Diadenosine polyphosphates as extracellular signal molecules

Dinucleoside polyphosphates are an interesting group of signalling molecules that control numerous physiological functions. Diadenosine compounds, with a backbone of anything from two to seven phosphates, are known to occur naturally Some of them have been isolated from cerebral nerve terminals and, acting via nucleoside (P1), nucleotide (P2), or dinucleotide receptors, can affect central nervous system function. Many of them have been isolated from human blood platelet secretory granules acid are potentially involved in haemostatic mechanisms and peripheral control of vascular tone. Many visceral organs respond to the application of adenine dinucleotides and, although they act on receptors in the periphery that can be mainly defined as either P1 or P2, evidence is now accumulating for discrete dinucleotide receptors. In the periphery adenine dinucleotides can be potent agonists, with diverse functions, causing contraction or relaxation of smooth muscle. Many P2X receptor proteins and P2Y receptors have been cloned and adenine dinucleotides have a variable pharmacological profile at these receptors and may be useful tools for characterising subtypes of P2X and P2Y receptors. This review provides a broad description of the many extracellular roles of diadenosine polyphosphates as emerging, yet increasingly important, natural ligands for a plethora of structurally diverse mononucleotide and dinucleotide receptors. Drug Dev. Res. 52:260-273, 2001. (C) 2001 Wiley-Liss, Inc.