Endosomal sorting complexes required for transport (ESCRTs) are involved in the 
formation of multivesicular bodies and sorting of targeted proteins to the yeast 
vacuole. The deletion of seven genes encoding components of the ESCRT machinery 
render Saccharomyces cerevisiae cells sensitive to high extracellular CaCl2 
concentrations as well as to low pH in media. In this work, we focused on 
intracellular pH (pHin) homeostasis of these mutants. None of the studied ESCRT 
mutants exhibited an altered pHin level compared to the wild type under standard 
growth conditions. Nevertheless, 60 min of CaCl2 treatment resulted in a more 
significant drop in pHin levels in these mutants than in the wild type, 
suggesting that pHin homeostasis is affected in ESCRT mutants upon the addition 
of calcium. Similarly, CaCl2 treatment caused a bigger pHin decrease in cells 
lacking the vacuolar Ca(2+)/H(+) antiporter Vcx1 which indicates a role for this 
protein in the maintenance of proper pHin homeostasis when cells need to cope 
with a high CaCl2 concentration in media. Importantly, ESCRT gene deletions in 
the vcx1Δ strain did not result in an increase in the CaCl2-invoked drop in the 
pHin levels of cells, which demonstrates a genetic interaction between VCX1 and 
studied ESCRT genes.