Non Canonical Cyclic Nucleotides

The cyclic purine nucleotides 3’,5’-cAMP and 3’,5’-cGMP are well-established second messengers. cGMP has recently been covered in a volume of the Handbook of Experimental Pharmacology (volume 191). In addition to 3’,5’-cAMP and 3’,5’-cGMP, so-called non-canonical cyclic nucleotides exist. These comprise the cyclic pyrimidine nucleotides 3’,5’-cCMP and 3’,5’-cUMP, the purine nucleotide 3’,5’-cIMP, the 2’,3’-nucleoside monophosphates and cyclic dinucleotides. In this volume of the Handbook of Pharmacology, word-leading experts in the field summarize our current knowledge on these non-canonical cyclic nucleotides, discuss open questions, future research directions and the pharmacotherapeutic implications. Special emphasis will be given to the emerging roles of 3’,5’-cCMP and 3’,5’-cUMP as second messengers with regard to generators, effectors, biological functions, inactivation and bacterial toxins. The role of 3’,5’-cIMP as potential second messenger will also be critically discussed. Furthermore, we will consider transport of cyclic nucleotides and their potential role as first messengers. The role of the cyclic dinucleotide cGAMP in the immune system will covered, too. Lastly, the book will present important methodological aspects ranging from mass-spectrometric methods for cyclic nucleotide detection to the synthesis of nucleotide analogs as experimental tools and holistic methods for analysis of cyclic nucleotide effects.

The purpose of the present volume, the first of two on the pharmacology, biochemistry, and physiology of cyclic nucleotides, is to provide a comprehensive and up-to-date anthology on the nature and role of these important chemical regulators. Each of the chapters is the work of internationally known researchers who present a lucid and detailed review of their subject and not merely a single laboratory's viewpoint. The chapters emphasize critical assessments of the field rather than mere listings of experimental findings. By so doing, the contributors present the role of cyclic nucleotides in relationship to other intracellular regulators. Each chapter begins with a detailed summary to allow the reader to obtain a rapid overview of subsequent material. In addition, there are extensive bibliographies and a detailed subject index. Wherever pertinent, the chapters contain sections on drug mechanisms, physiological relevance, and disease processes. The Volume is divided into two sections, each beginning with an overview written by Professors T. W. RALL and P. GREENGARD, respectively. The first section focuses on the detailed pharmacology and chemistry of cyclic nucleotides, including their formation, degradation, measurement, and interaction with various modulatory agents, such as receptors and calcium. The second section is concerned with the biochemistry of protein phosphorylation, a process which appears to be one of the most important mechanisms for the intracellular expression of cyclic nucleotide action in eukaryotic cells.

Cyclic nucleotides are intimately involved in the consequences of either stimulation or blockade of receptors; therefore, an understanding of the biochemistry of cyclic nucleotides ought to be important for pharmacologists. Pharmacology is a science that among other things investigates chemical compounds that affect the physiology of cells, tissues and organs. Frequently pharmacologists account for the effect of low concentrations of a drug upon a tissue by invoking the presence of a receptor upon the surface of the cell. Traditional pharmacologists excelled at identifying and classifying the properties of receptors. A. J. CLARK'S monograph in the earlier series of the Handbook of Experimental Pharmacology (CLARK 1937) summarized the mathematics underlying the traditional pharmacological approach towards receptors. By its nature, however, classic pharmacology provided little useful information about the intracellular events occurring as a consequence of occupying a receptor; for example, ALQUIST (1948) identified the beta-adrenocep tor, but he did not provide any insight into how stimulation of the receptor produces tissue-specific physiological responses. The discovery of cyclic AMP by RALL and SUTHERLAND (see RALL, Vol. I) led to biochemical investigations of many different receptors (including ALQUIST'S beta-adrenoceptor) that share a cyclic nucleotide as a common factor in the biochemical mechanisms that translate the occupancy of receptors into physiological effects. Ten years ago, in the introduction to their monograph on cyclic nucleotides, ROBISON et al. (1971) commented on the rapid growth of interest in cyclic nucleotides over the preceding years.