Journal
BRAIN RESEARCH
Volume 1155, Issue -, Pages 116-124Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.brainres.2007.04.057
Keywords
protein kinase C; phosphatase 1/2A; adenosine; NMDA; neuroprotection; excitotoxicity; okadaic acid; epiletogenesis; plasticity
Categories
Funding
- NHLBI NIH HHS [R01 HL059595-04, P50 HL060292-060003, P50 HL060292-090003, HL60292, P50 HL060292, R01 HL059595-03, P50 HL060292-070003, HL59595, P50 HL060292-080003] Funding Source: Medline
- NICHD NIH HHS [P30 HD018655-21, HD18655, P30 HD018655-23, P30 HD018655-22, P30 HD018655-24, P30 HD018655] Funding Source: Medline
Ask authors/readers for more resources
We have previously demonstrated that NMDA receptor-mediated extracellular adenosine accumulation in neuronal cultures is receptor-mediated and requires calcium influx. Because protein kinase C (PKC) is a calcium-dependent enzyme, we hypothesized that activation of PKC might be involved in NMDA-mediated adenosine accumulation. PKC inhibitors, however, did not block NMDA-evoked adenosine accumulation, but rather, stimulated basal adenosine accumulation. These data suggested the possibility that NMDA receptor-mediated adenosine accumulation involves net dephosphorylation rather than phosphorylation of one or more substrates. Thus, inhibition of kinases would be expected to increase adenosine accumulation and inhibition of phosphatases would be expected to block adenosine accumulation. To test this hypothesis, we used the phosphatase 1/2A inhibitors calyculin A and okadaic acid. Both inhibitors significantly reduced NMDA-evoked adenosine accumulation. In contrast phosphatase 2B inhibitors did not block NMDA-evoked adenosine accumulation. These data suggest that NMDA-evoked adenosine accumulation is mediated by activation of phosphatase 1/2A. We have established previously that NMDA-mediated adenosine accumulation is associated with adenosine kinase inhibition. However, adenosine kinase is not a direct substrate for phosphatase 1/2A because inhibition of phosphatase 1/2A did not abolish NMDA-evoked adenosine kinase inhibition. Okadaic acid also had no effect on NO donor-evoked adenosine accumulation, which previously has been shown to be associated with adenosine kinase inhibition. Dephosphorylation of one or more proteins other than adenosine kinase as a consequence of NMDA receptor activation might play an important role in extracellular adenosine regulation, with important consequences for the regulation of excitatory synaptic transmission, plasticity, epileptogenesis, and excitotoxicity. (C) 2007 Elsevier B.V. All rights reserved.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available