Sec24 Proteins and Sorting at the Endoplasmic Reticulum*
- Alessandra Pagano,
- François Letourneur‡,
- David Garcia-Estefania§,
- Jean-Louis Carpentier,
- Lelio Orci and
- Jean-Pierre Paccaud¶
- From the Department of Morphology, University Medical Center,§Department of Zoology, Geneva University, Geneva CH-1211, Switzerland and the ‡Institute of Biology and Chemistry of Proteins, CNRS, Lyon, 69367 France
Abstract
COPII proteins are necessary to generate secretory vesicles at the endoplasmic reticulum. In yeast, the Sec24p protein is the only COPII component in which two close orthologues have been identified. By using gene knock-out in yeast, we found that the absence of one of these Sec24 orthologues resulted in a selective secretion defect for a subset of proteins released into the medium. Data base searches revealed the existence of an entire family of Sec24-related proteins in humans, worms, flies, and plants. We identified and cloned two new human cDNAs encoding proteins homologous to yeast Sec24p, in addition to two human cDNAs already present within the data bases. The entire Sec24 family identified to date is characterized by clusters of highly conserved residues within the 2/3 carboxyl-terminal domain of all the proteins and a divergent amino terminus domain. Human (h) Sec24 orthologues co-immunoprecipitate with hSec23Ap and migrate as a complex by size exclusion chromatography. Immunofluorescence microscopy confirmed that these proteins co-localize with hSec23p and hSec13p. Together, our data suggest that in addition to its role in the shaping up of the vesicle, the Sec23-24p complex may be implicated in cargo selection and concentration.
Footnotes
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↵* This work was supported by the Helmut Horten Stiffung, the Sandoz Foundation, the de Reuter Foundation, the Julius Thorn Overseas Trust (to J. P. P.), Swiss National Science Foundation Grant 31-43366/2, the Human Frontier Science Program (to L. O.), the Association pour la Recherche Contre le Cancer, and the Fondation pour la Recherche Médicale (to F. L.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵¶ To whom correspondence should be addressed. Tel.: 41-22-7025238; Fax: 41-22-7025260; E-mail: paccaud{at}cmu.unige.ch.
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↵2 A. Pagano, F. Letourneur, D. Garcia-Estefania, J.-L. Carpentier, L. Orci, and J.-P. Paccaud, unpublished results.
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↵3 T. Yoshihisa and R. Schekman, personal communication.
- Abbreviations:
- ER
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endoplasmic reticulum
- ORF
-
open reading frame
- aa
-
amino acids
- FITC
-
fluorescein isothiocyanate
- bp
-
base pair
- PCR
-
polymerase chain reaction
- RT
-
room temperature
- PBS
-
phosphate-buffered saline
- h
-
human
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- Received December 9, 1998.
- The American Society for Biochemistry and Molecular Biology, Inc.
