A cAMP-activated pathway, including PKA and PI3K, regulates neuronal differentiation (original) (raw)
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Cyclic AMP-Induced Neuronal Differentiation via Activation of p38 Mitogen-Activated Protein Kinase
Journal of Neurochemistry, 2002
The p38 mitogen-activated protein kinase (MAPK) pathway mediates cellular responses to inflammatory cytokines and environmental stress, but recent studies have indicated that p38 MAPK may be involved in a more widespread set of cellular functions. Here we show that activation of the cyclic AMP (cAMP) pathway induces a rapid, dose-dependent phosphorylation and activation of p38 MAPK and that combined stimulation with forskolin and growth factors results in additive stimulation of p38 MAPK. Forskolin-stimulated neurite outgrowth in rat pheochromocytoma PC12 cells was inhibited by the p38 MAPK inhibitor SB203580. With the combination of forskolin and nerve growth factor, neurite outgrowth was additively increased, and this effect was also inhibited by SB203580. Finally, transfection of p38AGF, which exhibits a mutated activation loop, inhibited cAMP-mediated neuronal differentiation. The results indicate that p38 MAPK is a downstream target of the cAMP signaling pathway and that p38 MAPK plays a key role in neuronal differentiation induced by cAMP and growth factors by integration of signals from both pathways. Key Words: p38 mitogen-activated protein kinase -Cyclic AMP-Protein kinase A-Neuronal differentiation.
Molecular Pharmacology, 2008
The neurotrophic peptide PACAP (pituitary adenylate cyclaseactivating polypeptide) elevates cAMP in PC12 cells. Forskolin and dibutyryl cAMP mimic PACAP's neuritogenic and cell morphological effects, suggesting that they are driven by cAMP. Comparison of microarray expression profiles after exposure of PC12 cells to either forskolin, dibutyryl cAMP, or PACAP revealed a small group of cAMP-dependent target genes. Neuritogenesis induced by all three agents is protein kinase A (PKA)-independent [not blocked by N-[2-(4-bromocinnamylamino)ethyl]-5-isoquinoline (H89)] and extracellular signal-regulated kinase (ERK)-dependent [blocked by 1,4-diamino-2,3-dicyano-1,4-bis(methylthio) butadiene (U0126)], and therefore cAMP-dependent target genes potentially mediating neuritogenesis were selected for further analysis based on the pharmacological profile of their induction by PACAP (i.e., mimicking that of neuritogenesis). Small interfering RNA (siRNA) targeting one of these genes, Egr1, blocked PACAPinduced neuritogenesis, and siRNA targeting another, Vil2,
Journal of Biological Chemistry, 2002
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.
Differential Effects of cAMP in Neurons and Astrocytes
Journal of Biological Chemistry, 1999
Mitogen-activated protein kinase (MAPK) activation provides cell type-specific signals important for cellular differentiation, proliferation, and survival. Cyclic AMP (cAMP) has divergent effects on MAPK activity depending on whether signaling is through Ras/Raf-1 or Rap1/ B-raf. We found that central nervous system-derived neurons, but not astrocytes, express B-raf. In neurons, cAMP activated MAPK in a Rap1/B-raf-dependent manner, while in astrocytes, cAMP decreased MAPK activity. Inhibition of MAPK in neurons decreased neuronal growth factor-mediated survival, and activation of MAPK by cAMP analogues rescued neurons from death. Furthermore, constitutive expression of B-raf in astrocytoma cells increased MAPK activation, as seen in neurons, and enhanced proliferation. These data provide the first experimental evidence that B-raf is the molecular switch which dominantly permits differential cAMPdependent regulation of MAPK in neurons versus astrocytes, with important implications for both survival and proliferation.
The FASEB Journal, 2012
Both cAMP and ERK are necessary for neuroendocrine cell neuritogenesis, and pituitary adenylate cyclase-activating polypeptide (PACAP) activates each. It is important to know whether cAMP and ERK are arranged in a novel, linear pathway or in two parallel pathways using known signaling mechanisms. Native cellular responses [cAMP elevation, ERK phosphorylation, cAMP responsive element binding (CREB) phosphorylation, and neuritogenesis] and promoter-reporter gene activation after treatment with forskolin, cAMP analogs, and PACAP were measured in Neuroscreen-1 (NS-1) cells, a PC12 variant enabling simultaneous morphological, molecular biological, and biochemical analysis. Forskolin (25 M) and cAMP analogs (8-bromo-cAMP, dibutyryl-cAMP, and 8-chlorophenylthio-cAMP) stimulated ERK phosphorylation and neuritogenesis in NS-1 cells. Both ERK phosphorylation and neuritogenesis were MEK dependent (blocked by 10 M U0126) and PKA independent (insensitive to 30 M H-89 or 100 nM myristoylated protein kinase A inhibitor). CREB phosphorylation induced by PACAP was blocked by H-89. The exchange protein activated by cAMP (Epac)-selective 8-(4-chlorophenylthio)-2=-O-Me-cAMP (100-500 M) activated Rap1 without affecting the other cAMP-dependent processes. Thus, PACAP-38 potently stimulated two distinct and independent cAMP pathways leading to CREB or ERK activation in NS-1 cells. Drug concentrations for appropriate effect were derived from control data for all compounds. In summary, a novel PKA-and Epac-independent signaling pathway: PACAP ¡ adenylate cyclase ¡ cAMP ¡ ERK ¡ neuritogenesis has been identified.-Emery, A. C., Eiden, L. E. Signaling through the neuropeptide GPCR PAC 1 induces neuritogenesis via a single linear cAMP-and ERK-dependent pathway using a novel cAMP sensor.
Cancer Research, 1981
The expression of a adenosine cyclic 3':5'-monophosphate (cAMP)-binding protein, regulatory subunit of the type I cAMPdependent protein kinase (R,), and its functional significance in the differentiation of N-18 mouse neuroblastoma cells were examined. 8-Azidoadenosine cyclic 3':5'-[32P]monophosphate, a photoaffinity-labeling analog of cAMP, and high-resolution sodium dodecyl sulfate-polyacrylamide gel electrophoresis were used to identify and quantitate cAMP-binding proteins in cell extracts. The induction of differentiation of N-18 mouse neuroblastoma cells, initiated either by adding dibutyryl aden osine cyclic 3':5'-monophosphate to the growth medium or by culturing cells in medium supplemented with 1% fetal calf serum, led to a 3-fold increase in the amount of 8-azidoadenosine cyclic 3':5'-[32P]monophosphate incorporated into R,, when assayed in vitro. This increased incorporation was attrib utable to an increase in the amount of RI rather than to an increase in the affinity of R, for 8-azidoadenosine cyclic 3':5'-[32P]monophosphate. The subunit molecular weight, isoelectric point, and immunoreactivity of R, were found to be identical to that of the regulatory subunit of the type I cAMP-dependent protein kinase purified from bovine skeletal muscle. The in crease in RI was not accompanied by an increase in the cAMPdependent protein kinase activity. DEAE-cellulose column chromatography confirmed the induction of R, as a free cAMPbinding protein in the differentiated neuroblastoma cells. The possibility of a growth-dependent regulation of R, was also examined. Addition of 2% dimethyl sulfoxide to cultures of N-18 mouse neuroblastoma cells inhibited cell growth without increasing the specific activity of RI. Dimethyl sulfoxide had no effect on neurite outgrowth or acetylcholinesterase activity, two parameters characteristic of differentiated cells. The fact that the induction of RI coincided with differentiation of the neuroblastoma cells suggests that the expression of RI may be used as a biochemical index of differentiation in these cells. The presence of a free cAMP-binding protein, not associated with cAMP-dependent protein kinase in neuroblastoma cells, raises important considerations concerning the action of cAMP in the regulation of growth and differentiation.
Journal of Neuroscience Research, 1992
The respective roles of CAMP-dependent protein kinase (protein kinase A [PKA]) and protein kinase C (PKC) in the early stages of neurite outgrowth were examined in SH-SY-5Y human neuroblastoma cells. Forskolin or dbcAMP, agents that increase intracel-M a r cAMP levels, and intracellular delivery of PKA catalytic subunit induced neurite outgrowth. The PKA inhibitor, N-(2-guanidinoethyl)-5-isoquinolinesulfonamide (HA 1004), prevented the increases, and decreased further the percentage of cells possessing short, filopodia-like neurites in the absence of inducers. In contrast to effects on PKA activation, PKC activation by 12-0-tetradecanoylphorbol-13-acetate (TPA) reduced the percentage of filopodia-like neurites elaborated by otherwise untreated cells, and prevented neurite outgrowth induced by PKA activators. PKC inhibitors l-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride (H7), staurosporine, and sphingosine induced neurite outgrowth. Neurites induced by PKA activation contained higher levels of tubulin immunoreactivity than those induced by PKC inhibition. Furthermore, PKA-induced neurites rapidly retracted in the presence of colchicine, while those elaborated following PKC inhibition were more resistant. These data suggest that neurites elaborated in response to PKA activation are dependent upon microtubule polymerization, and that neurite induction following PKC inhibition is mediated by a different mechanism. PKA activators and PKC inhibitors exerted additive effects on neurite outgrowth, suggesting that the distinct pathways regulated by these two kinases function cooperatively during neuritogenesis.
A Novel Murine PKA-Related Protein Kinase Involved in Neuronal Differentiation
Genomics, 2000
Members of the cAMP-dependent second-messenger pathway have been described as regulators of cellular growth and differentiation and were consequently implicated in a variety of embryogenic processes including brain development. Moreover, recent data suggest an indispensable role for cAMP-dependent protein kinases (PKAs) in neuronal differentiation and synaptic plasticity. Using a degenerate primer-based approach, we have identified a novel murine gene closely related to the human cAMP-dependent protein kinase PRKX on Xp22.3. This gene (Pkare) was mapped to the region near the centromere of the murine X chromosome and is expressed in a variety of adult organs including kidney, liver, spleen, testis, ovary, lung, heart, and brain. Antisense in situ hybridization on staged mouse embryos revealed a highly distinctive expression pattern during neuronal development, with elevated Pkare expression observed only in differentiating neurons within the first ganglion, the dorsal root ganglia, and the mantle layer of the telencephalon. Based on the close relationship with the catalytic PKA subunits and its distinct expression in differentiating neuronal cells, Pkare might represent a novel component of the cAMP-regulated pathways involved in brain development and function.
Journal of Biological Chemistry, 1998
Induction of neuronal differentiation of the rat pheochromocytoma cell line, PC12 cells, by nerve growth factor (NGF) requires activation of the mitogen-activated protein (MAP) kinase or extracellular signal-regulated kinase (ERK). cAMP-dependent protein kinase (protein kinase A (PKA)) also can induce differentiation of these cells. Like NGF, the ability of PKA to differentiate PC12 cells is associated with a sustained activation of ERKs. Here we show that maximal sustained activation of ERK1 by NGF requires PKA. Inhibitors of PKA partially blocked activation of ERK1 by NGF but had no effect on activation of ERK1 by EGF. Inhibition of PKA also reduced the ability of NGF and cAMP, but not EGF, to activate the transcription factor Elk-1, reduced the induction of both immediate early and late genes after NGF treatment, and blocked the nuclear translocation of ERK1 induced by NGF. We propose that PKA is an important contributor to the activation of ERK1 by NGF and is required for maximal induction of gene expression by NGF.
Cellular Signalling, 2011
Cyclic AMP (cAMP) and neurotrophic factors are known to interact closely to promote neurite outgrowth and neuronal regeneration. Glial cell line-derived neurotrophic factor (GDNF) and its family member neurturin (NTN) transduce signal through a multi-component receptor complex consisting of GDNF family receptor alpha 2 (GFRα2) and Ret receptor tyrosine kinase. Neurons from GFRα2-deficient mice do not promote axonal initiation when stimulated by NTN, consistent with the role of GFRα2 in neuronal outgrowth. Multiple alternatively spliced isoforms of GFRα2 are known to be expressed in the nervous system. GFRα2a and GFRα2c but not GFRα2b promoted neurite outgrowth. It is currently unknown if cAMP signalling is differentially regulated by these isoforms. In this study, NTN activation of GFRα2a and GFRα2c but not GFRα2b induced biphasic ERK1/2 activation and phosphorylation of the major cAMP target CREB. Interestingly, inhibition of cAMP signalling significantly impaired GFRα2a and GFRα2c-mediated neurite outgrowth while cAMP agonists cooperated with GFRα2b to induce neurite outgrowth. Importantly, the specific cAMP effector PKA but not Epac was essential for NTN-induced neurite outgrowth, through transcription and translation-dependent activation of late phase ERK1/2. Taken together, these results not only demonstrated the essential role of cAMP-PKA signalling in NTN-induced biphasic ERK1/2 activation and neurite outgrowth, but also suggested cAMP-PKA signalling as a hitherto unrecognized underlying mechanism contributing to the differential neuritogenic activities of GFRα2 isoforms.