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Proliferation of intracellular structures upon overexpression of the PMA2 ATPase in Saccharomyces cerevisiae
P Supply1, A Wach, D Thinès-Sempoux
1Unité de Biochimie Physiologique, Université Catholique de Louvain, Louvain-La-Neuve, Belgium.
Abstract:
The PMA2 gene is a presumed isogene of the PMA1 gene, encoding the major yeast plasma membrane H(+)-ATPase. When controlled by its own promoter, PMA2 in multiple copies does not complement a deficient PMA1 gene. Under the control of the PMA1 promoter, however, and expressed on a centromeric plasmid in yeast strains specially designed for stable expression, the PMA2 gene replaces the PMA1 gene to some extent, allowing growth on standard medium but not on acidic media. Plasma membranes of cells expressing only the PMA2 enzyme display low ATPase activity correlating with low amounts of PMA2 protein. This low activity is maintained throughout growth and does not increase when overexpression is favored by increased gene dosage. Immunoelectron microscopy reveals a dramatic proliferation of intracellular structures (probably endoplasmic reticulum) in which overexpressed PMA2 protein accumulates. Overexpression of PMA1 ATPase causes a similar phenomenon, but quantitative effects are lower compared to PMA2. These results indicate that the PMA2 gene encodes a functional plasma membrane H(+)-ATPase and suggest a specific control of the intracellular traffic of plasma membrane ATPase.
Insights
The PMA2 gene encodes a functional yeast plasma membrane H(+)-ATPase. However, it shows limited function and accumulates in intracellular structures when overexpressed, unlike the PMA1 gene.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- The PMA1 gene encodes the primary yeast plasma membrane H(+)-ATPase.
- The PMA2 gene is a related isogene with an incompletely understood function.
Purpose of the Study:
- To investigate the functionality and regulation of the yeast PMA2 gene.
- To compare the expression and activity of PMA2 with PMA1 under various conditions.
Main Methods:
- Yeast genetics: gene expression and complementation studies.
- Biochemical assays: measuring H(+)-ATPase activity.
- Immunoelectron microscopy: visualizing protein localization.
Main Results:
- PMA2 complements PMA1 deficiency partially, enabling growth on standard but not acidic media.
- Cells expressing PMA2 exhibit low plasma membrane H(+)-ATPase activity, correlating with low protein levels.
- Overexpression of PMA2 leads to accumulation in intracellular structures, likely the endoplasmic reticulum, a phenomenon also observed with PMA1 but to a lesser extent.
Conclusions:
- The PMA2 gene encodes a functional plasma membrane H(+)-ATPase.
- Intracellular trafficking and specific regulation control the activity of plasma membrane ATPases like PMA2.