Chs7p, a New Protein Involved in the Control of Protein Export from the Endoplasmic Reticulum That Is Specifically Engaged in the Regulation of Chitin Synthesis in Saccharomyces cerevisiae

• Published in: The Journal of cell biology Vol. 145; no. 6; pp. 1153 - 1163
• Main Authors: Trilla, Jose A., Durán, Angel, Roncero, Cesar
• Format: Journal Article
• Language: English
• Published: United States Rockefeller University Press 14.06.1999; The Rockefeller University Press
• Subjects: Amino Acid Sequence; Benzenesulfonates; Cell Fractionation; Cell walls; Cells; Cellular biology; Chitin; Chitin - analogs & derivatives; Chitin - biosynthesis; Chitin - metabolism; Chitin Synthase - genetics; Chitin Synthase - metabolism; Chitosan; Cloning, Molecular; Diploidy; Endoplasmic Reticulum - metabolism; Fungal Proteins - chemistry; Fungal Proteins - genetics; Fungal Proteins - metabolism; Fungal Proteins - physiology; Gene Deletion; Gene expression regulation; Gene Expression Regulation, Fungal - drug effects; Genes; Genes, Fungal - genetics; Genes, Fungal - physiology; Genetic Complementation Test; Immunohistochemistry; Mating Factor; Membrane Proteins - chemistry; Membrane Proteins - genetics; Membrane Proteins - metabolism; Membrane Proteins - physiology; Molecular Chaperones; Molecular Sequence Data; Peptides - metabolism; Peptides - pharmacology; Phenotype; Plasmids; Proteins; Recombinant Fusion Proteins - analysis; Recombinant Fusion Proteins - biosynthesis; Recombinant Fusion Proteins - metabolism; RNA, Messenger - genetics; RNA, Messenger - metabolism; Saccharomyces cerevisiae; Saccharomyces cerevisiae - drug effects; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - growth & development; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins; Sporulation; Yeast; Yeasts
• ISSN: 0021-9525; 1540-8140
• DOI: 10.1083/jcb.145.6.1153

The Saccharomyces cerevisiae CHS7 gene encodes an integral membrane protein located in the ER which is directly involved in chitin synthesis through the regulation of chitin synthase III (CSIII) activity. In the absence of CHS7 product, Chs3p, but not other secreted proteins, is retained in the ER, leading to a severe defect in CSIII activity and consequently, to a reduced rate of chitin synthesis. In addition, chs7 null mutants show the yeast phenotypes associated with a lack of chitin: reduced mating efficiency and lack of the chitosan ascospore layer, clear indications of Chs7p function throughout the S. cerevisiae biological cycle. CHS3 overexpression does not lead to increased levels of CSIII because the Chs3p excess is retained in the ER. However, joint overexpression of CHS3 and CHS7 increases the export of Chs3p from the ER and this is accompanied by a concomitant increase in CSIII activity, indicating that the amount of Chs7p is a limiting factor for CSIII activity. Accordingly, CHS7 transcription is increased when elevated amounts of chitin synthesis are detected. These results show that Chs7p forms part of a new mechanism specifically involved in Chs3p export from the ER and consequently, in the regulation of CSIII activity.