Identification of Soluble Protein Phosphatases That Dephosphorylate Voltage-sensitive Sodium Channels in Rat Brain
| Autor: | Sandra Rossie, Tzu-chin Chen, Tamara P. Kondratyuk, Brian K. Law |
|---|---|
| Rok vydání: | 1995 |
| Předmět: |
Calmodulin
Blotting Western Phosphatase Biochemistry Chromatography Affinity Chromatography DEAE-Cellulose Sodium Channels Calcium Chloride chemistry.chemical_compound Cytosol Ethers Cyclic Okadaic Acid Phosphoprotein Phosphatases Animals Protein Phosphatase 2 Muscle Skeletal Molecular Biology Sodium channel activity biology Myocardium Sodium channel Acid phosphatase Brain Cell Biology Protein phosphatase 2 Okadaic acid Cyclic AMP-Dependent Protein Kinases Molecular biology Rats Molecular Weight Kinetics chemistry Chromatography Gel biology.protein Phosphorylation Cattle Electrophoresis Polyacrylamide Gel Rabbits |
| Zdroj: | Journal of Biological Chemistry. 270:7750-7756 |
| ISSN: | 0021-9258 |
| DOI: | 10.1074/jbc.270.13.7750 |
| Popis: | Rat brain sodium channels are phosphorylated at multiple serine residues by cAMP-dependent protein kinase. We have identified soluble rat brain phosphatases that dephosphorylate purified sodium channels. Five separable forms of sodium channel phosphatase activity were observed. Three forms (two, approximately 234 kDa and one, 192 kDa) are identical or related to phosphatase 2A, since they were 85-100% inhibited by 10 nM okadaic acid and contained a 36-kDa polypeptide recognized by a monoclonal antibody directed against the catalytic subunit of phosphatase 2A. Immunoblots performed using antibodies specific for isoforms of the B subunit of phosphatase 2A indicate that the two major peaks of phosphatase 2A-like activity, A1 and B1, are enriched in either B' or B alpha. The remaining two activities (approximately 100 kDa each) probably represent calcineurin. Each was relatively insensitive to okadaic acid, was active only in the presence of CaCl2 and calmodulin, and contained a 19-kDa polypeptide recognized by a monoclonal antibody raised against the B subunit of calcinerurin. Treatment of synaptosomes with okadaic acid to inhibit phosphatase 2A or cyclosporin A to inhibit calcineurin increased apparent phosphorylation of sodium channels at cAMP-dependent phosphorylation sites, as assayed by back phosphorylation. These results indicate that phosphatase 2A and calcineurin dephosphorylate sodium channels in brain, and thus may counteract the effect of cAMP-dependent phosphorylation on sodium channel activity. |
| Databáze: | OpenAIRE |
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