Abstract
Metabolic studies of human pluripotent stem cells (hPSCs) have focused on how the cells produce energy through the catabolic pathway. The less-studied anabolic pathway, by which hPSCs expend energy in the form of adenosine triphosphate (ATP), is not yet fully understood. Compared to fully differentiated somatic cells, hPSCs undergo significant changes not only in their gene expression but also in their production and/or expenditure of ATP. Here, we investigate how hPSCs tightly control their energy homeostasis by studying the main energy-consuming process, mRNA translation. In addition, change of subcellular organelles regarding energy homeostasis has been investigated. Lysosomes are organelles that play an important role in the elimination of unnecessary cellular materials by digestion and in the recycling system of the cell. We have found that hPSCs control their lysosome numbers in part by regulating lysosomal gene/protein expression. Thus, because the levels of mRNA translation rate are lower in hPSCs than in somatic cells, not only the global translational machinery but also the lysosomal recycling machinery is suppressed in hPSCs. Overall, the results of our study suggest that hPSCs reprogram gene expression and signaling to regulate energy-consuming processes and energy-controlling organelles.