A membrane network of receptors and enzymes for adenine nucleotides and nucleosides

Abstract

Most cells express more than one receptor plus degrading enzymes for adenine nucleotides or nucleosides, and cellular responses to purines are rarely compatible with the actions of single receptors. Therefore, these receptors are viewed as components of a combinatorial receptor web rather than self-dependent entities, but it remained unclear to what extent they can associate with each other to form signalling units. P2Y(1), P2Y(2), P2Y(12), P2Y(13), P2X(2), A(1), A(2A) receptors and NTPDase1 and -2 were expressed as fluorescent fusion proteins which were targeted to membranes and signalled like the unlabelled counterparts. When tested by FRET microscopy, all the G protein-coupled receptors proved able to form heterooligomers with each other, and P2Y(1), P2Y(12), P2Y(13), A(1), A(2A), and P2X(2) receptors also formed homooligomers. P2Y receptors did not associate with P2X, but G protein-coupled receptors formed heterooligomers with NTPDase1, but not NTPDase2. The specificity of prototypic interactions (P2Y(1)/P2Y(1), A(2A)/P2Y(1), A(2A)/P2Y(12)) was corroborated by FRET competition or co-immunoprecipitation. These results demonstrate that G protein-coupled purine receptors associate with each other and with NTPDase1 in a highly promiscuous manner. Thus, purinergic signalling is not only determined by the expression of receptors and enzymes but also by their direct interaction within a previously unrecognized multifarious membrane network.

Cellular function and molecular structure of ecto-nucleotidases

“…In addition to homooligomers, NTPDases may also form heterooligomers and engage in complexes with purine receptors. Using FRET microscopy of heterologously expressed fluorescence-tagged proteins, close molecular interaction, indicating complex formation, was observed between rat NTPDase1 and NTPDase2 and between NTPDase1 and a variety of P2Y nucleotide and P1 adenosine receptors [164]. The close interaction between NTPDases and P2Y receptors would have a severe impact on the availability of nucleotide agonists at their receptor, as has been implicated from the analysis of an NTPDase1/P2Y 1 receptor fusion protein [165].…”

Purinergic modulation of norepinephrine release and uptake in rat brain cortex: contribution of glial cells

“…An interaction between A 1 and P2Y 1 receptors may explain the attenuation of the ADP␤S inhibitory effect by DPCPX. This interaction may result from the formation of A 1 /P2Y 1 heterooligomers (Nakata et al 2005;Schicker et al 2009), which combine pharmacological properties of the A 1 and P2Y 1 receptors and have been shown to be expressed in the rat brain cortex, hippocampus, and cerebellum (Nakata et al 2005). In functional assays, activation of A 1 /P2Y 1 heterodimers by CPA or ADP␤S caused an inhibition of adenylyl cyclase activity, which was prevented by the A 1 receptor antagonist DPCPX but not by the P2Y 1 receptor antagonist MRS 2179 (Yoshioka and Nakata 2004).…”

“…This problem has been partially overcome by using agonists metabolically more stable and by blocking the A 1 receptors, the main adenosine receptors involved in the modulation of transmitter release in the brain (Fredholm et al 2005). Additionally, several P2Y and adenosine receptors such as P2Y 1 , P2Y 2 , P2Y 12 , P2Y 13 , A 1 , and A 2A receptors may interact physically, forming heterooligomers between them but also with NTPDase1 (Nakata et al 2005;Schicker et al 2009), or may interact functionally (Quintas et al 2009;Tonazzini et al 2007), both mechanisms contributing to confound even more the identification of individual P2Y receptor subtypes involved in the regulation of synaptic transmission.…”

Extracellular ATP signaling in plants

“…The nucleotides are rapidly hydrolyzed by ecto-nucleotidases or ecto-apyrases [28]. Interestingly, CD39 ecto-apyrase can form hetero-oligomer complexes with G protein-coupled receptors for nucleotides or nucleosides [29]. Thus, purinergic signaling is achieved via the expression of receptors and ecto-enzymes and through their direct interaction within a multifarious membrane network.…”