Mol Cell Biol, February 1998, p. 1125-1135, Vol. 18, No. 2
Respiratory Medicine Unit,
Received 12 May 1997/Returned for modification 26 June
1997/Accepted 23 October 1997
Quantitative immunoelectron microscopy and subcellular
fractionation established the site of endoplasmic reticulum (ER)-Golgi transport arrest induced by the phosphatase inhibitor okadaic acid
(OA). OA induced the disappearance of transitional element tubules and
accumulation of the anterograde-transported Chandipura (CHP) virus G
protein only in the rough ER (RER) and not at more distal sites. The
block was specific to the early part of the anterograde pathway,
because CHP virus G protein that accumulated in the intermediate
compartment (IC) at 15°C could gain access to Golgi stack enzymes. OA
also induced RER accumulation of the IC protein p53/p58 via an IC-RER
recycling pathway which was resistant to OA and inhibited by the G
protein activator aluminium fluoride. The role of COPII coats in OA
transport block was investigated by using immunofluorescence and cell
fractionation. In untreated cells the COPII coat protein sec 13p
colocalized with p53/p58 in Golgi-IC structures of the juxtanuclear
region and peripheral cytoplasm. During OA treatment, p53/p58
accumulated in the RER but was excluded from sec 13p-containing
membrane structures. Taken together our data indicate that OA induces
an early defect in RER export which acts to prevent entry into
COPII-coated structures of the IC region.
0270-7306/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Okadaic Acid Induces Selective Arrest of Protein
Transport in the Rough Endoplasmic Reticulum and Prevents Export into
COPII-Coated Structures
*
Corresponding author. Mailing address: Medical Science
Institute, University of Dundee, Dundee DD1 4HN, Scotland, United
Kingdom. Phone: 01382 344973. Fax: 01382 345507. E-mail:
jlucocq{at}bad.dundee.ac.uk.
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