Protein tyrosine phosphorylation in cardiovascular system |
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Authors: | Srivastava Ashok K |
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Institution: | (1) Department of Oral Biology JH Miller Health Science Center, University of Florida, P.O. Box 100424, 32610 Gainesville, FL, USA;(2) Department of Pharmacology and Experimental Therapeutics, University of Florida, 32610 Gainesville, FL, USA |
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Abstract: | Treatment of rat parotid acinar cells with sodium orthovanadate (an inhibitor of protein tyrosine phosphatase) caused a dose-dependent inhibition of phosphatase activity as measured by the hydrolysis of para nitrophenylphosphate (pNPP). Inclusion of 50 M sodium orthovanadate inin vitro gland cultures prevented the amylase secretion from both untreated control and isoproterenol-stimulated parotid acinar cells. Four different tyrosine-phosphorylated proteins with Mr 40, 45, 70 and 95 kDa, respectively, were identified in secretory granule preparations from rat parotid glands by immunoblot using a monospecific antibody for phosphotyrosine. An increase in the phosphorylation levels of these phosphoproteins was noted in the presence of 50 M sodium orthovanadate, suggesting that a protein tyrosine phosphatase (PTPase) is involved in parotid gland protein dephosphorylation reactions. Using antibody to Syp (a PTPase belonging to class 1D), a major fraction of subcellular activity was found to be associated with secretory granule membranes. These results suggest the possible involvement of a PTPase (Syp) in parotid gland secretory mechanisms. |
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Keywords: | secretion dephosphorylation signal transduction phosphotyrosine |
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