Glutaminase 1 Is Essential for the Differentiation, Proliferation, and Survival of Human Neural Progenitor Cells

Abstract

Glutaminase is the enzyme that converts glutamine into glutamate, which serves as a key excitatory neurotransmitter and one of the energy providers for cellular metabolism. Previous studies have revealed that mice lacking glutaminase 1 (GLS1), the dominant isoform in the brain and kidney, died shortly after birth due to disrupted glutamatergic transmission, suggesting the critical role of GLS1 in the physiological functions of synaptic network. However, whether GLS1 regulates neurogenesis, a process by which neurons are generated from neural progenitor cells (NPCs), is unknown. Using a human NPC model, we found that both GLS1 isotypes, kidney-type glutaminase and glutaminase C, were upregulated during neuronal differentiation, which were correlated with the expression of neuronal marker microtubule-associated protein 2 (MAP-2). To study the functional impact of GLS1 on neurogenesis, we used small interference RNA targeting GLS1 and determined the expressions of neuronal genes by western blot, real-time polymerase chain reaction, and immunocytochemistry. siRNA silencing of GLS1 significantly reduced the expression of MAP-2, indicating that GLS1 is essential for neurogenesis. To unravel the specific process(es) of neurogenesis being affected, we further studied the proliferation and survival of NPCs in vitro. siRNA silencing of GLS1 significantly reduced the Ki67 + and increased the TUNEL + cells, suggesting critical roles of GLS1 for the proliferation and survival of NPCs. Together, these data suggest that GLS1 is critical for proper functions of NPCs, including neuronal differentiation, proliferation, and survival.

Glutamine Regulates Cardiac Progenitor Cell Metabolism and Proliferation

“…In different types of stem cells, Gln has been shown to be important for differentiation, survival and proliferation . In agreement with these observations we found that Gln had a strong stimulatory effect on CPC proliferation and promoted survival under conditions of oxidative stress.…”

Glutaminases in brain: Multiple isoforms for many purposes

“…Recently, it has been shown that, in a model of human neural progenitor cells, KGA and GAC were upregulated during neuronal differentiation and the siRNA silencing of GLS significantly reduced the expression of the neuronal marker microtubule-associated protein 2 (MAP-2), a protein proposed to regulate microtubule networks in neurons, suggesting that GLS is critical in neuronal differentiation and survival (Wang et al, 2014). Convergent evidence was obtained by using in vitro cultures of mouse embryonary cortical neurons: inhibition of GA activity blocked differentiation of these neurons (Velletri et al, 2013).…”

GLS loss of function causes autosomal recessive spastic ataxia and optic atrophy

“…Cultured neurons from the mice show a reduction in depolarization‐evoked glutamate release and altered excitatory postsynaptic potentials (EPSCs). In addition, it has been shown that knockdown of GLS in human neural progenitor cells (NPCs) leads to a significant reduction in NPC survival and ability to differentiate into neurons 11. Taken together, these findings would predict that complete loss of GLS expression would not be compatible with human growth and development.…”