Mitochondrial Control by DRP1 in Brain Tumor Initiating Cells

Brain tumor initiating cells (BTICs) coopt the neuronal high affinity GLUT3 glucose transporter to withstand metabolic stress. Here, we investigated another mechanism critical to brain metabolism, mitochondrial morphology. BTICs displayed mitochondrial fragmentation relative to non-BTICs, suggesting that BTICs have increased mitochondrial fission. The essential mediator of mitochondrial fission, dynamin-related protein 1 (DRP1), was activated in BTICs and inhibited in non-BTICs. Targeting DRP1 using RNA interference or pharmacologic inhibition induced BTIC apoptosis and inhibited tumor growth. Downstream, DRP1 activity regulated the essential metabolic stress sensor, AMP-activated protein kinase (AMPK), and AMPK targeting rescued the effects of DRP1 disruption. Cyclin-dependent kinase 5 (CDK5) phosphorylated DRP1 to increase its activity in BTICs, whereas Ca(2+)–calmodulin-dependent protein kinase 2 (CAMK2) inhibited DRP1 in non-BTICs, suggesting tumor cell differentiation induces a regulatory switch in mitochondrial morphology. DRP1 activation correlates with poor prognosis in glioblastoma, suggesting mitochondrial dynamics may represent a therapeutic target for BTICs.