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Morphological differentiation of rat pheochromocytoma cells (PC12 cells) by electric stimulation.

The effects of electric stimulation on the morphological differentiation of PC12 cells are described. PC12 cells were stimulated with the 'theta' (4-7 Hz electroencephalogram (EEG) rhythm) pattern-electric stimulation, which was known to elicit stable long-term potentiation (LTP) in the CA1 region of the hippocampus. The stimulation induced the neurite outgrowth of PC12 cells, as well as nerve growth factor (NGF). This result suggests that the electric signal has a differentiating potential equivalent to the receptor-ligand interaction.

Animals↗

Repeated, intermittent treatment with amphetamine induces neurite outgrowth in rat pheochromocytoma cells (PC12 cells).

Repeated, intermittent treatment with amphetamine (AMPH) leads to long-term neurobiological adaptations in rat brain including an increased number and branching of dendritic spines. This effect depends upon several different cell types in the intact brain. Here we demonstrate that repeated, intermittent AMPH treatment induces neurite outgrowth in cultured PC12 cells without the requirement for integrated synaptic pathways. PC12 cells were treated with 1 micro M AMPH for 5 min a day, for 5 days. After 10 days of withdrawal, there was an increase in the percentage of cells with neurites ( approximately 30%) and the length of neurites as well as an increase in the level of GAP-43 and neurofilament-M. Neurite outgrowth was enhanced as withdrawal time was increased. Neurite outgrowth was much greater following repeated, intermittent treatment with AMPH compared to continuous or single treatment with AMPH. Pretreatment with cocaine, a monoamine transporter blocker, inhibited the AMPH-mediated increase in neurite outgrowth. Neither NGF antibody nor DA receptor antagonists blocked AMPH-induced neurite outgrowth, demonstrating that AMPH-induced neurite outgrowth is not dependent on endogenous NGF release or DA receptors. Thus we have demonstrated that repeated, intermittent treatment with AMPH has a neurotrophic effect in PC12 cells. The effect requires the action of AMPH on the norepinephrine transporter, and shares characteristics in its development with other forms of sensitization but does not require an intact neuroanatomy.

Adaptation, Physiological↗

Rapid sprouting of filopodia in nerve terminals of chromaffin cells, PC12 cells, and dorsal root neurons induced by electrical stimulation.

Rapid morphological changes induced by direct electrical stimulation of nerve terminals were studied by using video-enhanced differential interference contrast microscopy at a very high magnification (12,000x). We used mainly cultured bovine chromaffin cells, which developed neurite-like processes, and PC12 cells, which showed neuronal differentiation upon NGF treatment. In a few cases, primary neurons of the rat dorsal root ganglion were also examined. Brief pulse stimulation of the terminals and varicosities induced exocytosis accompanied by rapid formation of filopodia. These filopodia, 0.1-0.2 micron in diameter and up to 10 microns in length, formed within a few hundreds of milliseconds and then retracted within tens of seconds. They could also be induced by K depolarization. This rapid filopodial sprouting strongly depended on the presence of extracellular Ca2+ and could be abolished in a medium containing a Ca chelator (EGTA) or La2+. Anti-cytoskeletal agents colchicine and cytochalasin B failed to block this response completely but lidocaine fully suppressed it. Quantitative analysis of exocytosis and filopodial sprouting showed that they were independent events, not directly linked to each other, having different thresholds usually higher for filopodial formation. In PC12 cells, the extent of filopodial sprouting varied with the state of differentiation of the cells, suggesting a functional role of rapid sprouting during a particular phase of their differentiation. Filopodia could be induced with greater ease by repetitive stimulation. The same responses may occur at growth cones approaching the target cells or even at mature synapses particularly after repetitive electrical activity, possibly playing a role in use-dependent synapse formation or plasticity.

Aging↗

Repeated amphetamine treatment induces neurite outgrowth and enhanced amphetamine-stimulated dopamine release in rat pheochromocytoma cells (PC12 cells) via a protein kinase C- and mitogen activated protein kinase-dependent mechanism.

Repeated intermittent treatment with amphetamine (AMPH) induces both neurite outgrowth and enhanced AMPH-stimulated dopamine (DA) release in PC12 cells. We investigated the role of protein kinases in the induction of these AMPH-mediated events by using inhibitors of protein kinase C (PKC), mitogen activated protein kinase (MAP kinase) or protein kinase A (PKA). PKC inhibitors chelerythrine (100 nm and 300 nm), Ro31-8220 (300 nm) and the MAP kinase kinase inhibitor, PD98059 (30 micro m) inhibited the ability of AMPH to elicit both neurite outgrowth and the enhanced AMPH-stimulated DA release. The direct-acting PKC activator, 12-O-tetradecanoyl phorbol 13-acetate (TPA, 250 nm) mimicked the ability of AMPH to elicit neurite outgrowth and enhanced DA release. On the contrary, a selective PKA inhibitor, 100 micro m Rp-8-Br-cAMPS, blocked only the development of AMPH-stimulated DA release but not the neurite outgrowth. Treatment of the cells with acute AMPH elicited an increase in the activity of PKC and MAP kinase but not PKA. These results demonstrated that AMPH-induced increases in MAP kinase and PKC are important for induction of both the enhancement in transporter-mediated DA release and neurite outgrowth but PKA was only required for the enhancement in AMPH-stimulated DA release. Therefore the mechanisms by which AMPH induces neurite outgrowth and the enhancement in AMPH-stimulated DA release can be differentiated.

Amphetamine↗

Serum-free culture conditions for serial subculture of undifferentiated PC12 cells.

PC12 cells, a widely used model neuronal cell line, are usually cultured in serum-supplemented medium. This report describes a serum-free medium for the culture of PC12 cells. PC12 cells grown in the two media types had similar growth rates and released dopamine in response to high potassium-induced calcium elevation. However, the levels of dopamine and of dopamine release in cells cultured in the serum-free medium were less than 10% of that in cells cultured in serum-supplemented medium. Dopamine levels recovered within 10 days if cells were returned to serum-supplemented medium, but dopamine release could not be recovered. Nerve growth factor (NGF) induced similar responses in PC12 cells cultured in both media, including phosphorylation of extracellular signal-regulated protein kinases and neurite extension. Transferrin was necessary for survival of neurite-bearing PC12 cells subcultured in serum-free medium and insulin promoted the cells proliferation. Ten days culture with NGF produced a similar increase in neurofilament expression and acetylcholinesterase activity in both media. These results suggest that PC12 in the hormonally defined serum-free media are qualitatively the same as those cultured in serum-supplemented media, and therefore this new culture protocol should enable more precise studies of PC12 cells culture in the absence of confounding unknown factors.

Acetylcholinesterase↗

Effects of oxidative stress on prion protein expression in PC12 cells.

PC12 cells are known to express the prion protein, a normal cell surface glycoprotein. This protein is upregulated in PC12 cells differentiated with nerve growth factor. A neurotoxic prion protein peptide, PrP106-126, is not toxic to PC12 cells alone. PrP106-126 is toxic to PC12 cells co-cultured with microglia and more so to NGF-differentiated PC12 cells. PC12 cells selected for resistance to either copper toxicity or oxidative stress have higher levels of PrP(C) expression. Both PC12 variants are more sensitive to the toxicity of PrP106-126. This suggests that PC12 sensitivity to PrP106-126 toxicity is related to prion protein expression and not to a state of high differentiation induced by NGF. Variants of PC12 cells that are more resistant to copper toxicity have higher levels of anti-oxidant enzymes, superoxide dismutase and glutathione peroxidase. Our results suggest that cells expressing higher levels of PrP(C) have higher resistance to oxidative stress or copper toxicity but are more sensitive to PrP106-126 toxicity. Prion protein expression may be involved in both the metabolism of copper and resistance to oxidative stress. Increased cellular resistance to copper toxicity may be partly related to increased activity of anti-oxidant enzymes.

Animals↗

Need for caspases in apoptosis of trophic factor-deprived PC12 cells.

PC12 cells are a useful model system for studying neuronal apoptosis. Like neurons, they undergo apoptosis when deprived of trophic support. Involvement of caspases [interleukin 1beta-converting enzyme (ICE)-related proteases] has been implicated in apoptosis induced by various stimuli in many cell types, including neurons. In the present study we investigated the need for caspases participation in apoptosis induced by growth factor deprivation in naive and neuronal PC12 cells. For this purpose we generated PC12 cell lines that consistently express the viral caspases inhibitor genes p35 or crmA, and analyzed their susceptibility to trophic factor deprivation. We also examined the effects of cell-permeable peptide inhibitors of caspases. Our results showed that broad-spectrum inhibitors of the caspases, namely the baculovirus p35 gene and the peptide benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone, effectively inhibit the death of both naive and neuronal PC12 cells. However, caspase-1 (ICE)-specific inhibitors, namely the peptides Ac-Try-Val-Ala-Asp-chloromethylketone and Ac-Try-Val-Ala-Asp-aldehyde, as well as crmA, were much less effective. These findings demonstrate that caspases, but not caspase-1, are needed for apoptosis induced by trophic factor deprivation in both naive and neuronal PC12 cells. Northern and Western blot analyses showed that PC12 cells express caspase-3. We therefore examined the involvement of caspase-3 in the death process of trophic factor-deprived PC12 cells. Our results showed that the pro-caspase-3 and its substrate poly-(ADP-ribose) polymerase are cleaved at similar rates in serum-deprived PC12 cells. Moreover, cell lysates prepared from these cells possess caspase-3-like activity, as determined by their ability to cleave the fluorogenic peptide substrate Ac-Asp-Glu-Val-Asp-7-amino-4-methylcoumarin. These findings strongly suggest that caspase-3 or caspase-3-like proteases are activated in trophic factor-deprived PC12 cells.

Amino Acid Chloromethyl Ketones↗

Neurotoxicity of 25-OH-cholesterol on NGF-differentiated PC12 cells.

PC12 cells induced to differentiate with nerve growth factor were used to study the neurotoxicity of 25-OH-cholesterol. This agent induced a dose- and time-dependent cell death in neuronal PC12 cells. Cells treated with this agent showed condensed nuclei, a morphology similar to that of cells dying of programmed cell death. However, agents known to prevent neuronal programmed cell death (cyclic AMP, KCl, aurintricarboxylic acid, and cycloheximide) failed to prevent the 25-OH-cholesterol-mediated cytotoxicity. On the other hand, cell death induced by 25-OH-cholesterol was prevented by treatment with vitamin E and methyl-beta-cyclodextrin. In contrast to observations made in other cell types, whole-cell patch clamp recording of neuronal PC12 cells revealed that treatment with 25-OH-cholesterol did not significantly alter calcium influx through voltage-dependent channels. These results provide the first characterization of the toxicity of cholesterol oxides toward neuronal PC12 cells, which should be useful in future studies on the interactions between cholesterol oxides and cells from the nervous system.

Animals↗

Translational activity of N-methyl-D-aspartate receptor subunit NR1 mRNA in PC12 cells.

PC12 cells contain NR1 mRNA but lack significant expression of NR1 protein suggesting translational or posttranslational regulation. Translational activity of NR1 mRNA in PC12 cells was examined by sucrose gradient fractionation and by heterologous luciferase NR1 gene expression studies. The cosedimentation and association of NR1 mRNA with large polyribosomes (polysomes) confirmed the translatability of NR1 message in PC12 cells. Possible initiation and/or elongation defects during the translation of NR1 mRNAs were investigated by cyclohexamide treatment. The marked decline in the number of ribosomes associated with NR1 mRNA after prolonged exposure to cyclohexamide suggested that initiation was limiting translation of NR1 mRNA in PC12 cells. Consequently, the effect of the 5' and 3' untranslated regions (UTRs) on translation was examined using fusion constructs consisting of the luciferase coding region fused to either or both the 5' UTR and 3' UTR of NR1. The transfection of PC12 cells with the luciferase NR1-UTR fusion constructs revealed that the 3' UTR of NR1 had a significant inhibitory effect on luciferase expression. In contrast, the 5' UTR of NR1 had no inhibitory effect on mRNA translation in PC12 cells. The results from this study indicate that the translation of NR1 mRNA in PC12 cells may be impeded at initiation and this inhibition may be regulated at least in part through the 3' UTR of NR1.

5' Untranslated Regions↗

Signaling pathways activated by alpha1-adrenergic receptor subtypes in PC12 cells.

PC12 cells were used to compare signaling pathways activated by alpha1-adrenergic receptor (AR) subtypes. PC12 cells were transfected with human alpha1A, alpha1B, or alpha1D-ARs, and subclones stably expressing receptor densities in physiological ranges isolated and characterized. Norepinephrine (NE) activated a large number of signaling pathways in transfected cells, including inositol phosphate formation, intracellular calcium, all three arms of the mitogen activated protein kinase pathways, and a number of tyrosine kinases. Activation of mitogen activated protein kinase pathways and tyrosine kinases was not blocked by chelation of intracellular calcium with BAPTA or inhibition of protein kinase C. NE also activated luciferase reporter constructs for seven different transcription factors (AP1, SRE, CRE, NFkappaB, NFAT, Stat, GAS) following transfection into alpha1A-AR expressing PC12 cells. However, similar increases in inositol phosphate formation and intracellular Ca2+ caused by purinergic P2Y2 receptor activation did not activate any of these reporters. Comparison of alpha1-AR subtypes showed that the alpha1A activated all seven reporters, the alpha1B showed smaller effects, while the alpha1D was ineffective. NE caused differentiation of alpha1A, but not alpha1B or alpha1D, -AR expressing PC12 cells similar to that caused by NGF. This NE-induced differentiation was reduced or blocked by all inhibitors tested. We conclude that alpha1-ARs activate many signaling pathways and transcriptional responses in PC12 cells, which are not linearly related to second messenger production, and which may differ for different alpha1-AR subtypes.

Animals↗

Proteomic analysis of rat pheochromocytoma PC12 cells.

PC12 cell line is well documented and widely applied as many kinds of models in neurobiological and neurochemical studies. Yet a thorough proteomic analysis has not been performed so far. Here we report the construction of a large-scale 2-D protein database for PC12 cells. The proteins extracted from PC12 cells were separated by 2-DE and identified by MALDI-TOF/TOF MS. A total of 1080 protein spots, excised from three different 2-D gels, were identified with high confidence. These proteins represent 474 different gene products, mainly binding proteins and enzymes. Three hundred and seven identified protein spots were located in the low-molecular weight region below 20 kDa. This database today represents one of the largest 2-D databases for higher eukaryotic cell proteomes and for low-molecular weight proteins. In addition, fragment ion spectra obtained by TOF/TOF confirmed that calcylin in PC12 cells was N-acetylated. The database of PC12 proteome is expected to be a powerful tool for neuroscientists.

Animals↗

IFNgamma and TNFalpha synergistically induce neurite outgrowth on PC12 cells.

PC12 cells are commonly used in the study of neuronal cells. It was reported that IFNgamma enhances neurite outgrowth of PC12 cells by NGF-stimuli. Accordingly, IFNgamma was examined to determine if it could solely produce neurite outgrowth. In addition, because the synergism between TNFalpha and IFNgamma is well-known, this study investigated whether or not a mixture of IFNgamma and TNFalpha might augment neurite outgrowth on PC12 cells. Finally, this study examined how an AG490 treatment, which was used to inhibit the IFNgamma signal in this study, affected the cytokine-mediated phenomenon. The results showed that the cytokines did not cause an increase in apoptosis in the PC12 cells and the serum-starved condition blocked the cytokine-mediated neurite outgrowth. Interestingly, AG490 enhanced this effect. In conclusion, it was shown that IFNgamma has the potential to form neurites, and TNFalpha can enhance this ability.

Animals↗

Nerve growth factor-induced neuronal differentiation is accompanied by differential induction and localization of the amyloid precursor protein (APP) in PC12 cells and variant PC12S cells.

PC12 cells and the morphological variant PC12S cells in culture were examined by immunochemical methods for the presence of the amyloid precursor protein (APP), before and after treatment with the nerve growth factor (NGF). In untreated PC12, untreated PC12S and in NGF-treated PC12 cells, APP was localized in the cytoplasm, whereas in NGF-treated PC12S cells, APP was localized at growth cones, processes and cytoplasm. In PC12 cells, three major forms of APP (695 and 751/770) were detected by Western blot. After NGF treatment, only the level of APP 695 was increased. Immunoprecipitation studies in PC12 cells revealed six protein species, corresponding to immature and mature forms of each of the three APP 695, 751 and 770 proteins. Addition of NGF increased the synthesis of the immature and mature forms of APP695. In PC12S cells, only the higher molecular weight forms of APP (751/770) were detected by both Western blot and immunoprecipitation. Addition of NGF had no effect on their levels. In both cell types, the level of the secreted form of APP showed a significant transient increase after NGF treatment. These results suggest that NGF can differentially regulate the molecular forms of APP and the localization of APP within the cell.

Amyloid beta-Protein Precursor↗

Down-regulation of adenosine A2A receptors upon NGF-induced differentiation of PC12 cells.

PC12 cell differentiation was induced by one week of nerve growth factor (NGF) treatment and adenosine A2A receptor expression and activity were analysed. Undifferentiated PC12 cells expressed very high levels of adenosine A2A receptors (approximately equal to 2 pmol/mg) and exhibited strong cyclic AMP (cAMP) responses when stimulated with the selective adenosine A2A receptor agonist 2-[p-(2-carbonylethyl) phenylethylamino-5'-N-ethylcarboxamidoadenosine]. NGF-induced differentiation was accompanied by a down-regulation of adenosine A2A receptors: receptor binding decreased to 500 fmol/mg, immunoreactive A2A receptor protein was decreased by about half and cAMP production was reduced by 60%. In situ hybridization experiments demonstrated a heterogenous distribution of A2A receptor mRNA and a decreased number of strongly labelled cells after NGF treatment. Stimulation of the cells with the non-selective adenosine receptor agonist N-ethylcarboxamidoadenosine (NECA) inhibited NGF-induced mitogen-activated protein kinase activation. These results thus show that NGF-induced differentiation of PC12 cells is accompanied by a decrease in A2A receptor-mediated cAMP accumulation. This might be a way for PC12 cells to counteract an inhibitory effect of A2A receptor activation on some aspects of neurotrophin signalling.

Animals↗

Characterization of synaptic vesicles and related neuronal features in nerve growth factor and ras oncogene differentiated PC12 cells.

PC12 cells can differentiate into neuron-like cells after treatment with either nerve growth factor (NGF) or transduction with a retrovirus which expresses the K-ras oncogene. The concomitant treatment of NGF plus ras differentiates PC12 cells further than either agent alone with respect to neurite outgrowth, acetylcholinesterase levels, and most strikingly, the number of synaptic vesicle (SV) clusters. These SV clusters in PC12 cell neurites closely resemble those in the presynaptic terminals of neurons. Such SV clusters have not been described in cell lines previously. The SV clusters from all three differentiated groups (NGF, ras, and NGF plus ras) were similar in size, shape, and configuration, except that the ones in the doubly treated group occur in higher frequency and have more vesicles. The synaptic nature of these vesicle clusters was demonstrated by their regulated depletion after potassium stimulation. Furthermore, these vesicle clusters stained positively for two SV-associated proteins, synapsin I and synaptophysin, by EM immunocytochemistry (ICC). Such SV clusters in a cell line are very useful for characterizing the regulated release of SVs and the distribution of SV-related antigens in intact cells. Analysis by SDS-gel electrophoresis and immunoblotting indicated that synapsin I levels are higher in all three differentiated groups compared to untreated cells; whereas synaptophysin levels are lower in cells exposed to NGF alone or with NGF and ras double treatment. Possible convergence and/or divergence on the mechanisms of NGF and ras differentiation in PC12 cells are discussed.

Acetylcholinesterase↗

Characterization of myosin V from PC12 cells.

PC12 cell line is a cellular model to study neurite outgrowth and neurotransmitter release mechanisms. Molecular motors may be involved in these responses and myosin V could be a candidate to mediate these effects. Overlay experiments using [(125)I]-calmodulin showed that PC12 cells possess several calmodulin-binding proteins, some of them around 190-210 kDa. Western blots using affinity purified polyclonal antibodies raised against chicken brain myosin V revealed a component of 190 kDa, a molecular mass typical of myosin V. Furthermore, Northern blots using a myosin V probe also detected a transcript of around 12 kbp. Immunofluorescence cytochemistry demonstrated the localization of myosin V throughout the cytoplasm, in the neurites, growth cone tips, and with an intense asymmetrical perinuclear labeling. Western blot analyses of PC12 cellular extracts after FGF-2 and/or dibutyryl cAMP treatment revealed variations between myosin V and myosin II expression during neuronal differentiation. These results demonstrated the presence of myosin V in PC12 cells and also suggest a role for this motor molecule in the neuronal differentiation response in PC12 cells.

Animals↗

The small Gtpase ras is involved in growth factor-regulated expression of the alpha1 integrin subunit in PC12 cells.

PC12 cells interact with several growth factors (e. g. EGF, FGF, and NGF) via specific tyrosine receptor kinases, resulting in cell proliferation or neuronal differentiation. The small GTPase Ras is known to be involved in downstream signaling of these growth factor receptors. Furthermore, cell-matrix interactions mediated by integrins, as well as integrin-induced signaling, are also involved in growth factor-stimulated signal transduction in PC12 cells. In this study we determined the expression of the alpha1 integrin subunit in response to EGF and NGF in PC12 wild-type (wt) cells, and in PC12 cells overexpressing an inactive H-Ras protein (RasN17). In PC12 wt cells, alpha1 integrin expression is upregulated by EGF and NGF. Cell surface expression of alpha1beta1integrin is also enhanced in growth factor-treated cells. This upregulation leads to increased alpha1beta1-specific adhesion to collagen. In cells expressing the dominant-negative RasN17 variant, alpha1 integrin expression and alpha1beta1-specific adhesion remain unchanged in response to both growth factors.

Animals↗

Genetic elements regulating HES-1 induction in Wnt-1-transformed PC12 cells.

PC12 cells differentiate in response to nerve growth factor from a chromaffin cell to a sympathetic neuronal phenotype. Wnt-1 is a secreted signaling factor required for development of mammalian midbrain and cerebellum. PC12 cells transformed by Wnt-1 fail to express several differentiation-specific genes in response to nerve growth factor. We have previously shown that HES-1, a negative regulator of neuronal differentiation, is increased in Wnt-1/PC12 cells (P. S. Issack and E. B. Ziff. Altered expression of helix-loop-helix transcriptional regulators and cyclin D1 in Wnt-1-transformed PC12 cells. Cell Growth & Differ., 9: 837-845). Here, we show that the HES-1 promoter is more active in Wnt-1/PC12 cells relative to PC12 and that the binding sites for the transcription factor RBP-J kappa contribute to this induction. We also identify two additional promoter elements required for elevated HES-1 expression. One element binds Wnt-1-induced protein complexes in a sequence-specific manner. Identification of Wnt-1 responsive elements in potential target genes may provide clues to nuclear pathways regulated by Wnt-1.

Animals↗