it was poorly sialylated. The sialylation of cellular proteins was also inhibited, resulting in cells with low level of sialylation on the cell surface. However MGM did not inhibit the activities of the galactosyl- or sialyltransferase as measured in vitro. MGM inhibited cis- to medial-, and more strongly, medial- to trans-Golgi transport of vesicular stomatitis virus G protein in an in vitro system, suggesting that the impairment in glycoprotein maturation observed in vivo is the result of intra-Golgi transport inhibition.
Footnotes
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↵* This work was supported by grants from the Fondo de Investigaciones Sanitarias (94/0280), the Comunidad de Madrid (AE13/95), the European Union Biotech Program (BIOCT920164), and from the Fundación Ramón Areces. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵1 The abbreviations used are:
- ER
-
endoplasmic reticulum
- BFA
-
brefeldin A
- β-COP
-
coatomer protein β
- endo-H
-
endoglycosidase H
- HSV
-
herpes simplex virus
- IQ
-
ilimaquinone
- MGM
-
megalomicin
- NRK
-
normal rat kidney cells
- VSV
-
vesicular stomatitis virus
- DMEM
-
Dulbecco's modified Eagle's medium
- PBS
-
phosphate-buffered saline
- CHO
-
Chinese hamster ovary
- BHK
-
baby hamster kidney.
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↵2P. Bonay and B. Alarcón, unpublished results.
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- Received June 29, 1995.
- Revision received November 1, 1995.
- © 1996 by The American Society for Biochemistry and Molecular Biology, Inc.
