Subcellular interactions between Ca2+ and cAMP in determining neuronal activity
Final Report Abstract
Neuroscientists have long sought to understand how circuits in the nervous system are organized to generate the precise neural outputs that underlie particular behaviours. Our research was (and is) focused on understanding mechanisms responsible for generation of the two rhythmic outputs, each having both fundamental and clinical importance. We examined one rhythm generator which is located to the brainstem and establishes stable breathing. Another 'rhythmic device' is responsible for intense oscillatory activity during epilepsy in the hippocampus. We applied up-todate methods of biophysics, neuroscience and genetics to examine the two neuronal networks. The integrated approach revealed special roles of the two second messengers, calcium and cAMP, in generation and maintenance of persistent rhythmic activity and their spatial organisation. Using one physiological (breathing) and one pathological (epilepsy) cases we examined how normal and pathological modes of activity in these networks are established and can be transformed into each other. The project met its aims and the main findings are (a) breathing rhythm is based on calcium waves in dendrites that excite pacemakers and produce stable motor output; (b) the respiratory network is self-tuned in response to environmental conditions via calcium-calmodulin kinase II; (c) Important role of cAMP in neurodevelopment is shown for Rett Syndrome. We suggest that cAMP-elevating medications are promising candidates to alleviate RTT symptoms and perhaps other neurodevelopmental diseases. (d) intracellular ATP shows marked depletion during epilepsy. Treatments that improve ATP homeostasis e. g. ketogenic diet (fasting) should counter epilepsy. This was been empirically established for a long time and now we provide molecular and cellular explanation of the effect. Briefly, in this project we visualized neurons in the respiratory and hippocampal networks with genetically encoded fluorescent sensors. Large-scale rhythmic network activity was monitored as fluctuations of calcium, cAMP and ATP within neurons. Such techniques did not exist before this project started. Now it is possible to depict multifactorial activities of whole networks of neurons and monitor their output in real-time in the intact brain tissue. The methods developed will have various fundamental and clinical implications.
Publications
- 2009. Imaging cytoplasmic cAMP in mouse brainstem neurons. BMC Neuroscience 10: 29-38
Mironov S, Skorova E, Taschenberger G, Nikolaev VO, Lohse MJ, Kügler S
- 2009. Remodelling of the respiratory network in a mouse model of Rett syndrome depends on brain-derived neurotrophic factor regulated slow calcium buffering. J Physiol 587: 2473-85
Mironov SL, Skorova E, Hartelt N, Mironova LA, Hasan MT, Kügler S
- 2009. Respiratory circuits: Topology, function, metabolism and pathology. Neuroscientist 15: 194-208
Mironov SL
- 2011. Epac-mediated cAMP-signalling in the mouse model of Rett Syndrome. Neuropharmacology 60: 869-77
Mironov SL, Skorova EY, Kügler S
- 2011. Stimulation of bursting in pre-Bötzinger neurons by Epac through calcium release and modulation of TRPM4 and K-ATP channels. J Neurochem. 117: 295-308
Mironov SL, Skorova EY
- 2013. Calmodulin and calmodulin kinase II mediate emergent bursting activity in the brainstem respiratory network (preBötzinger complex). J Physiol. 591: 1613-30
Mironov SL
(See online at https://doi.org/10.1113/jphysiol.2012.237362) - 2013. Single KATP channel opening in response to stimulation of AMPA/kainate receptors is mediated by Na accumulation and submembrane ATP and ADP changes. J Physiol. 591: 2593-609
Mollajew R, Toloe J, Mironov SL
(See online at https://doi.org/10.1113/jphysiol.2012.248369) - 2014. Metabolic differences in hippocampal 'Rett' neurons revealed by ATP imaging. Mol Cell Neurosci. 59: 47-56
Toloe J, Mollajew R, Kügler S, Mironov SL
(See online at https://doi.org/10.1016/j.mcn.2013.12.008)
