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- Title
Steady-state free Ca<sup>2+</sup> in the yeast endoplasmic reticulum reaches only 10 µM and is mainly controlled by the secretory pathway pump Pmr1.
- Authors
Strayle, Jochen; Pozzan, Tullio; Rudolph, Hans K.
- Abstract
Over recent decades, diverse intracellular organelles have been recognized as key determinants of Ca2+ signaling in eukaryotes. In yeast however, information on intra-organellar Ca2+ concentrations is scarce, despite the demonstrated importance of Ca2+ signals for this microorganism. Here, we directly monitored free Ca2+ in the lumen of the endoplasmic reticulum (ER) of yeast cells, using a specifically targeted version of the Ca2+-sensitive photoprotein aequorin. Ca2+ uptake into the yeast ER displayed characteristics distinctly different from the mammalian ER. At steady-state, the free Ca2+ concentration in the ER lumen was limited to ∼10 μM, and ER Ca2+ sequestration was insensitive to thapsigargin, an inhibitor specific for mammalian ER Ca2+ pumps. In pmr1 null mutants, free Ca2+ in the ER was reduced by 50%. Our findings identify the secretory pathway pump Pmr1, predominantly localized in the Golgi, as a major component of ER Ca2+ uptake activity in yeast.
- Publication
EMBO Journal, 1999, Vol 18, Issue 17, p4733
- ISSN
0261-4189
- Publication type
Academic Journal
- DOI
10.1093/emboj/18.17.4733