Abstract
Protein kinase C (PKC) is a family of serine/threonine kinases subgrouped into classical (α, βI, βII, γ), novel (δ, ε, η, θ) and atypical (ζ, ι/λ) isoforms. PKC can be activated by phorbol esters, and prolonged treatment of neuroblastoma cells has been shown to induce neuronal differentiation with neurite outgrowth and increased expression of neuronal genes. Here we show that a classical PKCβ isoform is important for the phorbol ester-induced gene expression via the MAP kinases Erk 1/2.
A previous study has shown that novel PKCε, via its regulatory domain, induces neurites in neuroblastoma cells. In this thesis we show that membrane localization and an actin-binding site in the regulatory domain is important for this effect. Besides neuroblastoma cells, the regulatory domain of PKCε is sufficient to induce cellular processes in both immortalized neural cells and fibroblasts, indicating that it targets commonly used cytoskeletal proteins. Furthermore, the catalytic activity of PKC is not only dispensable, it counteracts the neurite-inducing capacity of the regulatory domain.
Overexpression of PKCδ does not induce the formation of long cellular extensions by itself. However, treatment with phorbol ester triggers the formation of processes in PKCδ-overexpressing cells. This provides a model system to study initial cytoskeletal changes, which revealed that stress fiber loss accompanies outgrowth of processes. This indicates that the small GTPase RhoA, which is the main regulator of stress fiber formation, is suppressed. Furthermore, overexpression of a constitutively active RhoA blocked both PKC-mediated stress fiber loss and neurite outgrowth. A possible mechanism for the RhoA suppression is via p190RhoGAP, with which PKCε forms a complex. Cdc42 was further shown to be crucial for the PKC-mediated stress fiber loss, and both Rac1 and Cdc42 are important for PKC-mediated outgrowth of cellular processes.
A previous study has shown that novel PKCε, via its regulatory domain, induces neurites in neuroblastoma cells. In this thesis we show that membrane localization and an actin-binding site in the regulatory domain is important for this effect. Besides neuroblastoma cells, the regulatory domain of PKCε is sufficient to induce cellular processes in both immortalized neural cells and fibroblasts, indicating that it targets commonly used cytoskeletal proteins. Furthermore, the catalytic activity of PKC is not only dispensable, it counteracts the neurite-inducing capacity of the regulatory domain.
Overexpression of PKCδ does not induce the formation of long cellular extensions by itself. However, treatment with phorbol ester triggers the formation of processes in PKCδ-overexpressing cells. This provides a model system to study initial cytoskeletal changes, which revealed that stress fiber loss accompanies outgrowth of processes. This indicates that the small GTPase RhoA, which is the main regulator of stress fiber formation, is suppressed. Furthermore, overexpression of a constitutively active RhoA blocked both PKC-mediated stress fiber loss and neurite outgrowth. A possible mechanism for the RhoA suppression is via p190RhoGAP, with which PKCε forms a complex. Cdc42 was further shown to be crucial for the PKC-mediated stress fiber loss, and both Rac1 and Cdc42 are important for PKC-mediated outgrowth of cellular processes.
| Original language | English |
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| Qualification | Doctor |
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| Award date | 2003 Dec 12 |
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| ISBN (Print) | 91-628-5896-3 |
| Publication status | Published - 2003 |
Bibliographical note
Defence detailsDate: 2003-12-12
Time: 10:15
Place: Main lecture hall, Pathology building, entr. 78, University Hospital MAS, Malmö
External reviewer(s)
Name: Fällman, Maria
Title: Dr
Affiliation: Department of Molecular Biology, Umeå University, Sweden
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Article: A PKCβ isoform mediates phorbol ester-induced activation of Erk1/2 and expression of neuronal differentiation genes in neuroblastoma cells.Ulrika Trollér, Ruth Zeidman, Karin Svensson and Christer Larsson.(2001) FEBS Lett. 508, 126-130.
Article: Protein Kinase Cε actin-binding site is important for neurite outgrowth during neuronal differentiation.Ruth Zeidman, Ulrika Trollér, Arathi Raghunath, Sven Påhlman and Christer Larsson.(2002) Mol Biol Cell. 13, 12-24.
Article: Induction of neurites by the regulatory domains of PKCδ and ε is counteracted by PKC catalytic activity and by the RhoA pathway.Mia Ling, Ulrika Trollér, Ruth Zeidman, Cecilia Lundberg and Christer Larsson.Exp Cell Res. (In press)
Article: A possible role for p190RhoGAP in PKCε-induced morphological effects.Ulrika Trollér, Arathi Raghunath and Christer Larsson.Cell Signal. (In Press)
Article: Cdc42 is required for protein kinase C ε- and δ-induced outgrowth of cellular processes and stress fiber dismantling.Ulrika Trollér and Christer Larsson.(Manuscript)
The information about affiliations in this record was updated in December 2015.
The record was previously connected to the following departments: Molecular Medicine (013031200)
Subject classification (UKÄ)
- Cancer and Oncology
Free keywords
- cytogenetics
- Genetik
- cytogenetik
- Rho-family
- actin cytoskeleton
- neurite
- differentiation
- PKC
- regulatory domain
- Genetics
