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Cl(-)-ATPase in rat brain and kidney.
C Inagaki1, N Hattori, K Kitagawa
1Department of Pharmacology, Kansai Medical University, Fumizono-cho 10-15, Moriguchi-City, Osaka 570-8506, Japan. inagaki@takii.kmu.ac.jp
The Journal of Experimental Zoology
|March 10, 2001
Summary
The study identified a chloride-stimulated ATPase (Cl(-)-ATPase/pump) as an active chloride transporter in brain neurons. This transporter
Area of Science:
- Neuroscience
- Cell Biology
- Biochemistry
Background:
- Chloride ion (Cl(-)) transport is crucial for neuronal function.
- An active, outwardly directed Cl(-) transporter in brain neurons remains to be fully characterized.
- The Cl(-)-stimulated ATPase/ATP-dependent Cl(-) pump (Cl(-)-ATPase/pump) is a candidate for this transporter.
Purpose of the Study:
- To isolate and characterize the Cl(-)-ATPase/pump from rat brain.
- To investigate the role of phosphatidylinositol-4-monophosphate in Cl(-)-ATPase/pump activity.
- To explore the potential involvement of Cl(-)-ATPase/pump in Alzheimer's disease (AD).
Main Methods:
- Isolation of a 520-kDa protein complex with Cl(-)-ATPase/pump activity from rat brain.
- Characterization of the complex's four protein subunits, including a 51-kDa phosphorylenzyme subunit.
- Inhibition studies using an antiserum against the 51-kDa protein.
- Enzyme histochemistry and immunohistochemistry to localize Cl(-)-ATPase activity/immunoreactivity.
- Reconstitution experiments in liposomes and studies using LiCl (inositolphosphatase inhibitor) in cultured neurons.
- Analysis of Cl(-)-ATPase activity in brains of Alzheimer's disease patients.
Main Results:
- A four-subunit (51, 55, 60, 62 kDa) protein complex with Cl(-)-ATPase/pump activity was isolated.
- The 51-kDa subunit is a covalent phosphorylenzyme; antiserum against it inhibited activity.
- Cl(-)-ATPase-like activity/immunoreactivity was found on neuronal plasma membranes and renal basolateral membranes.
- Activity was highest in liposomes with phosphatidylinositol-4-monophosphate and inhibited by LiCl.
- Reduced Cl(-)-ATPase activity was observed in Alzheimer's disease brains.
Conclusions:
- Cl(-)-ATPase is an outwardly directed ATP-dependent Cl(-) transporter composed of four subunits.
- Phosphatidylinositol-4-monophosphate regulates Cl(-)-ATPase/pump activity.
- Altered Cl(-)-ATPase activity may contribute to the pathophysiology of neurodegenerative diseases like Alzheimer's.