Characterization of Gdt1p, a yeast protein localized in the Golgi apparatus and involved in calcium homeostasis
(2013)
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- Authors
- Supervisors
- Morsomme, Pierre
- Abstract
- Calcium (Ca2+) is a ubiquitous and versatile intracellular messenger involved in many different processes. Basically, Ca2+ signalling requires the maintenance of a low cytosolic concentration (usually 50-200 nM). Upon stimulation, the signals are generated by the massive entry of Ca2+ from internal and/or external stores. Ca2+ signalling is therefore strongly dependent on a complex toolkit of pumps/exchangers and channels localized in the different compartments of the cells and responsible for the outwards and inwards fluxes, respectively. In this work, we addressed the function of a previously uncharacterized family of membrane proteins, called UPF0016. An in depth bioinformatic analysis highlighted the high level of conservation found between members of the family, but allowed us to classify them into eight different subfamilies based on some specific features. We then decided to focus on the yeast S. cerevisae member of the family, Gdt1p. We showed that Gdt1p is localized in the cis- and medial-Golgi apparatus, where it colocalizes with Pmr1p, the yeast Ca2+/Mn2+-ATPase. Our findings indicate that Gdt1p and Pmr1p are involved in two different, but related, pathways of Ca2+ transport in the Golgi apparatus. Simultaneous deletion of both genes leads to a strong sensitivity to high external Ca2+ concentration, perturbations of Golgi functions and intolerance to Ca2+ starvation. Furthermore, the pmr1Δ/gdt1Δ double deletant shows a growth defect on non preferred carbon sources (e.g. galactose, mannose, ethanol, or glycerol), indicating a link between Ca2+ homeostasis and adaptation of the carbon metabolism. Our current hypothesis is that Gdt1p, and the other members of the UPF0016 family, are directly involved in Ca2+ transport, probably as a novel family of Ca2+/H+ exchangers. Of course, this hypothesis needs to be confirmed by direct transport assays, which requires improvement of the purification procedure presented in the last part of this work.
- Affiliations
Citations
Demaegd, D. (2013). Characterization of Gdt1p, a yeast protein localized in the Golgi apparatus and involved in calcium homeostasis. https://hdl.handle.net/2078.5/200222