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The mammalian homologue of the Caenorhabditis elegans polarity protein PAR-6 is a binding partner for the RhoGTPases Cdc42 and Rac1
Uppsala University, Units outside the University, Ludwig Institute for Cancer Research.
2000 In: Journal of Cell Science, ISSN 0021-9533, Vol. 113, no 18, 3267-3275 p.Article in journal (Refereed) Published
Place, publisher, year, edition, pages
2000. Vol. 113, no 18, 3267-3275 p.
URN: urn:nbn:se:uu:diva-94196OAI: oai:DiVA.org:uu-94196DiVA: diva2:167966
Available from: 2006-04-05 Created: 2006-04-05Bibliographically approved
In thesis
1. RhoGTPase Signaling in Cell Polarity and Gene Regulation
Open this publication in new window or tab >>RhoGTPase Signaling in Cell Polarity and Gene Regulation
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

RhoGTPases are proteins working as molecular switches as they bind and hydrolyze GTP. They are in their active conformation when GTP is bound and are then able to interact with their effector proteins, which relay the downstream signaling. When the GTP is hydrolyzed to GDP, the RhoGTPase is inactivated. RhoGTPases have been shown to be activated by a variety of stimuli and they are implicated in regulation of diverse cellular processes, including cell migration, cell cycle progression, establishment of cell polarity and transformation.

We identified mammalian Par6 as a novel effector protein for the RhoGTPases Cdc42 and Rac1. The Caenorhabditis elegans homologue of Par6 had previously been shown to be essential for cell polarity development in the worm embryo. We found that endogenous Par6 colocalized with the tight junction protein ZO-1 in MDCKII epithelial cells. Par6 also interacted with mammalian Par3, another member of the par (for partitioning defective) gene family, first identified in C.elegans. Endogenous Par3 also localized to tight junctions in epithelial cells. This suggested that Par6 and Par3 are part of a complex regulating cell polarity also in mammalian cells. The interaction between Par6 and activated Cdc42 and Rac1 suggested a role for these RhoGTPases in the regulation of this complex.

Co-expression of Par6 together with PKCζ, induced a dramatic change in cell morphology. The cells rounded up and long cellular extensions, resembling neurites, were formed. The ability to induce these changes in cell morphology was found to be dependent on the direct interaction between Par6 and PKCζ, as well as on the kinase activity of PKCζ. We observed that cells co-expressing mPar6C and PKCζ contained bundled microtubules and microtubules that hade been acetylated, indicating that the microtubules were stabilized.

To investigate the roles of RhoGTPases in PDGF-induced gene expression we performed cDNA microarray analyses on AG01518 human foreskin fibroblasts in which we over-expressed the dominant negative forms of Cdc42, Rac1 and RhoA. We found that the expression of 16 genes, out of the 45 up-regulated by PDGF-BB, were inhibited ≥50% in the presence of dominant negative Cdc42, Rac1 or RhoA. 19 other genes were down-regulated by one or two of the dominant RhoGTPases. Our data implied that the expression of many PDGF-BB induced genes can be affected by RhoGTPase signaling.

In conclusion, the work presented here has increased the knowledge of the involvement of RhoGTPase signaling in establishment of cell polarity and gene regulation.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2006. 73 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 128
Cell and molecular biology, RhoGTPase, Par6, cell polarity, aPKC, epithelial cell, PDGF, gene regulation, microarray, Cell- och molekylärbiologi
National Category
Biochemistry and Molecular Biology
urn:nbn:se:uu:diva-6698 (URN)91-554-6505-6 (ISBN)
Public defence
2006-04-26, Room B22, BMC, Husargatan 3, Uppsala, 09:15
Available from: 2006-04-05 Created: 2006-04-05Bibliographically approved

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