Genetic and Phenotypic Overlap between Autophagy and the Cytoplasm to Vacuole Protein Targeting Pathway

doi:10.1074/jbc.271.30.17621

Genetic and Phenotypic Overlap between Autophagy and the Cytoplasm to Vacuole Protein Targeting Pathway*

From the Section of Microbiology, University of California, Davis, California 95616 and the
^‡ Institut für Biochemie, Universität Stuttgart, 70569 Stuttgart, Germany

^§ To whom correspondence should be addressed. Tel.: 916-752-0277; Fax: 916-752-9014; E-mail: djklionsky{at}ucdavis.edu

Abstract

We have explored the phenotypic and genetic overlap between autophagocytosis and cytoplasm to vacuole targeting in the yeast Saccharomyces cerevisiae. Complementation analysis was performed with mutants in each of these groups (aut and cvt, respectively), and three complementation groups were found to overlap. Also, most of the unique aut mutants accumulated precursor aminopeptidase I in the cytoplasm, while maintaining wild type kinetics and maturation of proteins targeted to the vacuole via the secretory pathway. The majority of the non-overlapping cvt mutants were found to be at least partially defective in autophagy. Some mutants in each group, however, appear to be only marginally affected in the other phenotype, implying that these pathways only partially overlap. We propose that import of aminopeptidase I into the vacuole shares a number of components required for bulk autophagocytosis, but is made specific, saturable, and constitutive by the presence of a receptor or other interacting protein(s).

Footnotes

↵* This work was supported by a National Science Foundation Graduate Research Fellowship (to T. M. H.), a National Institutes of Health Molecular and Cellular Biology Training Grant (to A. H.-G.), Grant Wo210/12-1 from the Deutsche Forschungsgemeinschaft (to M. T.), and Public Health Service Grant GM53396 from the National Institutes of Health (to D. J. K.). 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.
↵¹ The abbreviations used are:

ER

endoplasmic reticulum

API

aminopeptidase I

aut

autophagy

CPY

carboxypeptidase Y

cvt

cytoplasm to vacuole targeting

EMS

ethyl methanesulfonate

PGK

phosphoglycerate kinase

PrA

proteinase A

PrB

proteinase B

PVDF

polyvinylidene difluoride

PMSF

phenylmethylsulfonyl fluoride

PAGE

polyacrylamide gel electrophoresis.
↵² Y. Suriapranata, unpublished results.
↵³ M. Straub and M. Thumm, unpublished results.
- Received April 1, 1996.
- Revision received April 26, 1996.