Suppressive effect of regucalcin on protein phosphatase activity in the heart cytosol of normal and regucalcin transgenic rats. 2004

Emiko Ichikawa, and Yoshinori Tsurusaki, and Masayoshi Yamaguchi
Laboratory of Endocrinology and Molecular Metabolism, Graduate School of Nutritional Sciences, University of Shizuoka, Shizuoka 422-8526, Japan.

The role of regucalcin, a regulatory protein in intracellular signaling pathway, in the regulation of protein phosphatase activity in the heart muscle cytosol was investigated by using normal (wild-type) and regucalcin transgenic (TG) rats. Protein phosphatase activity was assayed in a reaction mixture containing the cytosolic protein in the presence of phosphotyrosine, phosphoserine, and phosphothreonine. The addition of calcium chloride (10 and 20 microM) in the enzyme reaction mixture caused a significant increase in protein phosphatase activity toward three phosphoaminoacids. Trifluoperazine (10 and 20 microM), an antagonist of calmodulin, completely inhibited calcium (10 microM) addition-increased protein phosphatase activity toward three phosphoaminoacids. Moreover, the calcium (10 microM)-increased enzyme activity toward phosphoserine and phosphothreonine was significantly enhanced by the addition of calmodulin (2.5 or 5 microg/ml). Such an enhancement was not seen in the presence of phosphotyrosine. Regucalcin (10(-9) and 10(-8) M) significantly inhibited protein phosphatase activity toward three phosphoaminoacids in the presence of ethylene glycol bis (2-aminoethlether) N,N,N',N'-tetraacetic acid (EGTA; 1 mM), without Ca2+ addition. The inhibitory effect of regucalcin (10(-10)-10(-8) M) was also seen in the presence of calcium chloride (10 microM). Western blot analysis showed a remarkable expression of regucalcin protein in the cytosol of heart of regucalcin TG female rats as compared with that of wild-type female rats. Protein phosphatase activity toward three phosphoaminoacids was significantly decreased in the heart cytosol of TG rats. The enhancing effect of calcium (10 microM) addition on protein phosphatase activity toward three phosphoaminoacids was not seen in the heart cytosol of TG rats. This study demonstrates that endogenous regucalcin plays a suppressive role in the regulation of protein phosphatase activity in rat heart cytoplasm.

UI MeSH Term Description Entries
D009206 Myocardium The muscle tissue of the HEART. It is composed of striated, involuntary muscle cells (MYOCYTES, CARDIAC) connected to form the contractile pump to generate blood flow. Muscle, Cardiac,Muscle, Heart,Cardiac Muscle,Myocardia,Cardiac Muscles,Heart Muscle,Heart Muscles,Muscles, Cardiac,Muscles, Heart
D010749 Phosphoprotein Phosphatases A group of enzymes removing the SERINE- or THREONINE-bound phosphate groups from a wide range of phosphoproteins, including a number of enzymes which have been phosphorylated under the action of a kinase. (Enzyme Nomenclature, 1992) Phosphoprotein Phosphatase,Phosphoprotein Phosphohydrolase,Protein Phosphatase,Protein Phosphatases,Casein Phosphatase,Ecto-Phosphoprotein Phosphatase,Nuclear Protein Phosphatase,Phosphohistone Phosphatase,Phosphoprotein Phosphatase-2C,Phosphoseryl-Protein Phosphatase,Protein Phosphatase C,Protein Phosphatase C-I,Protein Phosphatase C-II,Protein Phosphatase H-II,Protein-Serine-Threonine Phosphatase,Protein-Threonine Phosphatase,Serine-Threonine Phosphatase,Threonine Phosphatase,Ecto Phosphoprotein Phosphatase,Phosphatase C, Protein,Phosphatase C-I, Protein,Phosphatase C-II, Protein,Phosphatase H-II, Protein,Phosphatase, Casein,Phosphatase, Ecto-Phosphoprotein,Phosphatase, Nuclear Protein,Phosphatase, Phosphohistone,Phosphatase, Phosphoprotein,Phosphatase, Phosphoseryl-Protein,Phosphatase, Protein,Phosphatase, Protein-Serine-Threonine,Phosphatase, Protein-Threonine,Phosphatase, Serine-Threonine,Phosphatase, Threonine,Phosphatase-2C, Phosphoprotein,Phosphatases, Phosphoprotein,Phosphatases, Protein,Phosphohydrolase, Phosphoprotein,Phosphoprotein Phosphatase 2C,Phosphoseryl Protein Phosphatase,Protein Phosphatase C I,Protein Phosphatase C II,Protein Phosphatase H II,Protein Phosphatase, Nuclear,Protein Serine Threonine Phosphatase,Protein Threonine Phosphatase,Serine Threonine Phosphatase
D002118 Calcium A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes. Coagulation Factor IV,Factor IV,Blood Coagulation Factor IV,Calcium-40,Calcium 40,Factor IV, Coagulation
D002122 Calcium Chloride A salt used to replenish calcium levels, as an acid-producing diuretic, and as an antidote for magnesium poisoning. Calcium Chloride Dihydrate,Calcium Chloride, Anhydrous
D002135 Calcium-Binding Proteins Proteins to which calcium ions are bound. They can act as transport proteins, regulator proteins, or activator proteins. They typically contain EF HAND MOTIFS. Calcium Binding Protein,Calcium-Binding Protein,Calcium Binding Proteins,Binding Protein, Calcium,Binding Proteins, Calcium,Protein, Calcium Binding,Protein, Calcium-Binding
D002147 Calmodulin A heat-stable, low-molecular-weight activator protein found mainly in the brain and heart. The binding of calcium ions to this protein allows this protein to bind to cyclic nucleotide phosphodiesterases and to adenyl cyclase with subsequent activation. Thereby this protein modulates cyclic AMP and cyclic GMP levels. Calcium-Dependent Activator Protein,Calcium-Dependent Regulator,Bovine Activator Protein,Cyclic AMP-Phosphodiesterase Activator,Phosphodiesterase Activating Factor,Phosphodiesterase Activator Protein,Phosphodiesterase Protein Activator,Regulator, Calcium-Dependent,AMP-Phosphodiesterase Activator, Cyclic,Activating Factor, Phosphodiesterase,Activator Protein, Bovine,Activator Protein, Calcium-Dependent,Activator Protein, Phosphodiesterase,Activator, Cyclic AMP-Phosphodiesterase,Activator, Phosphodiesterase Protein,Calcium Dependent Activator Protein,Calcium Dependent Regulator,Cyclic AMP Phosphodiesterase Activator,Factor, Phosphodiesterase Activating,Protein Activator, Phosphodiesterase,Protein, Bovine Activator,Protein, Calcium-Dependent Activator,Protein, Phosphodiesterase Activator,Regulator, Calcium Dependent
D002265 Carboxylic Ester Hydrolases Enzymes which catalyze the hydrolysis of carboxylic acid esters with the formation of an alcohol and a carboxylic acid anion. Carboxylesterases,Ester Hydrolases, Carboxylic,Hydrolases, Carboxylic Ester
D003600 Cytosol Intracellular fluid from the cytoplasm after removal of ORGANELLES and other insoluble cytoplasmic components. Cytosols
D005260 Female Females
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia

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