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PMID: 10662773 Published · ppublish English Journal Article Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, P.H.S.

Apg9p/Cvt7p is an integral membrane protein required for transport vesicle formation in the Cvt and autophagy pathways.

The Journal of cell biology ·Vol. 148 ·No. 3 ·2000-02-07 ·Pages 465-80

Noda T, Kim J, Huang WP, Baba M, Tokunaga C, Ohsumi Y, Klionsky DJ

Abstract

In nutrient-rich, vegetative conditions, the yeast Saccharomyces cerevisiae transports a resident protease, aminopeptidase I (API), to the vacuole by the cytoplasm to vacuole targeting (Cvt) pathway, thus contributing to the degradative capacity of this organelle. When cells subsequently encounter starvation conditions, the machinery that recruited precursor API (prAPI) also sequesters bulk cytosol for delivery, breakdown, and recycling in the vacuole by the autophagy pathway. Each of these overlapping alternative transport pathways is specifically mobilized depending on environmental cues. The basic mechanism of cargo packaging and delivery involves the formation of a double-membrane transport vesicle around prAPI and/or bulk cytosol. Upon completion, these Cvt and autophagic vesicles are targeted to the vacuole to allow delivery of their lumenal contents. Key questions remain regarding the origin and formation of the transport vesicle. In this study, we have cloned the APG9/CVT7 gene and characterized the gene product. Apg9p/Cvt7p is the first characterized integral membrane protein required for Cvt and autophagy transport. Biochemical and morphological analyses indicate that Apg9p/Cvt7p is localized to large perivacuolar punctate structures, but does not colocalize with typical endomembrane marker proteins. Finally, we have isolated a temperature conditional allele of APG9/CVT7 and demonstrate the direct role of Apg9p/Cvt7p in the formation of the Cvt and autophagic vesicles. From these results, we propose that Apg9p/Cvt7p may serve as a marker for a specialized compartment essential for these vesicle-mediated alternative targeting pathways.

MeSH Terms
Animals Autophagy/physiology Biological Transport Centrifugation, Density Gradient Fungal Proteins/genetics,metabolism Membrane Proteins/genetics,metabolism Rabbits Saccharomyces cerevisiae/genetics,metabolism,physiology Subcellular Fractions Vacuoles/metabolism
Chemicals
Fungal Proteins Membrane Proteins
Authors & Affiliations
7 authors, click to expand affiliations / ORCID
Noda T
Department of Cell Biology, National Institute for Basic Biology, Okazaki 444-8585, Japan.
Kim J
Huang W P
Baba M
Tokunaga C
Ohsumi Y
Klionsky D J
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Article Info
Journal
The Journal of cell biology
Abbr.
J Cell Biol
ISSN
0021-9525
DOI
10.1083/jcb.148.3.465
Published
2000-02-07
Pages
465-80
Language
English
Region
United States
NLM ID
0375356
PMCID
PMC2174799
Subset
IM
Grants
NIGMS NIH HHS · GM53396 · United States
External Links
PubMed source DOI: 10.1083/jcb.148.3.465 PMC Full Text View journal details
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