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Modulation of rat brain calpastatin efficiency by post-translational modifications
F Salamino1, M Averna, I Tedesco
1Department of Physiological, Biochemical and Cellular Sciences, University of Sassari, Italy.
FEBS Letters
|August 4, 1997
Summary
Brain calpastatins, calcium-dependent protease inhibitors, exist in two forms. One form
Area of Science:
- Biochemistry
- Molecular Biology
- Neuroscience
Background:
- Calpains are calcium-dependent proteases crucial for cellular processes.
- Calpastatin is the endogenous inhibitor of calpains, regulating their activity.
- Calpastatin exists in multiple forms, with differential activity observed in brain tissue.
Purpose of the Study:
- To investigate the differential activity of brain calpastatin forms against rat brain calpain isozymes.
- To explore the regulatory mechanisms of calpastatin activity, including dephosphorylation and phosphorylation.
Main Methods:
- Purification of calpastatin and calpain isozymes from rat brain.
- Enzymatic assays to determine inhibitory efficiency of calpastatin forms on calpains.
- In vitro phosphorylation and dephosphorylation studies using protein kinase C, protein kinase A, and phosphoprotein phosphatase.
Main Results:
- Two forms of calpastatin were identified in rat brain.
- Only one calpastatin form exhibited high inhibitory activity against rat brain calpain isozymes.
- The second calpastatin form, inactive against homologous calpains, was activated by dephosphorylation.
- Phosphorylation by protein kinase C and A reduced the inhibitory efficiency of the active calpastatin form.
Conclusions:
- Rat brain calpastatin activity is regulated by interconversion between active and inactive forms.
- Dephosphorylation activates calpastatin, while phosphorylation by cAMP- and cGMP-dependent kinases inactivates it.
- These regulatory mechanisms allow for fine-tuning of intracellular calpastatin activity based on cellular needs.