Changes in metabolic proteins in ex vivo rat retina during glutamate-induced neural progenitor cell induction

Understanding how energy metabolism and related proteins influence neural progenitor cells in adult tissues is critical for developing new strategies in clinical tissue regeneration therapy. We have recently reported that a subtoxic concentration of glutamate-induced neural progenitor cells in the mature ex vivo rat retina. We herein explore changes in the metabolic pathways during the process. We firstly observed an increase in lactate and lactate dehydrogenase concentration in the glutamate-treated retina. We then investigated the levels of glycolytic enzymes and confirmed significant upregulation of pyruvate kinase M type (PKM), especially PKM2, enolase, phosphoglycerate mutase 1 (PGAM1), and inosine-5'-monophosphate dehydrogenase (IMPDH1) in the glutamate-treated retina compared to the untreated retina. An analysis of the subcellular localization of PKM2 revealed nuclear translocation in the treated retina, which has been reported to regulate cell cycle proliferation and glycolytic enzymes. Our findings indicate that the mature rat retina undergoes an increase in aerobic glycolysis. PKM2, both in the cytoplasm and in the nucleus, may thus play an important role during neural progenitor cell induction, as it does in other proliferating cells.