Action potentials are generated at the axon initial segment (AIS) and are propagated via saltatory conduction at nodes of Ranvier. These domains are highly enriched in voltage gated Na+ channels, which form a multimeric complex with beta subunits, neuronal cell adhesion molecules, notably neurofascin (NF) 186, and the cytoskeletal proteins ankyrin G and piv spectrin. We have recently demonstrated that targeting of NF186 to PNS nodes is mediated via its extracellular interactions, that it has an essential role in node formation by recruiting ankyrin G via its cytoplasmic domain, and that ankyrin G in turn, is required for the accumulation of sodium channels. In contrast, ankyrin accumulation at initial segments, which is also critical for domain organization is intrinsically specified, independent of NF186. These studies raise a number of key questions. What is the source of proteins targeted to the node and how do they traffic to this site? Are nodal components, once assembled, stably expressed at the node or do they continuously turnover and, if so, is this turnover enhanced by demyelination? Finally, do CNS nodes assemble like PNS nodes (i.e. directed by extracellular signals) or more akin to initial segments (i.e. directed from the inside-out via interactions with ankyrin G)? In this proposal, we address these questions and further characterize mechanisms of node assembly by: i) determining how proteins traffic to PNS nodes, including whether they are recruited from cell surface pools or via directed vesicular transport, ii) live image nodes to examine dynamic changes that occur during development and with demyelination, and iii) examine the dependence of CNS nodes on NF186- dependent signals in cocultures and targeting signals in transgenic mice. These studies should provide important new insights into the axo-glial interactions that regulate the assembly and maintenance of nodes of Ranvier. They will also be an important foundation for elucidating pathogenetic changes at nodes that result from demyelination.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS043474-08
Application #
7794972
Study Section
Special Emphasis Panel (ZRG1-MDCN-F (02))
Program Officer
Kleitman, Naomi
Project Start
2002-04-01
Project End
2012-03-31
Budget Start
2010-04-01
Budget End
2011-03-31
Support Year
8
Fiscal Year
2010
Total Cost
$367,074
Indirect Cost
Name
New York University
Department
Microbiology/Immun/Virology
Type
Schools of Medicine
DUNS #
121911077
City
New York
State
NY
Country
United States
Zip Code
10016
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