Essential role of cAMP-response element-binding protein activation by A2A adenosine receptors in rescuing the nerve growth factor-induced neurite outgrowth impaired by blockage of the MAPK cascade.
We found in the present study that stimulation of the A(2A) adenosine receptor (A(2A)-R) using an A(2A)-selective agonist (CGS21680) rescued the blockage of nerve growth factor (NGF)-induced neurite outgrowth when the NGF-evoked MAPK cascade was suppressed by an MEK inhibitor (PD98059) or by a dominant-negative MAPK mutant (dnMAPK). This action of A(2A)-R (designated as the A(2A)-rescue effect) can be blocked by two inhibitors of protein kinase A (PKA) and was absent in a PKA-deficient PC12 variant. Activation of the cAMP/PKA pathway by forskolin exerted the same effect as that by A(2A)-R stimulation. PKA, thus, appears to mediate the A(2A)-rescue effect. Results from cAMP-response element-binding protein (CREB) phosphorylation at serine 133, trans-reporting assays, and overexpression of two dominant-negative CREB mutants revealed that A(2A)-R stimulation led to activation of CREB in a PKA-dependent manner and subsequently reversed the damage of NGF-evoked neurite outgrowth by PD98059 or dnMAPK. Expression of an active mutant of CREB readily rescued the NGF-induced neurite outgrowth impaired by dnMAPK, further strengthening the importance of CREB in the NGF-mediated neurite outgrowth process. Moreover, simultaneous activation of the A(2A)-R/PKA/CREB-mediated and the phosphatidylinositol 3-kinase pathways caused neurite outgrowth that was not suppressed by a selective inhibitor of TrkA, indicating that transactivation of TrkA was not involved. Collectively, CREB functions in conjunction with the phosphatidylinositol 3-kinase pathway to mediate the neurite outgrowth process in PC12 cells.
Division of Neuroscience, Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan, Republic of China.
Hsiao-Chun
HC
Cheng
Hsiu-Ming
HM
Shih
Yijuang
Y
Chern
D000818:Animals; D002454:Cell Differentiation; D017362:Cyclic AMP Response Element-Binding Protein / Q000502:physiology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology; D020935:MAP Kinase Signaling System; D020932:Nerve Growth Factor / Q000494:pharmacology*; D016501:Neurites / Q000502:physiology*; D016716:PC12 Cells; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D011493:Protein Kinase C / Q000502:physiology; D051381:Rats; D043705:Receptor, Adenosine A2A; D020917:Receptor, trkA / Q000502:physiology; D018047:Receptors, Purinergic P1 / Q000502:physiology*
D017362:Cyclic AMP Response Element-Binding Protein; D043705:Receptor, Adenosine A2A; D018047:Receptors, Purinergic P1; D020932:Nerve Growth Factor; D019869:Phosphatidylinositol 3-Kinases; D020917:Receptor, trkA; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C