Topoisomerase 1 inhibition reversibly impairs synaptic function

• Published in: Proceedings of the National Academy of Sciences - PNAS 2014-12, Vol.111 (48), p.17290-17295
• Main Authors: Mabb, Angela M., Kullmann, Paul H. M., Twomey, Margaret A., Miriyala, Jayalakshmi, Philpot, Benjamin D., Zylka, Mark J.
• Format: Article
• Language: English
• Subjects: Action Potentials - drug effects; Animals; Autistic disorder; Biological Sciences; Brain; Cancer; Cell Adhesion Molecules, Neuronal - metabolism; Cells, Cultured; Cerebral Cortex - cytology; DNA Topoisomerases, Type I - metabolism; Excitatory Postsynaptic Potentials - drug effects; Excitatory Postsynaptic Potentials - physiology; Female; Gene expression; Gene expression regulation; Genes; Immunoblotting; Mice, Inbred C57BL; Microscopy, Fluorescence; Neural Cell Adhesion Molecules - metabolism; Neurons; Neurons - drug effects; Neurons - metabolism; Neurons - physiology; Neurotransmission; Neurotransmitters; Patch-Clamp Techniques; Proteins; Receptors; Synapses; Synapses - drug effects; Synapses - physiology; Synaptic transmission; Topoisomerase I Inhibitors - pharmacology; Topotecan - pharmacology; Vehicles
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1413204111

Topotecan is a topoisomerase 1 (TOP1) inhibitor that is used to treat various forms of cancer. We recently found that topotecan reduces the expression of multiple long genes, including many neuronal genes linked to synapses and autism. However, whether topotecan alters synaptic protein levels and synapse function is currently unknown. Here we report that in primary cortical neurons, topotecan depleted synaptic proteins that are encoded by extremely long genes, including Neurexin-1 , Neuroligin-1 , Cntnap2 , and GABA Aβ3 . Topotecan also suppressed spontaneous network activity without affecting resting membrane potential, action potential threshold, or neuron health. Topotecan strongly suppressed inhibitory neurotransmission via pre- and postsynaptic mechanisms and reduced excitatory neurotransmission. The effects on synaptic protein levels and inhibitory neurotransmission were fully reversible upon drug washout. Collectively, our findings suggest that TOP1 controls the levels of multiple synaptic proteins and is required for normal excitatory and inhibitory synaptic transmission. Significance Topoisomerases are enzymes that resolve DNA supercoiling during cell division and gene transcription. Inhibitors of these enzymes are used to treat multiple forms of cancer. Recently we found that topoisomerase inhibitors have profound effects on synaptic genes expressed in the brain. Here we examine the contribution of a clinically used topoisomerase inhibitor on the expression of synaptic proteins and synaptic transmission. We find that inhibition of topoisomerase 1 (TOP1) dampens excitatory and inhibitory synaptic transmission in cortical neurons. Additionally, these effects are fully reversible, because synaptic protein levels and synaptic transmission recover upon washout of the TOP1 inhibitor. These findings provide insights into how inhibition of TOP1 impacts synaptic function in neurons.