Diversity in intrinsic neuronal excitability is generated by the variable expression, subcellular localization, and function of a complex repertoire of ion channels. Dynamic regulation of intrinsic excitability can further alter the behavior of neurons and confer plasticity to neuronal signaling. Aberrant expression, localization, and function of ion channels can result in channel-based pathophysiologies. One of the challenging questions is to understand how neurons regulate the expression and localization of ion channels.
The Axon Inital Segment AIS and the nodes of Ranvier are key sub-compartments that generate and conduct the action potentials along the axon. The voltage-dependent sodium Nav and potassium Kv channels are critically concentrated at the AIS and nodes of Ranvier to ensure proper axon potential propagation. Despite the central role of these channels in excitability, the molecular and cellular determinants governing their appropriate targeting and membrane organization are just beginning to emerge.
An intricate assembly of adhesion molecules and cytoskeletal scaffold proteins hold Nav and Kv channels in place. However, how such a complex is dynamically regulated is still largely unknown. We recently identified two new processes based on phosphorylation of Nav and Kv complexes by two kinases, casein kinase 2 CK2 and cyclin-dependant kinase Cdks. The end-results of this proposal should provide new insights into the mechanisms involved in the dynamic regulation of excitability and opens new paths to better understand defects leading to neuronal dysfunction.
Field of Science inorganic compounds. Activity type Higher or Secondary Education Establishments. Status Closed project. Start date 1 July End date 30 June Neuronal architecture in health and disease European researchers investigated the structure of neurons in normal and abnormal conditions. Discover other articles in the same domain of application. Diversity in intrinsic neuronal excitability and function is generated by the variable expression, subcellular localization, and activity of a complex repertoire of neuronal ion channels.
Moreover, aberrant expression, localization, and function of ion channels can result in channel-based pathophysiologies. Thus, an understanding of how neurons regulate the expression and localization of ion channels is critical to understanding the complexity of normal neuronal function, its dynamic modulation to achieve plasticity, and defects that lead to neuronal dysfunction. This is where voltage-dependent sodium Nav and potassium Kv channels are critically concentrated to ensure proper axon potential propagation.
At the molecular level, Nav and Kv channels are held in place by an intricate assembly of adhesion molecules, and cytoskeletal scaffold proteins.
Despite the crucial role of Kv1 and Nav1 channels in neuronal physiology and of ankG in axonal organization, the molecular and cellular determinants governing their appropriate targeting and assembly are just beginning to emerge. We recently identified two new processes based on the phosphorylation Nav and Kv complexes by two kinases: casein kinase 2 CK2 and cyclin-dependant kinase Cdks. In this project, there are three specific aims that I intended to accomplish with a multidisciplinary approach during the four-year funding period: i Aim 1: Molecular dissection of the CK2 pathway in regulating AIS component clustering; ii Aim 2: Role of Cdk signaling in Kv1 localization and clustering at the AIS; iii Aim 3: Characterization of the mechanisms regulating ion channel targeting and clustering at the Node of Ranvier.
At the end of the funding period, we showed for the first time, that Nav1 channels are phosphorylated in vivo in their ankG-binding motif using a phosphospecific antibody that we developed against serine of this motif. This phosphorylation follows Nav1 expression levels during neuronal development. The existence of such complexes likely leads to Nav1-phosphorylation during neuronal development and, consequently, Nav1—membrane anchoring by enhanced binding to ankG article currently being written.
These results were published in the Journal of Cellular Biology in We showed that ankG targeting to the axon of hippocampal neurons is regulated by the kinase CDK5 and by its serine rich domain.
Department of Zoology
Understanding these mechanisms is one of the most basic and essential questions in biology. Moreover, recent studies are beginning to give us new views concerning the structure of axonal compartments, which are not as static and uniform as once thought. They are actually diverse and dynamic in order to produce a fine-tuning of neuronal excitability in normal and pathological conditions. Therefore, the identification of our new molecular mechanisms will also help to understand neuronal physiology in normal and pathological contexts.
Chinese Science Bulletin. Effect of optic nerve stimulation on bipolar cell in the carp retina. Novel GABAc receptors. Differential effects of low calcium on signal transmission from rods and cones to horizontal cells in carp retina. Sheng Li Hsueh Pao 48 , Ohno, K.
Wang , M. Milone, N. Bren, J. Brengman, S.
Nakano, P. Quiram, J. Pruitt, S. Sine and E. Congential myasthenic syndrome caused by decreased agonist binding affinity due to a mutation in the acetylcholine receptor e subunit. Neuron , Engel, A. Ohno, M. Milone, H. Wang , S. Nakano, C. Bouzat, J. Pruitt II, D. Hutchinson, J. Brengman, N. Sieb and S. Sine: New mutations in acetylcholine receptor subunit genes reveal heterogeneity in the slow-channel congenital myasthenic syndrome. Human Molecular Genetics 5: , Human Molecular Genetics 6: , Wang, H-L.
Ion channels in health and disease - PhD course in NEUROBIOLOGY
Mutation in the M1 domain of the acetylcholine receptor a subunit decreases the rate of agonist dissociation. Journal of General Physiology , Milone, M. Slow channel myasthenic syndrome caused by enhanced activation, desensitization, and agonist binding affinity due to mutation in the M2 domain of the acetylcholine receptor a subunit. Journal of Neuroscience ,