Rho GTPases in neurite outgrowth

Rho GTPases in neurite outgrowth

Field: Development and regeneration

Authors: Trollér, Ulrika
Zeidman, Ruth
Larsson, Christer

Address of presenting
author: Lund University
Dept. of Laboratory Medicine,
Molecular Medicine, Entrance 78, 3rd floor
University Hospital MAS
S-205 02 Malmö

E-mail: Ulrika.Troller@molmed.mas.lu.se

Phone: 040-337455

Fax: 040-337322

Text of abstract: Rho family GTPases control various cellular processes, including the regulation of cytoskeletal organization. In many cell types it has been shown that Rac1 regulate the formation lamellipodia and membrane ruffles, Cdc42 regulates the formation of filopodia and RhoA controls the assembly of stess fibers and focal adhesion formation. Activation of Rho has also been shown to cause neurite retraction in neuronal cells. Here we have investigated the role of the Rho GTPases in neuroblastoma cell lines by inducing neurite outgrowth in cells expressing dominant negative or constitutively active RhoA, Rac or Cdc42. Initially, we stimulated outgrowth by overexpressing full-length (eFLE) or the regulatory domain (eRDE) of PKCe, which has previously been shown to induce neurites. The induction of neurites by eRDE is higher than by eFLE suggesting that the full-length protein needs to be modified in order to be fully active in terms of neurite induction. Our results show that neurite outgrowth is clearly suppressed by all the constitutively active constructs. Both Rac and Cdc42 dominant negative mutants also showed a suppression although not to the same extent. However, dominant negative RhoA potentiated the neurite outgrowth in cells expressing the regulatory domain of PKCe, while suppressing the full-length PKCe. This indicate that active RhoA could be important for the activation of PKCe and that the inhibitory effect of constitutively active RhoA acts downstream of PKCe. We also investigated the effects on neurite outgrowth in cells stimulated by either NGF or retinoic acid (RA). The same potentiation as seen with eRDE for dominant negative Rho was seen in NGF stimulated cells, while all GTPase mutants showed suppression in RA stimulated cells, indicating different signalling pathways for NGF and RA.

Keywords: rho, protein kinase C, neurite outgrowth, neuroblastoma

	Rho GTPases in neurite outgrowth
Field:	Development and regeneration
Authors:	Trollér, Ulrika Zeidman, Ruth Larsson, Christer
Address of presenting author:	Lund University Dept. of Laboratory Medicine, Molecular Medicine, Entrance 78, 3rd floor University Hospital MAS S-205 02 Malmö
E-mail:	Ulrika.Troller@molmed.mas.lu.se
Phone:	040-337455
Fax:	040-337322
Text of abstract:	Rho family GTPases control various cellular processes, including the regulation of cytoskeletal organization. In many cell types it has been shown that Rac1 regulate the formation lamellipodia and membrane ruffles, Cdc42 regulates the formation of filopodia and RhoA controls the assembly of stess fibers and focal adhesion formation. Activation of Rho has also been shown to cause neurite retraction in neuronal cells. Here we have investigated the role of the Rho GTPases in neuroblastoma cell lines by inducing neurite outgrowth in cells expressing dominant negative or constitutively active RhoA, Rac or Cdc42. Initially, we stimulated outgrowth by overexpressing full-length (eFLE) or the regulatory domain (eRDE) of PKCe, which has previously been shown to induce neurites. The induction of neurites by eRDE is higher than by eFLE suggesting that the full-length protein needs to be modified in order to be fully active in terms of neurite induction. Our results show that neurite outgrowth is clearly suppressed by all the constitutively active constructs. Both Rac and Cdc42 dominant negative mutants also showed a suppression although not to the same extent. However, dominant negative RhoA potentiated the neurite outgrowth in cells expressing the regulatory domain of PKCe, while suppressing the full-length PKCe. This indicate that active RhoA could be important for the activation of PKCe and that the inhibitory effect of constitutively active RhoA acts downstream of PKCe. We also investigated the effects on neurite outgrowth in cells stimulated by either NGF or retinoic acid (RA). The same potentiation as seen with eRDE for dominant negative Rho was seen in NGF stimulated cells, while all GTPase mutants showed suppression in RA stimulated cells, indicating different signalling pathways for NGF and RA.

Keywords:	rho, protein kinase C, neurite outgrowth, neuroblastoma

Index

Created 2000-04-03

Department of Physiological Sciences, Lund University

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