One long term objective is to understand the biochemical and cellular mechanisms of the regulation of the sodium pump (Na,K-ATPase), which is the driving force for cerebrospinal fluid (CSF) secretion. The other is to understand how that regulation is coordinated with the unique morphological changes in the secretory epithelium. We have data that indicate that phosphorylation events at the apical membrane coordinate the regulation of Na,K-ATPase with the regulation of secretory cell morphology. CSF is produced by the choroid plexuses in the brain's ventricles, and it flows out through other structures. Clinically when the outflow pathways are blocked, hydrocephalus (infants) or intracranial hypertension (adults) results. There are endogenous mechanisms that reduce Na,K-ATPase activity in the choroid plexus that we will investigate, including thirst, vasopressin, serotonin, and carbachol. The proposed research has three complementary thrusts.
The first aim uses the tools of biochemistry, primary cultures, and genetic manipulation of cells to test the hypothesis that choroid plexus Na,K-ATPase is regulated by kinase-mediated phosphorylation of an accessory protein, phospholemman (FXYD1), with a change in the kinetics of the enzyme. Comparison of cultures from wild type and phospholemman knockout mice will allow direct and indirect effects to be separated.
The second aim uses the tools of microscopy and biochemistry to investigate whether the regulation entails redistribution from microvilli to a subapical compartment.
The third aim uses wild type, phospholemman knockout, and hydrocephalic mice to test the hypothesis that phospholemman is an obligatory link to regulation of both Na,K-ATPase and choroid cell activation state.
The aims test several hypotheses: 1) that there is concerted regulation of Na,K-ATPase and morphological change at the apical brush border through macromolecular complexes; 2) that the phospholemman knockout mouse has defective responses to physiological signals to inhibit Na,K-ATPase and change choroid cell morphology; and 3) that a mouse strain that develops hydrocephalus shows enhanced phospholemman phosphorylation, increased cell morphology changes, and reductions in Na,K-ATPase. Relevance: A better understanding of these basic mechanisms in the CSF-secreting organ is needed to facilitate new discoveries of ways to reduce CSF secretion, either to replace surgical shunts or to at least stabilize fragile infants prior to surgery. ? ?

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
1R01NS050696-01A2
Application #
7276526
Study Section
Neurotransporters, Receptors, and Calcium Signaling Study Section (NTRC)
Program Officer
Talley, Edmund M
Project Start
2007-08-15
Project End
2011-03-31
Budget Start
2007-08-15
Budget End
2008-03-31
Support Year
1
Fiscal Year
2007
Total Cost
$346,400
Indirect Cost
Name
Massachusetts General Hospital
Department
Type
DUNS #
073130411
City
Boston
State
MA
Country
United States
Zip Code
02199
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