Intracellular pH is a tightly controlled signal in yeast

Background: Nearly all processes in living cells are pH dependent, which is why intracellular pH (pHi) is a tightly regulated physiological parameter in all cellular systems. However, in microbes such as yeast, pHi responds to extracellular conditions such as the availability of nutrients. This raises the question of how pHi dynamics affect cellular function.
Scope of review: We discuss the control of pHi, and the regulation of processes by pHi, focusing on the model organism Saccharomyces cerevisiae. We aim to dissect the effects of pHi on various aspects of cell physiology, which are often intertwined. Our goal is to provide a broad overview of how pHi is controlled in yeast, and how pHi in turn controls physiology, in the context of both general cellular functioning as well as of cellular decision making upon changes in the cell's environment.
Major conclusions: Besides a better understanding of the regulation of pHi, evidence for a signaling role of pHi is accumulating. We conclude that pHi responds to nutritional cues and relays this information to alter cellular make-up and physiology. The physicochemical properties of pH allow the signal to be fast, and affect multiple regulatory levels simultaneously.
General significance: The mechanisms for regulation of processes by pHi are tightly linked to the molecules that are part of all living cells, and the biophysical properties of the signal are universal amongst all living organisms, and similar types of regulation are suggested in mammals. Therefore, dynamic control of cellular decision making by pHi is therefore likely a general trait.
Research highlights: ► pHi affects the properties of almost all molecules in living cells. ► Intracellular pH is highly dynamic and varies in response to environmental change. ► pHi is tightly controlled in separate organelles. ► Cytosolic pH functions as a signal to relay nutritional cues.