The activity of the Striatal-enriched protein tyrosine phosphatase in neuronal cells is modulated by adenosine A2A receptor.

We recently demonstrated that a tonic activation of adenosine A2A receptors (A2A Rs) is required for cocaine-induced synaptic depression and increase in the activity of STriatal-Enriched protein tyrosine Phosphatase (STEP). In this study, we elaborated on the relationship between A2A R and STEP using genetic, pharmacological, and cellular tools. We found that the activities of protein tyrosine phosphatases (PTPs), and in particular of STEP, are significantly increased in the striatum and hippocampus of a transgenic rat strain over-expressing the neuronal A2A R (NSEA2A ) with respect to wild-type (WT) rats. Moreover the selective A2A R agonist 4-[2-[[6-Amino-9-(N-ethyl-β-d-ribofuranuronamidosyl)-9H-purin-2-yl]amino]ethyl]benzenepropanoic acid hydrochloride up-regulates PTPs and STEP activities in WT but not in NSEA2A rats, while the selective A2A R antagonist 4-(-2-[7-amino-2-{2-furyl}{1,2,4}triazolo{2,3-a} {1,3,5}triazin-5-yl-amino]ethyl)phenol restores the tyrosine phosphatase activities in NSEA2A , having no effects in WT rats. In addition, while cocaine induced the activation of PTP and STEP in WT rats, it failed to increase phosphatase activity in NSEA2A rats. A2A Rs modulate STEP activity also in the SH-SY5Y neuroblastoma cell line, where a calcium-dependent calcineurin/PP1 pathway was found to play a major role. In summary, the present study identified a novel interaction between A2A R and STEP that could have important clinical implications, since STEP has emerged as key regulator of signaling pathways involved in neurodegenerative and neuropsychiatric diseases and A2A Rs are considered a promising target for the development of therapeutic strategies for different diseases of the central nervous system. Read the Editorial Highlight for this article on page 270.