Chaperone Function of a Grp 94-related Protein for Folding and Transport of the Pancreatic Bile Salt-dependent Lipase (*)
- From the (1) From INSERM Unité 260, Faculté de Médecine Timone, 27 boulevard Jean Moulin, 13385 Marseille Cedex 05, France
- ¶ To whom correspondence should be addressed: INSERM U-260, Faculté de Médecine Timone, 27 Blvd. Jean Moulin, 13385 Marseille Cedex 05, France. Tel.: 33-91-83-44-02; Fax: 33-91-83-01-87.
Abstract
In its fundamental attributes, the secretion pathway of the pancreatic bile salt-dependent lipase (BSDL) followed that described for all enzymes involved in regulated secretion. This route was inhibited by drugs that affect protein synthesis and intracellular transport. In the presence of monensin, BSDL was solely detected in microsome membrane fractions. The association of BSDL with intracellular membranes involved a protein complex, formed by at least two proteins of 94 and 56 kDa. In cells experiencing the metabolic stress due to azetidine-2-carboxylic acid, BSDL was additionally associated with a protein of 46 kDa. Affinity blotting showed that BSDL bound directly to the 94-kDa protein (p94). It was suggested that p94 could be a molecular chaperone, further identified as related to the 94-kDa glucose regulated protein (Grp 94). The membrane-associated BSDL (i.e. BSDL bound to the Grp 94-related p94) was O- and N-glycosylated and consequently appeared released from membranes in the trans-Golgi compartment. Therefore and for the first time, it is suggested that a multiprotein complex including the chaperone Grp 94-related p94 protein may play an essential role in the folding and transport of BSDL. One hypothesis is that the association of BSDL with membrane via the Grp 94-related p94 along its secretion pathway is required for its complete O-glycosylation, which occurs on the extended mucin-like structures present on the C-terminal part of the protein.
Footnotes
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↵§ Recipient of a fellowship from the ARC.
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↵* This work was supported by grants from the Association pour la Recherche sur le Cancer (ARC, Villejuif, France) and the Conseil Général des Bouches-du-Rhône (Marseille, France). 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 Abbreviations used:
- BSDL
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bile salt-dependent lipase (EC 3.1.1.-)
- Grp
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glucose-regulated protein
- Hsp
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heat shock protein
- Endo H
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endoglycosidase H (EC 3.2.1.96).
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↵2N. Bruneau, P. Lechne, V. Sbarra, and D. Lombardo, unpublished results.
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↵3N. Bruneau and D. Lombardo, unpublished results.
- © 1995 by The American Society for Biochemistry and Molecular Biology, Inc.
