The enzymatic process of A-to-I RNA editing is catalyzed primarily by the adenosine de aminse acting on RNA (ADAR) family proteins that mediates deamination of adenosine to inosine in structured or double-stranded RNAs [ 2].
While there is no doubt that all cells possess plasma membrane adenosine transporters that mediate adenosine uptake and may also allow its release, it is now clear that most of extracellularly-generated adenosine originates from the catabolism of extracellular ATP.
Although cells express carriers that may mediate adenosine translocation into the extracellular milieu, most extracellular adenosine is generated at the expenses of extracellular ATP via extracellular nucleotidases (ecto-ATPases and 5'-nucleotidase) [21], [22].
For example, relevant to the endpoints measured in this study, activation of p42/p44 MAPK has been reported to mediate adenosine-induced nitric oxide production by both calcium-dependent and calcium-insensitive mechanisms [63].
Thus, through catalytic restriction, PAP may produce sufficient amounts of adenosine to mediate antinociception but not enough adenosine to cause overt motor side-effects.
These antinociceptive effects were transiently blocked by the A1R antagonist 8-cyclopentyl-1, 3-dipropylxanthine (CPX), suggesting mPAP dephosphorylates nucleotides to adenosine to mediate antinociception just like human and bovine PAP.
The most common type of known RNA editing in metazoans involves conversion of adenosine to inosine (A-to-I editing) [ 5], which is mediated by adenosine deaminase acting on RNA ADARR) enzymes [ 6- 8].
In this review, we discuss the catalytic mechanisms of MT-A70 domain family proteins for mediating adenosine N6-methylation, the removal of this RNA mark by members of ALKB homologue domain family proteins, and the recognition of these m6A-modified RNAs by YTH domain family proteins.
Numerous investigators have postulated that this adenosine-mediated expression of VEGF might have a role in mediating adenosine-induced angiogenesis ; however, it is still not clear whether adenosine can induce VEGF expression in the intact organism.
In the intestine, the A2B receptor mediates adenosine-induced vectorial chloride secretion (Barrett, 1991; Strohmeier et al., 1995) which, when upregulated, leads to secretory diarrhoea.
