The Saccharomyces cerevisiae Golgi Gdt1 protein is a Ca2+-Mn2+/H+ exchanger and its abundance is regulated by Ca2+ and Mn2+
(2022)
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- Authors
- Supervisors
- Morsomme, Pierre
- Abstract
- The Golgi apparatus is a major hub for post-translational modifications and for protein sorting. Accordingly, the preservation of Golgi structure and functionalities are everlasting tasks. It is ensured by mechanisms involving the control of luminal chemical composition and of lipid bilayer thickness, and is supported by structural and transport machineries at the cytosolic side of Golgi cisternae. Failings of those mechanisms usually lead to various cellular troubles, including glycosylation defects. In 2012, some congenital disorders of glycosylation were related to mutations of TMEM165 protein in human. As this protein was not characterized at that time, we started in our laboratory the study of Gdt1p, the Saccharomyces cerevisiae ortholog of TMEM165. It was demonstrated that Gdt1p is a Golgi-localized transmembrane protein able to transport Ca2+ and Mn2+ cations. Furthermore, GDT1 deletion is also characterized by Golgi trafficking defects and glycosylation troubles. The predicted topology of the protein matches with the usual topology of exchangers. In this study, we investigated two elements of Gdt1p physiological function, its transport mechanism and its regulation. Starting from the assumption that Gdt1p could exchange H+ ions against Ca2+ and Mn2+ cations across the Golgi membrane, we developed measurement strategies to assess it. A heterologous expression system using Lactococcus lactis was set up for direct H+ transport assay and a Golgi-localized pH sensor was developed for in vivo measurements in S. cerevisiae. Thanks to them, Gdt1p-mediated H+ transport activity was demonstrated. Then, we looked at Gdt1p regulation. We observed that Gdt1p is rapidly downregulated as a response to extracellular Mn2+ addition and that regulation occurs both at transcriptional and post-translational levels. The fast and efficient retrieval of Gdt1p from the Golgi membrane to be sorted to the vacuole probably occurs trough a novel degradation pathway.
- Affiliations
UCLouvain SST/LIBST - Louvain Institute of Biomolecular Science and Technology
Citations
Deschamps, A. (2022). The Saccharomyces cerevisiae Golgi Gdt1 protein is a Ca2+-Mn2+/H+ exchanger and its abundance is regulated by Ca2+ and Mn2+. https://hdl.handle.net/2078.5/271367