Modulation of calpastatin specificity in rat tissues by reversible phosphorylation and dephosphorylation.
Two calpastatins, with Mr 110 KD and named calpastatin I and II, have been isolated from rat heart and kidney and displayed distinct inhibitory efficiency with mu- and m-calpain, respectively, as those isolated from rat skeletal muscle. Whereas the level of calpastatin I always exceeds that of mu-calpain, the level of calpastatin II appears to be more closely correlated to the level of m-calpain. As previously shown for skeletal muscle, the two inhibitor proteins can be interconverted by a phosphorylation-dephosphorylation reaction; the enzyme responsible for phosphate incorporation in calpastatin I is now identified in c-AMP dependent protein kinase A. In rat erythrocytes, containing a single calpain form, the single low Mr calpastatin form does not undergo reversible phosphorylation and is equally efficient in respect to typical mu- and m-calpain. The presence of two interconvertible calpastatin forms provides the cells with a highly sensitive mechanism of regulation of the Ca(2+)-dependent proteolytic system.
Salamino
F
F
Institute of Biological Chemistry, University of Genoa, Italy.
De Tullio
R
R
Michetti
M
M
Mengotti
P
P
Melloni
E
E
Pontremoli
S
S
D000818:Animals; D002135:Calcium-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology*; D002154:Calpain / Q000494:pharmacology*; D002846:Chromatography, Affinity; D002848:Chromatography, DEAE-Cellulose; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D015853:Cysteine Proteinase Inhibitors / Q000378:metabolism*; D004912:Erythrocytes / Q000378:metabolism*; D005914:Globins / Q000378:metabolism; D006801:Humans; D007668:Kidney / Q000378:metabolism*; D007700:Kinetics; D009206:Myocardium / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D011494:Protein Kinases / Q000302:isolation & purification / Q000378:metabolism*; D051381:Rats
D002135:Calcium-Binding Proteins; D015853:Cysteine Proteinase Inhibitors; C033668:calpastatin; D005914:Globins; D011494:Protein Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D002154:Calpain