title: Orthovanadate stimulates cyclic guanosine monophosphate-inhibited cyclic adenosine monophosphate phosphodiesterase activity in isolated rat fat pads through activation of particulate myelin basic protein kinase by protein tyrosine kinase.
abstract: Involvement of protein kinases in the stimulation of cGMP-inhibited cAMP phosphodiesterase (PDE) activity by orthovanadate (vanadate) was studied. When the fat pads were incubated with 2 mM vanadate or 10 nM insulin, the stimulation of myelin basic protein kinase (MBPK) activity in the particulate by vanadate reached a maximum at 60 min. In contrast, insulin showed a transient increase at 20 min. A 60-min incubation of the fat pads with vanadate stimulated all activities of protein tyrosine kinase (PTK), MBPK, and PDE in the particulate, in a similar dose-dependent manner. Amiloride, a PTK inhibitor, inhibited the stimulations of three enzymes by vanadate in a similar concentration range. Enzyme fractions, which were separated from the solubilized particulate, were subjected to the immunoblot analysis. A fraction of MBPK was identified to contain a major protein of mol wt (44K) and a minor one (42K), both of which are immunoreactive with a mitogen-activated protein kinase (MAPK) antibody. The partially purified PDE activity was stimulated by the addition of the partially purified MBPK. The further stimulation was observed with the PTK-activated MBPK. These results suggest that vanadate stimulates in part the PDE activity through the activation of the particulate MBPK, probably MAPKs, by PTK sensitive to vanadate.
authors.affiliation: Department of Biochemistry, Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, Hiroshima, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Ueki
authors.forename: S
authors.initials: S
authors.lastname: Mitsugi
authors.forename: Y
authors.initials: Y
authors.lastname: Kawashima
authors.forename: T
authors.initials: T
authors.lastname: Motoyashiki
authors.forename: T
authors.initials: T
authors.lastname: Morita
mesh_terms: D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000302:isolation & purification / Q000378:metabolism*; D000273:Adipose Tissue / Q000201:enzymology*; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000302:isolation & purification / Q000378:metabolism*; D006152:Cyclic GMP / Q000494:pharmacology*; D004789:Enzyme Activation; D005459:Fluorides / Q000494:pharmacology; D005994:Glycerophosphates / Q000494:pharmacology; D038362:Glycogen Synthase Kinase 3; D008297:Male; D008954:Models, Biological; D017680:Potassium Compounds / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000302:isolation & purification / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D014638:Vanadates / Q000494:pharmacology*
chemical_list: D005994:Glycerophosphates; D017680:Potassium Compounds; D014638:Vanadates; C033320:potassium fluoride; D011505:Protein-Tyrosine Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D038362:Glycogen Synthase Kinase 3; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D006152:Cyclic GMP; D005459:Fluorides; C031463:beta-glycerophosphoric acid