Premium
Steady‐state free Ca 2+ in the yeast endoplasmic reticulum reaches only 10 μM and is mainly controlled by the secretory pathway pump Pmr1
Author(s) -
Strayle Jochen,
Pozzan Tullio,
Rudolph Hans K.
Publication year - 1999
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/18.17.4733
Subject(s) - endoplasmic reticulum , aequorin , thapsigargin , biology , golgi apparatus , secretory pathway , organelle , yeast , microbiology and biotechnology , photoprotein , intracellular , biochemistry , bioluminescence
Over recent decades, diverse intracellular organelles have been recognized as key determinants of Ca 2+ signaling in eukaryotes. In yeast however, information on intra‐organellar Ca 2+ concentrations is scarce, despite the demonstrated importance of Ca 2+ signals for this microorganism. Here, we directly monitored free Ca 2+ in the lumen of the endoplasmic reticulum (ER) of yeast cells, using a specifically targeted version of the Ca 2+ ‐sensitive photoprotein aequorin. Ca 2+ uptake into the yeast ER displayed characteristics distinctly different from the mammalian ER. At steady‐state, the free Ca 2+ concentration in the ER lumen was limited to ∼10 μM, and ER Ca 2+ sequestration was insensitive to thapsigargin, an inhibitor specific for mammalian ER Ca 2+ pumps. In pmr1 null mutants, free Ca 2+ 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 Ca 2+ uptake activity in yeast.