Cyclic nucleotide system

Before discussing effects of the retinoids on the cyclic nucleotide/calcium-dependent regulatory systems, it is necessary to identify the various components of these systems. The cyclic nucleotide system contains many elements (1) the substrate ATP (or GTP) (2) the synthetic and degradative enzymes adenylate or... 

B. Co-factor Control Since several enzymes with varying co-factor requirements are involved in the cyclic nucleotide system, it is at least theoretically possible to modulate the system significantly by controlling the availablilty of the essential co-factors. Of these factors, Ca++ occupies a commanding position. Ca++ generally inhibits AC activity, is essential for GC activity, modulates PDE activity and its efflux appears to be controlled by the prostaglandins . Furthermore, activation of protein kinase by cyclic AMP seems to enhance Ca++ upteike . The in r-tance of Ca++ to the functioning of cyclic nucleotide system is indicated by the lack of hormonal response in Ca++-free media in many systems in spite of an observed accumulation of the cyclic nucleotides. 

B. The Membrane Receptor-Adenylate Cyclase-cAMP-Cyclic Nucleotide Systems... 

Waisman, D. M., Singh, T. J., and Wang, J. H., 1978, The modulator-dependent protein kinase. A multifunctional protein kinase activatable by the Ca -dependent modulator protein of the cyclic nucleotide system, /. Biol. Chem. 253 3387. 

Calmodulin and cyclic nucleotide-dependent second messenger systems... 

G PROTEINS 335 PHOSPHOINOSITIDES 347 CYCLIC NUCLEOTIDES IN THE NERVOUS SYSTEM 361... 

Although tremendous progress has been made in characterizing the enzymes that control the synthesis and metabolism of cyclic nucleotides in the nervous system, our understanding of the regulation and interaction of these systems is far from complete. Work is now needed to definitively characterize, for each of these enzyme sub-types, its unique distribution pattern in the brain as well as its distinct functional and regulatory properties. 

Repaske, D., Corbin, J. G., Conti, M. and Goy, M. F. A cyclic GMP-stimulated cyclic nucleotide phosphodiesterase gene is highly expressed in the limbic system of the rat brain. Neuroscience 56 673-686,1993. 

Karbon, E. W. and Enna, S. J. (1985) Characterization of the relationship between gamma-aminobutyric acid B agonists and transmitter-coupled cyclic nucleotide-generating systems in rat brain. Mol. Pharmacol. 27,53-59. 

Katz, A. M., Tada, M., and Kirchberger, M. A. (1975) Control of calcium transport in the myocardium by the cyclic AMP-protein kinase system. In Advances in Cyclic Nucleotide Research, Vol. 5, edited by G. 1. Drummond, P. Greengard, and G. A. Robinson, pp. 453-472. Raven Press, New York. 

Ferrendelli, J. A. (1978). Distribution and regulation of cyclic GMP in the central nervous system. Adv. Cyclic Nucleotide Res. 9, 453-464. 

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