Neurite Outgrowth of Mature Retinal Ganglion Cells and PC12 Cells Requires Activity of CK1δ and CK1ε

Department of General, Visceral and Transplantation Surgery, University of Ulm, Ulm, Germany.
PLoS ONE (Impact Factor: 3.23). 06/2011; 6(6):e20857. DOI: 10.1371/journal.pone.0020857
Source: PubMed


Mature retinal ganglion cells (RGCs) do not normally regenerate severed axons after optic nerve injury and show only little neurite outgrowth in culture. However, RGCs can be transformed into an active regenerative state after lens injury (LI) enabling these neurons to regrow axons in vitro and in vivo. In the current study we investigated the role of CK1δ and CK1ε activity in neurite outgrowth of LI stimulated RGCs and nerve growth factor (NGF) stimulated PC12 cells, respectively. In both cell types CK1δ and ε were localized in granular particles aligned at microtubules in neurites and growth cones. Although LI treatment did not measurably affect the expression of CK1δ and ε, it significantly elevated the specific kinase activity in the retina. Similarly, CK1δ/ε specific kinase activity was also elevated in NGF treated PC12 cells compared with untreated controls. Neurite extension in PC12 cells was associated with a change in the activity of CK1δ C-terminal targeting kinases, suggesting that activity of these kinases might be necessary for neurite outgrowth. Pharmacological inactivation of CK1δ and ε markedly compromised neurite outgrowth of both, PC12 cells and LI stimulated RGCs in a concentration dependent manner. These data provide evidence for a so far unknown, but essential role of CK1 isoforms in neurite growth.

Download full-text


Available from: Uwe Knippschild
  • Source
    • "CKIα, δ, and ε involved in vesicular trafficking [16–18] are also implicated in canonical Wnt signaling, but with distinct role [19]. CKIδ transduces specific centrosome functions [20], but, like CKIε, it also contributes to the regulation of the circadian rhythm [21, 22], apoptosis [23], and neuronal neurite outgrowth [24]. Interestingly, among the CKI family, the closely related CKIγ proteins (CKIγ1, 2, and 3) are unique in carrying C-terminal lipid modification motif that is believed to anchor them at the plasma membrane [25, 26]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Actin cytoskeleton remodeling is under the regulation of multiple proteins with various activities. Here, we demonstrate that the γ2 isoform of Casein Kinase I (CKIγ2) is part of a novel molecular path regulating the formation of actin stress fibers. We show that overexpression of CKIγ2 in fibroblasts alters cell morphology by impairing actin stress fibers formation. We demonstrate that this is concomitant with increased phosphorylation of the CDK inhibitor p27(Kip) and lower levels of activated RhoA, and is dependent on CKIγ2 catalytic activity. Moreover, we report that roscovitine, a potent inhibitor of cyclin-dependent kinases, including Cdk5, decreases p27(Kip) protein levels and restores actin stress fibers formation in CKIγ2 overexpressing cells, suggesting the existence of a CKIγ2-Cdk5-p27(Kip)-RhoA pathway in regulating actin remodeling. On the other hand, we also show that in a manner independent of its catalytic activity, CKIγ2 delays cell cycle progression through G1. Collectively our findings reveal that CKIγ2 is a novel player in the control of actin cytoskeleton dynamics and cell proliferation.
    Full-text · Article · Mar 2012 · International Journal of Cell Biology
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Like other neurons of the central nervous system (CNS), retinal ganglion cells (RGCs) are normally unable to regenerate injured axons and instead undergo apoptotic cell death. This regenerative failure leads to lifelong visual deficits after optic nerve damage and is partially attributable to factors located in the inhibitory environment of the forming glial scar and myelin as well as to an insufficient intrinsic ability for axonal regrowth. In addition to its ophthalmological relevance, the optic nerve has long been used as a favorable paradigm for studying regenerative failure in the CNS as a whole. Findings over the last 15 years have shown that, under certain circumstances, mature RGCs can be transformed into an active regenerative state enabling these neurons to survive axotomy and to regenerate axons in the optic nerve. Moreover, combinatorial treatments overcoming the inhibitory environment of the glial scar and optic nerve myelin, together with approaches activating the intrinsic growth program, can further enhance the amount of regeneration in vivo. These findings are encouraging and open the possibility that clinically meaningful regenerationmay become achievable in the future.
    Full-text · Article · Feb 2012 · Cell and Tissue Research
  • [Show abstract] [Hide abstract]
    ABSTRACT: Immunoregulation of mesenchymal stromal cells (MSC) is more efficient at restoring biologic function of injured tissue than transdifferentiation during transplantation. However, the exact mechanisms and characteristics of MSC regarding immunomodulation are still unknown, especially in the damaged niche after hypoxic-ischemic insult. We investigated the anti-apoptotic actions of MSC against the neurotoxicity of hydrogen peroxide (H(2)O(2)) on pheochromocytoma (PC12) cells. To mimic hypoxic-ischemic brain injury in vivo, a relatively high H(2)O(2) concentration and short period were used to treat PC12 cells. MSC were co-cultured directly with the injured PC12 cells, and 5-(3-carboxymethoxyphenyl)-2-(4,5-dimethylthiazoly)-3-(4-sulfophenyl)tetrazolium, inner salt (MTS), lactose dehydrogenase (LDH) and nitric oxide (NO) assays, intracellular Ca(2+) and resting membrane potential (RMP) were analyzed. Apoptotic-associated genes and cytokine releases were detected by reverse transcriptase-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). After exposure to H(2)O(2), the viability of PC12 cells was significantly decreased, while the levels of LDH and NO increased, resulting in intracellular Ca(2+) accumulation and cell apoptosis. Co-culture of MSC with the H(2)O(2)-treated PC12 cells sustained viability of the PC12 cells, reduced LDH levels and NO release, and improved Ca(2+) influx and cell apoptosis. The injured PC12 cells exhibited lower RMP following co-culture with MSC compared with the injured PC12 cells alone. The mRNA expression levels of Bcl-2 were up-regulated and caspase-3 levels down-regulated in the MSC co-culture groups. The release of interleukin (IL)-10 was gradually reduced by co-cultured MSC, while the release of IL-6 was sharply increased following MSC co-culture. These findings indicate that MSC have neuroprotective effects on suppressing cell apoptosis via regulation of the H(2)O(2)-impaired microenvironment, partly through IL-6 and IL-10 cytokine production.
    No preview · Article · Jun 2012 · Cytotherapy
Show more