A 29-Kilodalton Golgi SolubleN-Ethylmaleimide-sensitive Factor Attachment Protein Receptor (Vti1-rp2) Implicated in Protein Trafficking in the Secretory Pathway*
- From the Membrane Biology Laboratory, Institute of Molecular and Cell Biology, Singapore 117609, Singapore
Abstract
Expressed sequence tags coding for a potential SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) were revealed during data base searches. The deduced amino acid sequence of the complete coding region predicts a 217-residue protein with a COOH-terminal hydrophobic membrane anchor. Affinity-purified antibodies raised against the cytoplasmic region of this protein specifically detect a 29-kilodalton integral membrane protein enriched in the Golgi membrane. Indirect immunofluorescence microscopy reveals that this protein is mainly associated with the Golgi apparatus. When detergent extracts of the Golgi membrane are incubated with immobilized glutathione S-transferase α soluble N-ethylmaleimide-sensitive factor attachment protein (GST-α-SNAP), this protein was specifically retained. This protein has been independently identified and termed Vti1-rp2, and it is homologous to Vti1p, a yeast Golgi SNARE. We further show that Vti1-rp2 can be qualitatively coimmunoprecipitated with Golgi syntaxin 5 and syntaxin 6, suggesting that Vti1-rp2 exists in at least two distinct Golgi SNARE complexes. In cells microinjected with antibodies against Vti1-rp2, transport of the envelope protein (G-protein) of vesicular stomatitis virus from the endoplasmic reticulum to the plasma membrane was specifically arrested at the Golgi apparatus, providing further evidence for functional importance of Vti1-rp2 in protein trafficking in the secretory pathway.
Footnotes
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↵* This work was funded by the Institute of Molecular and Cell Biology, National University of Singapore (to W. H.).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.
The nucleotide sequence(s) reported in this paper has been submitted to the GenBank™/EMBL Data Bank with accession number(s) AF035823.
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↵‡ To whom correspondence should be addressed: Institute of Molecular and Cell Biology, 30 Medical Dr., Singapore 117609, Singapore. Tel.: 65-778-6827; Fax: 65-779-1117; E-mail: mcbhwj{at}imcb.nus.edu.sg.
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↵2 S. H. Wong and W. H. Hong, manuscript in preparation.
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↵3 S. H. Wong and W.-J. Hong, unpublished observations.
- Abbreviations:
- NSF
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N-ethylmaleimide-sensitive factor
- SNAP
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soluble NSF attachment proteins
- SNARE
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SNAP receptor
- v-SNARE
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vesicle-associated SNARE
- t-SNARE
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target membrane SNARE
- ER
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endoplasmic reticulum
- EST
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expressed sequence tag
- GST
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glutathione S- transferase.
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- Received September 25, 1997.
- Revision received June 2, 1998.
- The American Society for Biochemistry and Molecular Biology, Inc.
