Ykt6p, a Prenylated SNARE Essential for Endoplasmic Reticulum-Golgi Transport

doi:10.1074/jbc.272.28.17776

Ykt6p, a Prenylated SNARE Essential for Endoplasmic Reticulum-Golgi Transport*

From the Cellular Biochemistry and Biophysics Program and the^§Molecular Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10021

Abstract

Vesicular transport between secretory compartments requires specific recognition molecules called SNAREs. Here we report the identification of three putative SNAREs, p14 (Sft1p), p28 (Gos1p), and a detailed characterization of p26 (Ykt6p). All three were originally isolated as interacting partners of the cis Golgi target membrane-associated SNARE Sed5p, when Sec18p (yeast NSF) was inactivated. YKT6 is an essential gene that codes for a novel vesicle-associated SNARE functioning at the endoplasmic reticulum-Golgi transport step in the yeast secretory pathway. Depletion of Ykt6p results in the accumulation of the p1 precursor (endoplasmic reticulum form) of the vacuolar enzyme carboxypeptidase Y and morphological abnormalities consistent with a defect in secretion. Membrane localization of Ykt6p is essential for protein function and is normally mediated by isoprenylation. However, replacement of the isoprenylation motif with a bona fide transmembrane anchor results in a functional protein confirming that membrane localization, but not isoprenylation per se, is required for function. Ykt6p and its homologues are highly conserved from yeast to human as demonstrated by the functional complementation of the loss of Ykt6p by its human counterpart. This is the first example of a human SNARE protein functionally replacing a yeast SNARE. This observation implies that the specific details of the vesicle targeting code, like the genetic code, are conserved in evolution.

Footnotes

↵* This work was supported by National Institutes of Health Postdoctoral Fellowship GM17722 (to J. A. M.), a National Institutes of Health Fogarty Fellowship (to M. S.), National Institutes of Health grants (to J. E. R.), and National Science Foundation grant DB1-9420123 (to P. T.). The Memorial Sloan-Kettering Cancer Center Microchemistry Facility is supported by National Cancer Institute Core Grant 5 P30 CA08748.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.
↵‡ Present address: National Food Research Inst., 2-1-2 Kannondai, Tsukuba, Ibakaki 305, Japan.
↵¶ To whom correspondence should be addressed: Cellular Biochemistry and Biophysics Program, Memorial Sloan-Kettering Cancer Center, 1275 York Ave., New York, NY 10021. Fax: 212-717-3604.
↵1 The abbreviations used are: v-SNARE, vesicle-associated SNARE; t-SNARE, target membrane-associated SNARE; CPY, carboxypeptidase Y; ER, endoplasmic reticulum; PCR, polymerase chain reaction; ORF, open reading frame; EST, expressed sequence tag; PAGE, polyacrylamide gel electrophoresis; VAMP, vesicle-associated membrane protein.
↵2 The World Wide Web address ishttp://ulrec3.unil.ch.
↵3 M. Johnston et al., unpublished results.
↵4 J. McNew, J. G. S. Coe, M. Søgaard, T. Engel, T. H. Söllner, W. Hong, and J. E. Rothman, manuscript in preparation.
↵5 M. Craighead, T. H. Söllner, and J. E. Rothman, unpublished results.
- Received March 26, 1997.
- Revision received May 6, 1997.