Recent developments in probing the levels and flux of selected organellar cations as well as organellar mechanosensitivity

Electrochemical gradients exist not only across the plasma membrane (PM) but also across membranes of organelles. Various endomembrane-localised ion channels and transporters have been identified, the activity of which is critical for organellar (and also cellular) ionic homeostasis that underpins diverse cellular processes. Aberrant organellar ion flux underlies several diseases, identifying organellar channels and transporters as potential drug targets. Therefore, the need for probing the functions of these proteins in situ cannot be overemphasised. The acidic interior of a few organelles as well as the dynamic nature of most organelles historically presented challenges for reliable estimation of luminal ionic concentrations. But there have been significant methodological and technical advancements by now, allowing measurement of levels of specific ions within these organelles as well as their flux across endomembranes with increasing precision. Evidence also continues to amass reporting mechanosensitivity of the endomembranes and its physiological significance. Here we highlight some recent developments in tools and techniques for measuring the levels and movement of some selected organellar cations as well as organellar mechanosensitivity.