Invariant Chain Induces a Delayed Transport from Early to Late Endosomes (*)
- From the (1)Centre d'Immunologie INSERM-CNRS de Marseille Luminy, Case 906, 13288 Marseille Cedex 9, France and
- the (2)Division of Molecular Cell Biology, Department of Biology, University of Oslo, N 0316 Oslo, Norway
- §§ To whom correspondence should be addressed. Tel.: 47-22855787; Fax: 47-22854605; obakke{at}bio.uio.no
Abstract
Invariant chain associated with class II molecules is proteolytically processed in several distinct intermediates during its
transport through the endocytic pathway. Using subcellular fractionation, early and late endosomal compartments were separated
in human fibroblasts transfected with HLA-DR (4N5 cells) and supertransfected with invariant chain (4N5Ii cells) or invariant
chain lacking most of the cytoplasmic tail (4N5Δ20Ii cells). Early and late endosome membrane fractions were characterized
by morphology and by analyzing the presence of the Rab5 and Rab7 GTPases as markers of early and late endosomes, respectively.
The transfer of endocytosed horseradish peroxidase from early to late endosomes proceeded relatively rapid both in 4N5 and
4N5Δ20Ii cells (t
= 25 min), whereas this transfer was significantly delayed (t
= 2 h) in 4N5Ii cells. Pulse-chase experiments showed that invariant chain and its degradation products were first observed
in early endosomes and thereafter in late endosomes. Our results strongly suggest that invariant chain induces a retention
mechanism in the endocytic pathway.
Footnotes
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↵§ Supported by a fellowship from the Norwegian Research Council.
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↵¶ Supported by a fellowship from the Ministère de la Recherche et de la Technologie.
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↵** Supported by a fellowship from the Norwegian Cancer Society.
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↵* This work was financed by grants from the Norwegian Research Council, the Norwegian Cancer Society, the Association de la Recherche contre le Cancer (ARC), and the Ligue Fran¸aise Nationale contre le Cancer (LFNCC). 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:
- MHC
-
major histocompatibility complex
- FCS
-
fetal calf serum
- HRP
-
horseradish peroxidase
- PNS
-
post-nuclear supernatants
- PAGE
-
polyacrylamide gel electrophoresis
- PBS
-
phosphate-buffered saline.
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- Received September 12, 1994.
- © 1995 by The American Society for Biochemistry and Molecular Biology, Inc.
