P2X7 receptors stimulate AKT phosphorylation in astrocytes.
1. Emerging evidence indicates that nucleotide receptors are widely expressed in the nervous system. Here, we present evidence that P2Y and P2X receptors, particularly the P2X(7) subtype, are coupled to the phosphoinositide 3-kinase (PI3K)/Akt pathway in astrocytes. 2. P2Y and P2X receptor agonists ATP, uridine 5'-triphosphate (UTP) and 2',3'-O-(4-benzoyl)-benzoyl ATP (BzATP) stimulated Akt phosphorylation in primary cultures of rat cortical astrocytes. BzATP induced Akt phosphorylation in a concentration- and time-dependent manner, similar to the effect of BzATP on Akt phosphorylation in 1321N1 astrocytoma cells stably transfected with the rat P2X(7) receptor. Activation was maximal at 5 - 10 min and was sustained for 60 min; the EC(50) for BzATP was approximately 50 microM. In rat cortical astrocytes, the positive effect of BzATP on Akt phosphorylation was independent of glutamate release. 3. The effect of BzATP on Akt phosphorylation in rat cortical astrocytes was significantly reduced by the P2X(7) receptor antagonist Brilliant Blue G and the P2X receptor antagonist iso-pyridoxal-5'-phosphate-6-azophenyl-2',4'-disulfonic acid, but was unaffected by trinitrophenyl-ATP, oxidized ATP, suramin and reactive blue 2. 4. Results with specific inhibitors of signal transduction pathways suggest that extracellular and intracellular calcium, PI3K and a Src family kinase are involved in the BzATP-induced Akt phosphorylation pathway. 5. In conclusion, our data indicate that stimulation of astrocytic P2X(7) receptors, as well as other P2 receptors, leads to Akt activation. Thus, signaling by nucleotide receptors in astrocytes may be important in several cellular downstream effects related to the Akt pathway, such as cell cycle and apoptosis regulation, protein synthesis, differentiation and glucose metabolism.
Jacques-Silva
Maria C
MC
Departamento de Bioquímica, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
Rodnight
Richard
R
Lenz
Guido
G
Liao
Zhongji
Z
Kong
Qiongman
Q
Tran
Minh
M
Kang
Yuan
Y
Gonzalez
Fernando A
FA
Weisman
Gary A
GA
Neary
Joseph T
JT
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D018698:Glutamic Acid / Q000378:metabolism; D006801:Humans; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000187:drug effects / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000187:drug effects / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D018048:Receptors, Purinergic P2 / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D058476:Receptors, Purinergic P2X2; D058486:Receptors, Purinergic P2X7; D015398:Signal Transduction / Q000502:physiology; D014544:Uridine Triphosphate / Q000378:metabolism; D019061:src-Family Kinases / Q000378:metabolism
D000255:Adenosine Triphosphate; D002118:Calcium; D018698:Glutamic Acid; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D018048:Receptors, Purinergic P2; D058476:Receptors, Purinergic P2X2; D058486:Receptors, Purinergic P2X7; D014544:Uridine Triphosphate; D019061:src-Family Kinases; C546401:P2RX2 protein, human; C546468:P2RX7 protein, human; C546403:P2rx2 protein, rat; C546470:P2rx7 protein, rat; C033901:3'-O-(4-benzoyl)benzoyladenosine 5'-triphosphate; C494918:AKT1 protein, human; C494920:Akt1 protein, rat