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Biomedical subjects

J F Kuo

Publications and source records attributed to J F Kuo.

At least 163 records · Page 9Linked to original sources
PubMed1975

Divergent actions of protein kinase modulator in regulating mammalian cyclic GMP-dependent and cyclic AMP-dependent protein kinases.

Protein kinase modulator can either augment or depress phosphorylation of substrate proteins catalyzed by cyclic GMP-dependent and cyclic AMP-dependent protein kinases prepared from mammalian and arthropod tissues. Alteration by the modulator of the phosphorylating activity of the protein kinases is considered to be due to modification of protein substrate specificity subsequent to interaction of the modulator with the catalytic subunits of the enzymes. It is likely that the physiologic role of the modulator is to monitor the opposing effects of cyclic GMP and cyclic AMP by regulating the activity of respective protein kinases. Thus the modulator may function as a biologic "fine tuner" providing on additional mechanism by which the signals imparted to cells by physiologic stimuli can be correctly expressed.

Animals↗
PubMed1975

Changes in relative levels of guanosine-3':5'-monophosphate-dependent and adenosine-3':5'-monophosphate-dependent protein kinases in lung, heart, and brain of developing guinea pigs.

Canges in relative levels of protein kinases (ATP:protein phosphotransferase, EC 2.7.1.37) stimulated by either guanosine 3':5'-monophosphate (cyclic-GMP) or adenosine 3':5'-monophosphate (cyclic-AMP) were examined in extracts of the lung, heart, brain, and liver from guinea pigs at various stages of development. The level of cyclic-GMP-dependent protein kinase in the fetal lung, which was found to be the highest of any mammalian tissue samples examined, declined during development. On the other hand, the level of cyclic-AMP-dependent protein kinase in the same extracts, which was initially lower than that of the cyclic-GMP-dependent enzyme, increased during development and reached a level higher than that of the cyclic-GMP-dependent enzyme when the animals reached maturity. This reciprocal change in level of the two classes of protein kinases in developing lung was demonstrated further by chromatographing the extracts on Sephadex G-200 and quantitating the activity of the isolated enzymes. A decrease in the ratio of the two classes of protein kinases qualitatively similar to that seen in the lung was also noted in the developing heart. An increase in the ratio of the enzymes, however, was seen in the developing brain. Unlike in the lung, heart, and brain, no change in relative level and ratio of the enzymes was noted in liver during development. These results suggest that a balance between the effects of cyclic-GMP-dependent and cyclic-AMP-dependent protein kinases may be important in normal development of certain tissues.

Animals↗
PubMed1974

Guanosine 3':5'-monophosphate-dependent protein kinases in mammalian tissues.

The mammalian protein kinase activity stimulated preferentially by low concentrations of guanosine 3':5'-monophosphate (cyclic GMP), but not by adenosine 3':5'-monophosphate (cyclic AMP), was readily assayed in a modified incubation system that contained a neutral phosphate buffer, protein kinase modulator, and arginine-rich histone. Cyclic GMP-dependent protein kinase activity assayed under these conditions was about two to three orders of magnitude higher than that previously detected. The enzyme activity occurred in all guinea pig and rat tissues (lung, heart, aorta, brain, liver, ileum, adipose, and pancreatic islets) examined. The activity can be separated from the cyclic AMP-dependent protein kinase activity, also present in the same tissues, by means of either Sephadex G-200 gel filtration or ammonium sulfate fractionation. The cyclic GMP-dependent enzyme preparations had K(a) values for cyclic GMP ranging from 0.03 to 0.12 muM, compared to the K(a) values for cyclic AMP ranging from 0.6 to 3.8 muM. The presence of phosphate and protein kinase modulator was essential for maximal cyclic GMP-dependent enzyme activity. The occurrence of high levels of cyclic GMP-dependent protein kinase activity in mammalian tissues clearly suggests that it may serve as a "target" enzyme for cyclic GMP, mediating many biological effects of this cyclic nucleotide.

Adenosine Triphosphate↗
PubMed1972

Role of muscarinic cholinergic receptors in regulation of guanosine 3':5'-cyclic monophosphate content in mammalian brain, heart muscle, and intestinal smooth muscle.

Effects of acetylcholine and of agents that mimic or block its physiological actions have been studied upon concentrations of guanosine 3':5'-cyclic monophosphate (cyclic GMP) and adenosine 3':5'-cyclic monophosphate (cyclic AMP) in slices of mammalian cerebral cortex, heart ventricle, and ileum. Acetylcholine, and cholinomimetic agents with a predominantly muscarinic action, such as methacholine, bethanechol, and pilocarpine, induced an increase in the concentration of cyclic GMP, accompanied by no change or a slight decrease in the concentration of cyclic AMP, in all three tissues studied. Tetramethylammonium, a cholinomimetic agent with a predominantly nicotinic action, on the other hand, did not significantly alter concentrations of either cyclic GMP or cyclic AMP. The increase in the tissue content of cyclic GMP induced by acetylcholine and its muscarinic analogs was antagonized by atropine, a muscarinic blocking agent, but not by hexamethonium, a nicotinic blocking agent. These and other results suggest the generalization that the interaction of acetylcholine with muscarinic receptors, but not with nicotinic receptors, causes an increase in the concentration of cyclic GMP. The data are compatible with the hypothesis that cyclic GMP may mediate the muscarinic actions of acetylcholine. The antagonistic actions of cholinergic and adrenergic agents on the physiology of contraction of intestinal smooth muscle and of cardiac muscle are reflected in, and may result from, antagonistic actions of these compounds on the levels of both cyclic GMP and cyclic AMP in these tissues.

Acetylcholine↗