Abstract
Through a genome-wide screen we have identified calcium-tolerant deletion mutants for five genes in the budding yeast Saccharomyces cerevisiae. In addition to CNB1 and RCN1 that are known to play a role in the calcium signalling pathway, the protein kinase gene CMK2, the sphingolipid homeostasis-related gene ORM2 and the gene SIF2 encoding the WD40 repeat-containing subunit of Set3C histone deacetylase complex are involved in the calcium sensitivity of yeast cells to extracellular calcium. Cmk2 and the transcription factor Crz1 have opposite functions in the response of yeast cells to calcium stress. Deletion of CMK2 elevates the level of calcium/calcineurin signalling and increases the expression level of PMR1 and PMC1, which is dependent on Crz1. Effects of Cmk2 on calcium sensitivity and calcium/calcineurin signalling are dependent on its kinase activity. Therefore, Cmk2 is a negative feedback controller of the calcium/calcineurin signalling pathway. Furthermore, the cmk2 crz1 double deletion mutant is more resistant than the crz1 deletion mutant, suggesting that Cmk2 has an additional Crz1-independent role in promoting calcium tolerance.
Highlights
Calcium ions regulate many cellular processes in both prokaryotes and eukaryotes [1,2,3,4,5]
We revealed that deletion of CNB1, RCN1, CMK2, ORM2 or SIF2 caused yeast cells to be tolerant to 0.4 M CaCl2, and these phenotypes were more dramatical in the presence of 0.6 M CaCl2 (Fig. 1)
Our observation that deletion of CNB1 leads to a calcium-tolerant phenotype in the wild type BY4743 background is consistent with previous studies [33, 34], showing that inactivation of calcineurin including deletion of CNB1 restores the calcium-tolerance of yeast cells lacking PMC1, since calcineurin decreases calcium tolerance of pmc1 cells by inhibiting the function of the vacuolar H+/Ca2+ exchanger Vcx1
Summary
Calcium ions regulate many cellular processes in both prokaryotes and eukaryotes [1,2,3,4,5]. Regulation of intracellular calcium homeostasis and the calcium/calcineurin signalling pathway are highly conserved in eukaryotic cells [6, 7]. In the budding yeast Saccharomyces cerevisiae, cytosolic calcium homeostasis is regulated by Ca2+ transporters and sequestrators in the plasma and organellar membranes. Transient increases in cytosolic Ca2+ activate the calcium/ calcineurin signalling pathway. Sustained Ca2+ accumulation in the cytosol is prevented by a Ca2 sequestration system composed of the calcium pump Pmc and the Ca2 +/H+ exchanger Vcx in the vacuolar membrane as well as the calcium pump Pmr and the Ca2+/H+ exchanger Gdt in the ER/Golgi secretory pathway [8,9,10].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
