Cooperative function of the CHD5-like protein Mdm39p with a P-type ATPase Spf1p in the maintenance of ER homeostasis in Saccharomyces cerevisiae
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Spf1p is a P-type ATPase that is mainly localized to the endoplasmic reticulum (ER) in Saccharomyces cerevisiae. The protein is involved in the maintenance of ion homeostasis in the ER. To investigate the intracellular role of Spf1p in more detail, we performed a genetic screen for mutations that lead to synthetic lethality in combination with a disruption of SPF1; the mutations identified have been termed lws (for lethal with spf1) mutations. Mutant alleles of five LWS genes (MDM39, RIC1, LAS21, TUP1 and BTS1) were recovered. The identification of these genes provides clues to the physiological relationships between Spf1p function and the secretory pathway. Among the five genes identified, MDM39 encodes a membrane protein that is similar to the protein CHD5/WRB, which is involved in the pathogenesis of Down syndrome-associated congenital heart disease in humans. We localized Mdm39p to the ER. The Δmdm39 mutant exhibited defects in glycosylation, cell wall organization and the unfolded protein response. It also showed calcium-related phenotypes and synthetic lethal interactions with deletion mutations in other LWS genes. Our findings imply a homeostatic role for Mdm39p, which may be related to the regulation of calcium ion fluxes in the ER, and is indispensable for mutants that lack Spf1p.
KeywordsEndoplasmic reticulum membrane Ion homeostasis Killer toxin P-type ATPase Unfolded protein response (UPR)
This work was supported in part by the Cooperative System for Supporting Priority Research of the Japan Science and Technology Agency. We thank Dr K. Isono for providing yeast strains, Dr Y. Ohya for providing the yeast genomic library, Drs. R.D. Gietz, J.H. Hegemann, K. Mori, Y. Noda and E. Schiebel for providing plasmids, Dr M. Tokunaga for providing antibodies, and Dr J. Shima for participating in critical discussions.
- Benachour A, Sipos G, Flury I, Reggiori F, Canivenc-Gansel E, Vionnet C, Conzelmann A, Benghezal M (1999) Deletion of GPI7, a yeast gene required for addition of a side chain to the glycosylphosphatidylinositol (GPI) core structure, affects GPI protein transport, remodeling, and cell wall integrity. J Biol Chem 274:15251–15261PubMedGoogle Scholar
- Burke D, Dawson D, Stearns T (2000) Methods in yeast genetics. Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NYGoogle Scholar
- Dürr G, Strayle J, Plemper R, Elbs S, Klee SK, Catty P, Wolf DH, Rudolph HK (1998) The medial-Golgi ion pump Pmr1 supplies the yeast secretory pathway with Ca2+ and Mn2+ required for glycosylation, sorting, and endoplasmic reticulum-associated protein degradation. Mol Biol Cell 9:1149–1162PubMedGoogle Scholar
- Sambrook J, Fritsch EF, Maniatis T (1989) Molecular cloning: a laboratory manual, 2nd edn. Cold Spring Harbor Laboratory, Cold Spring Harbor, NYGoogle Scholar
- Suzuki C (2004) Acidophilic structure and killing mechanism of the Pichia farinosa killer toxin SMKT. Top Curr Genet 11:189–214Google Scholar
- Vidal-Taboada JM, Bergonon S, Sanchez M, Lopez-Acedo C, Groet J, Nizetic D, Egeo A, Scartezzini P, Katsanis N, Fisher EM, Delabar JM, Oliva R (1998) High resolution physical mapping and identification of transcribed sequences in the Down syndrome region-2. Biochem Biophys Res Commun 243:572–578CrossRefPubMedGoogle Scholar