Protein kinase C and calmodulin effects on the plasma membrane Ca2+-ATPase from excitable and nonexcitable cells.
Mol Cell Biochem
; 173(1-2): 79-87, 1997 Aug.
Article
in En
| MEDLINE
| ID: mdl-9278257
ABSTRACT
We have purified Ca2+-ATPase from synaptosomal membranes (SM)1 from rat cerebellum by calmodulin affinity chromatography. The enzyme was identified as plasma membrane Ca2+-ATPase by its interaction with calmodulin and monoclonal antibodies produced against red blood cell (RBC) Ca2+-ATPase, and by thapsigargin insensitivity. The purpose of the study was to establish whether two regulators of the RBC Ca2+-ATPase, calmodulin and protein kinase C (PKC), affect the Ca2+-ATPase isolated from excitable cells and whether their effects are comparable to those on the RBC Ca2+-ATPase. We found that calmodulin and PKC activated both enzymes. There were significant quantitative differences in the phosphorylation and activation of the SM versus RBC Ca2+-ATPase. The steady-state Ca2+-ATPase activity of SM Ca2+-ATPase was approximately 3 fold lower and significantly less stimulated by calmodulin. The initial rate of PKC catalyzed phosphorylation (in the presence of 12-myristate 13-acetate phorbol) was approximately two times slower for SM enzyme. While phosphorylation of RBC Ca2+-ATPase approached maximum level at around 5 min, comparable level of phosphorylation of SM Ca2+-ATPase was observed only after 30 min. The PKC-catalyzed phosphorylation resulted in a statistically significant increase in Ca2+-ATPase activity of up to 20-40%, higher in the SM Ca2+-ATPase. The differences may be associated with diversities in Ca2+-ATPase function in erythrocytes and neuronal cells and different isoforms composition.
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Collection:
01-internacional
Database:
MEDLINE
Main subject:
Protein Kinase C
/
Calmodulin
/
Cell Membrane
/
Calcium-Transporting ATPases
/
Erythrocytes
/
Neurons
Type of study:
Prognostic_studies
Limits:
Animals
Language:
En
Journal:
Mol Cell Biochem
Year:
1997
Document type:
Article
Affiliation country:
United States