• BMB Reports
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• v.46 no.12
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• pp.617-622
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• 2013

Rac1 plays a key role in neurite outgrowth via reorganization of the actin cytoskeleton. The molecular mechanisms underlying Rac1-mediated actin dynamics in the cytosol and plasma membrane have been intensively studied, but the nuclear function of Rac1 in neurite outgrowth has not yet been addressed. Using subcellular fractionation and immunocytochemistry, we sought to explore the role of nuclear Rac1 in neurite outgrowth. bFGF, a strong agonist for neurite outgrowth in PC12 cells, stimulated the nuclear accumulation of an active form of Rac1. Rac1-PBR (Q) mutant, in which six basic residues in the polybasic region at the C-terminus were replaced by glutamine, didn't accumulate in the nucleus. In comparison with control cells, cells expressing this mutant form of Rac1 displayed a marked defect in extending neurites that was concomitant with reduced expression of MAP2 and MEK-1. These results suggest that Rac1 translocation to the nucleus functionally correlates with bFGF-induced neurite outgrowth.

• BMB Reports
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• v.44 no.3
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• pp.182-186
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• 2011

Exogenous stimuli such as nerve growth factor (NGF) exert their effects on neurite outgrowth via Trk neurotrophin receptors. TrkA receptors are known to be ubiquitinated via proteasome inhibition in the presence of NGF. However, the effect of proteasome inhibition on neurite outgrowth has not been studied extensively. To clarify these issues, we investigated signaling events in PC12 cells treated with NGF and the proteasome inhibitor MG132. We found that MG132 facilitated NGF-induced neurite outgrowth and potentiated the phosphorylation of the extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK) and phosphatidylinositol-3-kinase (PI3K)/AKT pathways and TrkA receptors. MG132 stimulated internalization of surface TrkA receptor and stabilized intracellular TrkA receptor, and the $Ub^{K63}$ chain was found to be essential for stability. These results indicate that the ubiquitin-proteasome system potentiated neurite formation by regulating the stability of TrkA receptors.

• Archives of Pharmacal Research
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• v.28 no.12
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• pp.1337-1340
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• 2005

A lignan derivative, (-)-(7R, 8S)-dihydrodehydrodiconiferyl alcohol (DHDA), was isolated from Kalopanax septemlobus L. and was observed to have neuritogenic activity. DHDA at 50 $\mu$M caused a marked induction of neurite outgrowth and an enhancement of nerve growth factor (NGF)-mediated neurite outgrowth from PC12 cells. However, it did not exhibit any neurotrophic action. At 50 $\mu$M, DHDA enhanced NGF-induced neurite-bearing activity. This activity was partially blocked by the mitogen-activated protein kinase (MAPK) inhibitor PD98059 and by GF109203X, a protein kinase C (PKC) inhibitor. These results suggest that DHDA can induce neurite outgrowth and enhance NGF-induced neurite outgrowth from PC12 cells by amplifying up-stream steps such as MAPK and PKC.

• International Journal of Oral Biology
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• v.41 no.4
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• pp.231-236
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• 2016

Inhibition of Rho-associated coiled coil-containing kinase (ROCK) has been reported to promote differentiation of neuronal cells. Here, we examined the effect of Y-27632, a ROCK inhibitor, on the outgrowth of neurites in PC12 cells. Y-27632 caused a rapid induction of neurite outgrowth in PC12 cells in a time-dependent manner. The neurite outgrowth, triggered by Y-27632, was accompanied by Rac1 activation, and was attenuated by Rac1 inhibitor NSC23766, in a concentration-dependent manner. Y-27632 also induced an increase in the production of reactive oxygen species (ROS). Pretreatment with N-acetylcysteine, an ROS scavenger, inhibited the ROS generation and neurite outgrowth in response to Y-27632. These results indicate that the activation of Rac1 and the generation of ROS contribute to the neurite outgrowth triggered by Y-27632 in PC12 cells.

• Toxicological Research
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• v.32 no.3
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• pp.239-243
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• 2016

Propolis is a multicomponent, active, complex resinous substance collected by honeybees from a variety of plant sources. We have studied the effect of propolis on neurite outgrowth of SH-SY5Y human neuroblastoma cells induced to differentiate by all-trans-retinoic acid (RA). Propolis, at a concentration of $3{\mu}g/mL$, had no significant effect on the viability of differentiating SH-SY5Y cells. However, the neurite outgrowth of the differentiating SH-SY5Y cells treated with propolis ($0.3{\sim}3{\mu}g/mL$) for 48 hr was significantly inhibited in a dose-dependent manner. Treatment of RA-stimulated differentiating SH-SY5Y cells with 0.3 to $3{\mu}g/mL$ propolis resulted in decreased level of transglutaminase and 43-kDa growth-associated protein (GAP-43) in a dose-dependent manner. The results indicate that propolis is able to inhibit neurite outgrowth of differentiating SH-SY5Y cells.

• Archives of Pharmacal Research
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• v.29 no.12
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• pp.1114-1118
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• 2006

(+)-Eudesmin [4,8-bis(3,4-dimethoxyphenyl)-3,7 -dioxabicyclo[3.3.0]octane] was isolated from the stem bark of Magnolia kobus DC. var. borealis Sarg. and found to have neuritogenic activity. $50\;{\mu}M$ (+)-eudesmin induced neurite outgrowth and enhanced nerve growth factor (NGF)-mediated neurite outgrowth from PC12 cells. At this concentration, (+)-eudesmin also enhanced NGF-induced neurite-bearing activity and this activity was partially blocked by various protein kinase inhibitors. These included PD98059, a mitogen-activated protein kinase (MAPK) kinase inhibitor. GF109203X, a protein kinase C (PKC) inhibitor and H89, a protein kinase A (PKA) inhibitor. These results suggest that (+)-eudesmin can induce neurite outgrowth from PC12 cells by stimulating up-stream MAPK, PKC and PKA pathways.

• Journal of Physiology & Pathology in Korean Medicine
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• v.24 no.4
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• pp.681-687
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• 2010

Sibjeondaebo-tang (SJDBT) is an oriental medicinal prescription for the treatments of diverse symptoms including neurological disorders. In order to investigate its potential role for neural regulation following nerve injury, neurite outgrowth of dorsal root ganglion (DRG) neurons in culture was investigated. In DRG neurons which were preconditioned by sciatic nerve injury, neurite outgrowth was enhanced by SJDBT treatment. When preconditioned DRG neurons were co-cultured with astrocytes prepared from injured spinal cord tissue, neurite outgrowth was similarly facilitated by SJDBT. Astrocytes in co-culture showed more intense signals of vimentin protein by SJDBT compared to saline control. Sukjihwang (SJH), a conventional herbal component of SJDBT prescription, did not induce any significant changes in neurite extension of DRG neurons compared to control cells. These data suggest that SJDBT may be the therapeutic agent for nervous system disorders related to nerve damage.

• Animal cells and systems
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• v.8 no.1
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• pp.57-63
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• 2004

This study provides evidence that expression of EphA8 receptor in NG108-15 cells results in a substantial increase in the number of neurite-bearing cells. However, the EphA8-induced neurite outgrowth does not require either ephrin-A5 stimulation or ectopic expression of $p110{\gamma}$ PI-3 kinase. In contrast, co-expression of a lipid kinase-inactive $p110{\gamma}$ mutant together with EphA8 causes neurite retraction in the presence of ephrin-A5 stimulation. This effect was not observed in the absence of ephrin-A5 stimulation. Significantly, the tyrosine kinase activity of EphA8 is not important for either of these processes. Taken together, our results strongly suggest that $p110{\gamma}$ PI-3 kinase is critically involved in the regulatory process by which ephrin-A5 exerts effects on the EphA8-induced neurite outgrowth.

• BMB Reports
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• v.45 no.9
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• pp.521-525
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• 2012

In addition to its pivotal role in neuronal survival, PI3K/Akt signaling is integral to neuronal differentiation and neurite outgrowth. However, the exact role of Akt in neuronal differentiation is still controversial. Here, we found that nuclear expression of CA-Akt resulted in unusual rapid neurite outgrowth and overexpression of KD-Akt caused multiple dendrite growth without specific axon elongation. Moreover, microarray data revealed that the expression of FOXQ1 expression was about 10-fold higher in cells with nuclear, active Akt than in control cells. Quantitative real-time PCR analysis showed that mRNA levels were upregulated in NLS-CA-Akt cells as compared to KD or EV cells. Furthermore, our FACS analysis demonstrated that overexpression of NLS-CA-Akt accumulate cells in the G1 phase within 24 h, fitting with the rapid sprouting of neuritis. Thus, our data implied that at least in this early time frame, the overexpression of nuclear, active Akt forced cells into neurite development through probably FOXQ1regulation.

• BMB Reports
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• v.33 no.6
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• pp.525-530
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• 2000

The nerve growth factor (NGF) induces neuronal differentiation and neurite outgrowth of PC12 cells, whereas epidermal growth factors (EGF) stimulate growth and proliferation of the cells. In spite of this difference, NGF-or EGF-treated PC12 cells share various properties in cellular-signaling pathways. These include the activation of the phosphoinositide (PI)-3 kinase, 70 kDa S6 kinase, and in the mitogen-activated protein (MAP) kinase pathway, following the binding of these growth factors to intrinsic receptor tyrosine kinases (RTKs). Therefore, many studies have been attempted to access the critical signaling events in determining the differentiation and proliferation of PC12 cells. In this study, we investigated the cytosolic phospholipase $A_2$ ($cPLA_2$) in neurite behavior in order to identify the differences of signaling pathways between the NGF-induced differentiation and the EGF-induced proliferation of PC12 cells. We have showed here that the $cPLA_2$ was translocated from cytosol to membrane only in NGF-treated cells. We also demonstrated that this translocation is associated with NGF-induced activation of phospholipase $C-{\gamma}(PLC-{\gamma})$, which elevates intracellular $Ca^{2+}$ concentration. These results reveal that the translocation of $cPLA_2$ may be a requisite event in the neuronal differentiation of PC12 cells. Various phospholipase inhibitors were used to confirm the importance of these enzymes in the differentiation of PC12 cells. Neomycin B, a PLC inhibitor, dramatically inhibited the neurite outgrowth, and two distinct $PLA_2$ inhibitors, 4-bromophenacyl bromide (BPB) and arachidonyltrifluoro-methyl ketone ($AACOCF_3$) also suppressed the neurite outgrowth of the cells, as well Taken together, these data indicated that $cPLA_2$ is involved in NGF-induced neuronal differentiation and neurite outgrowth of PC12 cells.