Protein phosphatase-1 and -2A, kinase FA, and casein kinase II in skeletal muscle of streptozotocin diabetic rats.
Protein phosphatase-1 (PP-1) and -2A (PP-2A), two regulatory subunits of PP-1, the glycogen-binding subunit G and inhibitor-2 (I-2), kinase FA, and casein kinase II (CK-II) were investigated in skeletal muscle of diabetic rats 2 days after streptozotocin injection. FA and CK-II activate PP-1 in vitro and might be involved in the activation of PP-1 by insulin. Following muscle fractionation we found that (1) diabetes decreased both basal and trypsin-stimulated PP-1 activities; the decrease was more significant in the glycogen-bound and microsomal fractions than in the cytosol (cytosolic PP-1 decreased as specific activity but not as activity/g of muscle); also PP-2A was lower in diabetic cytosols; (2) less G was immunoprecipitated from diabetic glycogen-bound fractions compared to controls, while I-2 was not significantly changed; (3) diabetes decreased also FA (assayed as PP-1 activator) and CK-II (assayed using a synthetic peptide as substrate); (4) diabetes did not have any effect on phosphorylase (a + b) activity in the glycogen-bound fraction. Altogether the data show that acute diabetes decreased PP-1, one of its regulatory subunits and two potentially physiological regulators of PP-1, in addition to PP-2A. This may indicate that insulin is responsible for the long-term regulation of the same enzymes that are also under acute insulin control.
Metallo
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Dipartimento di Biomedicina Sperimentale, Università di Pisa, Italy.
Villa-Moruzzi
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D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D047388:Casein Kinases; D003600:Cytosol / Q000201:enzymology; D003921:Diabetes Mellitus, Experimental / Q000201:enzymology*; D005260:Female; D009132:Muscles / Q000201:enzymology*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D054645:Protein Phosphatase 1; D051381:Rats; D011919:Rats, Inbred Strains
D011494:Protein Kinases; D047388:Casein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1