RT Journal Article
T1 Nuclear proteasomal degradation of Saccharomyces cerevisiae inorganic pyrophosphatase Ipp1p, a nucleocytoplasmic protein whose stability depends on its subcellular localization.
A1 Serrano-Bueno, Gloria
A1 Madroñal, Juan Manuel
A1 Manzano-López, Javier
A1 Muñiz, Manuel
A1 Pérez-Castiñeira, José Román
A1 Hernández, Agustín
A1 Serrano, Aurelio
K1 Cell nucleus
K1 Inorganic pyrophosphatase
K1 Nucleocytoplasmic transport
K1 Protein degradation
K1 Ubiquitin-proteasome system
AB Inorganic pyrophosphate (PPi) is an abundant by-product of cellular metabolism. PPi-producing reactions take place in the nucleus concurrently with reactions that use PPi as a substrate. Saccharomyces cerevisiae possesses two soluble pyrophosphatases (sPPases): Ipp1p, an essential and allegedly cytosolic protein, and Ipp2p, a mitochondrial isoenzyme. However, no sPPase has yet been unambiguously described in the nucleus. In vivo studies with fluorescent fusions together with activity and immunodetection analyses demonstrated that Ipp1p is a nucleocytoplasmic protein. Mutagenesis analysis showed that this sPPase possesses a nuclear localization signal which participates in its nuclear targeting. Enforced nucleocytoplasmic targeting by fusion to heterologous nuclear import and export signals caused changes in polypeptide abundance and activity levels, indicating that Ipp1p is less stable in the nucleus that in the cytoplasm. Low nuclear levels of this sPPase are physiologically relevant and may be related to its catalytic activity, since cells expressing a functional nuclear-targeted chimaera showed impaired growth and reduced chronological lifespan, while a nuclear-targeted catalytically inactive protein was not degraded and accumulated in the nucleus. Moreover, nuclear proteasome inhibition stabilized Ipp1p whereas nuclear targeting promoted its ubiquitination and interaction with Ubp3p, a component of the ubiquitin-proteasome system. Overall, our results indicate that Ipp1p is nucleocytoplasmic, that its stability depends on its subcellular localization and that sPPase catalytic competence drives its nuclear degradation through the ubiquitin-proteasome system. This suggests a new scenario for PPi homeostasis where both nucleocytoplasmic transport and nuclear proteasome degradation of the sPPase should contribute to control nuclear levels of this ubiquitous metabolite.
YR 2019
FD 2019-02-28
LK http://hdl.handle.net/10668/13650
UL http://hdl.handle.net/10668/13650
LA en
DS RISalud
RD Apr 18, 2025