Adenosine deaminase affects ligand-induced signalling by interacting with cell surface adenosine receptors |
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Authors: | Francisco Ciruela Carles Saura Enric I Canela Josefa Mallol Carmen Lluis Rafael Franco |
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Institution: | Departament de Bioquímica i Biologia Molecular, Facultat de Química, Universitat de Barcelona, Martí Franquès 1, Barcelona 08028, Catalonia, Spain |
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Abstract: | Adenosine deaminase (ADA) is not only a cytosolic enzyme but can be found as an ecto-enzyme. At the plasma membrane, an adenosine deaminase binding protein (CD26, also known as dipeptidylpeptidase IV) has been identified but the functional role of this ADA/CD26 complex is unclear. Here by confocal microscopy, affinity chromatography and coprecipitation experiments we show that A1 adenosine receptor (A1R) is a second ecto-ADA binding protein. Binding of ADA to A1R increased its affinity for the ligand thus suggesting that ADA was needed for an effective coupling between A1R and heterotrimeric G proteins. This was confirmed by the fact that ASA, independently of its catalytic behaviour, enhanced the ligand-induced second messenger production via A1R. These findings demonstrate that, apart from the cleavage of adenosine, a further role of ecto-adenosine deaminase on the cell surface is to facilitate the signal transduction via A1R. |
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Keywords: | Adenosine receptor Adenosine deaminase Protein-protein interaction Signal transduction Molecular recognition |
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