Recent progress in the study of the intracellular functions of diadenosine polyphosphates

Abstract

Recent developments in the effort to understand the metabolism and function of the intracellular dinucleoside polyphosphates were described by nine speakers from some of the world's leading laboratories in this field in a workshop at the Purines 2000 International Symposium on Nucleosides and Nucleotides held in Madrid in July, 2000. Topics were wide-ranging and included phenotypic analyses of yeast mutants defective in enzymes of dinucleoside polyphosphate degradation, virally encoded catabolic enzymes, the structure and function of the Fhit tumor suppressor and Fhit-nitrilase fusion proteins and the relationship of Fhit to human diadenosine triphosphate hydrolase, site-directed mutagenesis of diadenosine tetraphosphate hydrolase, novel nucleotide analogs for studying hydrolase function, the synthesis of dinucleoside polyphosphates by ligases, and the possible roles of diadenosine tri-and tetraphosphates in insulin function and of diadenosine tetraphosphate in the heat-shock response of Escherichia coli. The results presented and the ensuing discussions showed that, while considerable progress is being made in the field, it still has the capacity to tease and frustrate and produce the unexpected result. Drug Dev. Res. 52:249-259, 2001.

The Nudix hydrolase superfamily

“…An exception is Thermus thermophilus Ndx1, which strongly prefers Ap 6 A and is more similar to animal Ap 4 A hydrolases and the DIPP family [42]. Ap 4 A is synthesised by aminoacyl-tRNA synthetases and other AMP-forming ligases [43] and may have a number of roles in prokaryotes, including modulating chaperone and heat shock protein activity [44,45] and controlling the timing of cell division [46]. If allowed to accumulate unchecked, it could also interfere with a number of ATP-dependent reactions [47].…”

Regulation of Dinucleoside Polyphosphate Pools by the YgdP and ApaH Hydrolases Is Essential for the Ability of Salmonella enterica serovar Typhimurium to Invade Cultured Mammalian Cells

“…The most widely studied are diadenosine 5Ј,5ٞ-P 1 ,P 3 -triphosphate (Ap 3 A) and diadenosine 5Ј,5ٞ-P 1 ,P 4 -tetraphosphate (Ap 4 A), for which several functions have been suggested, although none yet conclusively proved (1)(2)(3). In Escherichia coli, Ap 4 A has been proposed to couple DNA replication to cell division (4,5) and to participate in stress responses by modulating protein refolding by chaperones (3,6,7).…”

Synthesis of dinucleoside tetraphosphates in transfected cells by a firefly luciferase reporter gene

“…Ap 4 A has in the past been linked to the regulation of DNA replication and repair and to the modulation of stress responses, although none of these has been fully substantiated in mammalian cells [10,11]. More recently, intracellular Ap 3 A and Ap 4 A have been shown to mediate the glucose-induced blockade of the pancreatic b cell ATP-regulated potassium channel [24,25], while addition of Ap 4 A at 10 mM to certain reversibly permeabilised cells has been reported to induce cell cycle arrest and apoptosis [26].…”

“…In vitro, firefly luciferase can synthesise dinucleoside polyphosphates, predominantly those containing at least one adenine moiety and four or more phosphate groups, such as diadenosine 5¢,5¢¢¢-P 1 ,P 4 -tetraphosphate (Ap 4 A) and adenosine(5¢)tetraphospho(5¢)guanosine (Ap 4 G) [7,8]. These compounds have been ascribed various intracellular signalling roles and are potentially toxic if allowed to accumulate [9][10][11]. In a mechanism analogous to that used by aminoacyl-tRNA synthetases, the enzymes believed to be the predominant source of Ap 4 A in vivo, D-luciferin acts as an adenylate acceptor from ATP, forming luciferyl-AMP then dehydroluciferyl-AMP as intermediates, the latter then donating the AMP moiety to another ATP to yield Ap 4 A [7,12].…”