Calmodulin kinase 2 genetically interacts with Rch1p to negatively regulate calcium import into Saccharomyces cerevisiae after extracellular calcium pulse.

After a single extracellular 100 mM calcium pulse (final concentration), wild type S. cerevisiae exhibits a sharp peak in cytosolic calcium. The concentration drops rapidly in these cells as the calcium is sequestered away in the endoplasmic reticulum, Golgi, and vacuoles leaving resting cytosolic levels higher than their original state, followed by changes in gene expression. In cells lacking calmodulin kinase 2 (Cmk2p), a secondary rise in cytosolic calcium concentration is seen after extracellular calcium increases and the cytosolic calcium is subsequently sequestered. Utilizing double deletions, we demonstrate that Cmk2p is modulating the activity of Rch1p, a known inhibitor of Channel X which is a yeast plasma membrane channel through which calcium ions are transported after an extracellular calcium pulse. We hypothesize that Cmk2p is acting as a regulator of Channel X by activating Rch1p and without CMK2, Channel X inactivation does not occur fully.

Energy Metabolism Regulates Stem Cell Pluripotency.

Pluripotent stem cells (PSCs) are characterized by their unique capacity for both unlimited self-renewal and their potential to differentiate to all cell lineages contained within the three primary germ layers. While once considered a distinct cellular state, it is becoming clear that pluripotency is in fact a continuum of cellular states, all capable of self-renewal and differentiation, yet with distinct metabolic, mitochondrial and epigenetic features dependent on gestational stage. In this review we focus on two of the most clearly defined states: "naïve" and "primed" PSCs. Like other rapidly dividing cells, PSCs have a high demand for anabolic precursors necessary to replicate their genome, cytoplasm and organelles, while concurrently consuming energy in the form of ATP. This requirement for both anabolic and catabolic processes sufficient to supply a highly adapted cell cycle in the context of reduced oxygen availability, distinguishes PSCs from their differentiated progeny. During early embryogenesis PSCs adapt their substrate preference to match the bioenergetic requirements of each specific developmental stage. This is reflected in different mitochondrial morphologies, membrane potentials, electron transport chain (ETC) compositions, and utilization of glycolysis. Additionally, metabolites produced in PSCs can directly influence epigenetic and transcriptional programs, which in turn can affect self-renewal characteristics. Thus, our understanding of the role of metabolism in PSC fate has expanded from anabolism and catabolism to include governance of the pluripotent epigenetic landscape. Understanding the roles of metabolism and the factors influencing metabolic pathways in naïve and primed pluripotent states provide a platform for understanding the drivers of cell fate during development. This review highlights the roles of the major metabolic pathways in the acquisition and maintenance of the different states of pluripotency.