This is a proposal to continue studies of Na,K-ATPase expression and function in the central nervous system (CNS). This enzyme controls ion gradients across plasma membranes, as well as the composition and volume of extracellular fluid. It consumes 50% of energy used in brain and 70% in retina. Since its several isoforms differ in substrate affinities and susceptibility to regulation, defining patterns of isoform expression is important to understanding roles of the enzyme in the CNS. This laboratory has developed antibodies specific for three isoforms of the Na,K-ATPase alpha subunit as well as for three beta subunit isoforms, and used these for localization studies in cerebellum and in cell culture. A third gamma subunit has been little studied. It is suggested that progress on the Human Genome Project will rapidly lead to identification of all subunit isoforms of this enzyme, as well as the related H,K-ATPases. In this context, the first aim of this proposal is to produce isoform-specific antibodies to all of the subunits expressed in the CNS, to determine their distributions by immunocytochemistry and confocal microscopy in brain, retina, cultured astrocytes, optic nerve and secretory structures such as choroid plexus and ciliary body. cDNAs for new subunits will be sequenced and characterized.
The second aim will investigate functional properties of different isoform combinations in mammalian cells and transfectants to answer questions about their physiological roles and to determine the molecular basis for astrocyte potassium transport properties.
The third aim i s to use a histochemical assay for Na,K-ATPase activity to detect activity of different isoforms in situ, and to test the hypothesis that reduced enzyme activity after ischemia is cell- and isoform-selective and important as a neuroprotective mechanism.
These aims will be accomplished using a combination of cellular, molecular and immunological methodologies.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
3R01NS027653-10S1
Application #
2909142
Study Section
Special Emphasis Panel (ZRG1 (01))
Program Officer
Jacobs, Tom P
Project Start
1989-08-01
Project End
2002-02-28
Budget Start
1998-07-15
Budget End
1999-02-28
Support Year
10
Fiscal Year
1999
Total Cost
Indirect Cost
Name
Massachusetts General Hospital
Department
Type
DUNS #
City
Boston
State
MA
Country
United States
Zip Code
02199
Ellis, Dorette Z; Rabe, Jason; Sweadner, Kathleen J (2003) Global loss of Na,K-ATPase and its nitric oxide-mediated regulation in a transgenic mouse model of amyotrophic lateral sclerosis. J Neurosci 23:43-51
Moseley, Amy E; Lieske, Steve P; Wetzel, Randall K et al. (2003) The Na,K-ATPase alpha 2 isoform is expressed in neurons, and its absence disrupts neuronal activity in newborn mice. J Biol Chem 278:5317-24
Feschenko, Marina S; Donnet, Claudia; Wetzel, Randall K et al. (2003) Phospholemman, a single-span membrane protein, is an accessory protein of Na,K-ATPase in cerebellum and choroid plexus. J Neurosci 23:2161-9
Feschenko, Marina S; Stevenson, Elizabeth; Nairn, Angus C et al. (2002) A novel cAMP-stimulated pathway in protein phosphatase 2A activation. J Pharmacol Exp Ther 302:111-8
Wetzel, R K; Sweadner, K J (2001) Immunocytochemical localization of NaK-ATPase isoforms in the rat and mouse ocular ciliary epithelium. Invest Ophthalmol Vis Sci 42:763-9
Ellis, D Z; Nathanson, J A; Rabe, J et al. (2001) Carbachol and nitric oxide inhibition of Na,K-ATPase activity in bovine ciliary processes. Invest Ophthalmol Vis Sci 42:2625-31
Sweadner, K J; Feschenko, M S (2001) Predicted location and limited accessibility of protein kinase A phosphorylation site on Na-K-ATPase. Am J Physiol Cell Physiol 280:C1017-26
Ellis, D Z; Nathanson, J A; Sweadner, K J (2000) Carbachol inhibits Na(+)-K(+)-ATPase activity in choroid plexus via stimulation of the NO/cGMP pathway. Am J Physiol Cell Physiol 279:C1685-93
Sweadner, K J; Rael, E (2000) The FXYD gene family of small ion transport regulators or channels: cDNA sequence, protein signature sequence, and expression. Genomics 68:41-56
Feschenko, M S; Stevenson, E; Sweadner, K J (2000) Interaction of protein kinase C and cAMP-dependent pathways in the phosphorylation of the Na,K-ATPase. J Biol Chem 275:34693-700

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