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J. Biol. Chem., Vol. 281, Issue 46, 35057-35069, November 17, 2006
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From the Departament de Bioquímica i Biologia Molecular, Edificio V, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Barcelona, Catalonia, Spain
Type 2C protein phosphatases are encoded in Saccharomyces cerevisiae by several related genes (PTC1-5 and PTC7). To gain insight into the functions attributable to specific members of this gene family, we have investigated the transcriptional profiles of ptc1-5 mutants. Two main patterns were obtained as follows: the one generated by the ptc1 mutation and the one resulting from the lack of Ptc2-5. ptc4 and ptc5 profiles were quite similar, whereas that of ptc2 was less related to this group. Mutation of PTC1 resulted in increased expression of numerous genes that are also induced by cell wall damage, such as YKL161c, SED1, or CRH1, as well as in higher amounts of active Slt2 mitogen-activated protein kinase, indicating that lack of the phosphatase activates the cell wall integrity pathway. ptc1 cells were even more sensitive than slt2 mutants to a number of cell wall-damaging agents, and both mutations had additive effects. The sensitivity of ptc1 cells was not dependent on Hog1. Besides these phenotypes, we observed that calcineurin was hyperactivated in ptc1 cells, which were also highly sensitive to calcium ions, heavy metals, and alkaline pH, and exhibited a random haploid budding pattern. Remarkably, many of these traits are found in certain mutants with impaired vacuolar function. As ptc1 cells also display fragmented vacuoles, we hypothesized that lack of Ptc1 would primarily cause vacuolar malfunction, from which other phenotypes would derive. In agreement with this scenario, overexpression of VPS73, a gene of unknown function involved in vacuolar protein sorting, largely rescues not only vacuolar fragmentation but also sensitivity to cell wall damage, high calcium, alkaline pH, as well as other ptc1-specific phenotypes.
Received for publication, August 18, 2006 , and in revised form, September 13, 2006.
* This work was supported in part by Grant MIRG-CT-2004-003794 from the European Commission and Grants BFU2004-00014 (to A. C.), BMC2002-04011-C05-04, and BFU2005-06388-C4-04-BMC (to J. A.) from the Ministerio de Educación y Ciencia, Spain, and Fondo Europeo de Desarrollo Regional. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
The on-line version of this article (available at http://www.jbc.org) contains supplemental Tables 1 and 2.
1 Both authors contributed equally to this work.
2 Recipient of a fellowship from the Spanish Ministry of Education and Science.
3 Recipient of a fellowship from the Generalitat de Catalunya, Spain.
4 Recipient of a fellowship from the Spanish Ministry of Education and Science.
5 Recipient of an "Ajut de Suport a les Activitats dels Grups de Recerca" Grant 2005SGR-00542 from the Generalitat de Catalunya.
6 To whom correspondence should be addressed. Tel.: 34-93-5811649; Fax: 34-93-5812006; E-mail: Antonio.Casamayor{at}uab.es.
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