Regulation of RhoA Activation and Actin Reorganization by Diacylglycerol Kinase
type: CreativeWork
description: Rho GTPases are critical regulators of actin cytoskeletal dynamics. The three most well characterized Rho GTPases, Rac1, RhoA and Cdc42 share a common inhibitor, RhoGDI. It is only recently becoming clear how upstream signals cause the selective release of individual Rho GTPases from RhoGDI. For example, our laboratory showed that diacylglycerol kinase zeta (DGKz), which converts diacylglycerol (DAG) to phosphatidic acid (PA), activates PAK1-mediated RhoGDI phosphorylation on Ser-101/174, causing selective Rac1 release and activation. Phosphorylation of RhoGDI on Ser-34 by PKCa has recently been demonstrated to selectively release RhoA, promoting RhoA activation. Here, I show DGKz is required for optimal RhoA activation and RhoGDI Ser-34 phosphorylation. Both were substantially reduced in DGKz-null fibroblasts and occurred independently of DGKz activity, but required a function DGKz PDZ-binding motif. In contrast, Rac1 activation required DGKz-derived PA, but not PDZ-interactions, indicating DGKz regulates these Rho GTPases by two distinct regulatory complexes. Interestingly, RhoA bound directly to the DGKz C1A domain, the same region known to bind Rac1. By direct interactions with RhoA and PKCa, DGKz was required for the efficient co-precipitation of these proteins, suggesting it is important to assemble a signalling complex that functions as a RhoA-specific RhoGDI dissociation complex. Consequently, cells lacking DGKz exhibited decreased RhoA signalling downstream and disrupted stress fibers. Moreover, DGKz loss resulted in decreased stress fiber formation following the expression of a constitutively active RhoA mutant, suggesting it is also important for RhoA function following activation. This is consistent with the ability of DGKz to bind both active and inactive RhoA conformations. Collectively, these findings suggest DGKz is central to two distinct Rho GTPase activation complexes, each having different requirements for DGKz activity and PDZ interactions, and …
abstract: Rho GTPases are critical regulators of actin cytoskeletal dynamics. The three most well characterized Rho GTPases, Rac1, RhoA and Cdc42 share a common inhibitor, RhoGDI. It is only recently becoming clear how upstream signals cause the selective release of individual Rho GTPases from RhoGDI. For example, our laboratory showed that diacylglycerol kinase zeta (DGKz), which converts diacylglycerol (DAG) to phosphatidic acid (PA), activates PAK1-mediated RhoGDI phosphorylation on Ser-101/174, causing selective Rac1 release and activation. Phosphorylation of RhoGDI on Ser-34 by PKCa has recently been demonstrated to selectively release RhoA, promoting RhoA activation. Here, I show DGKz is required for optimal RhoA activation and RhoGDI Ser-34 phosphorylation. Both were substantially reduced in DGKz-null fibroblasts and occurred independently of DGKz activity, but required a function DGKz PDZ-binding motif. In contrast, Rac1 activation required DGKz-derived PA, but not PDZ-interactions, indicating DGKz regulates these Rho GTPases by two distinct regulatory complexes. Interestingly, RhoA bound directly to the DGKz C1A domain, the same region known to bind Rac1. By direct interactions with RhoA and PKCa, DGKz was required for the efficient co-precipitation of these proteins, suggesting it is important to assemble a signalling complex that functions as a RhoA-specific RhoGDI dissociation complex. Consequently, cells lacking DGKz exhibited decreased RhoA signalling downstream and disrupted stress fibers. Moreover, DGKz loss resulted in decreased stress fiber formation following the expression of a constitutively active RhoA mutant, suggesting it is also important for RhoA function following activation. This is consistent with the ability of DGKz to bind both active and inactive RhoA conformations. Collectively, these findings suggest DGKz is central to two distinct Rho GTPase activation complexes, each having different requirements for DGKz activity and PDZ interactions, and …
author: Ard, Ryan
language: en
keywords: Actin, Diacylglycerol Kinase, Rho GTPase, RhoA, Stress Fibers, RhoGDI
date published: 2012-03-22T16:40:16Z
date modified: 2026-07-24T03:39:38Z
provider: University of Ottawa
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Université d'Ottawa / University of Ottawa

PropertyValue
property ID: Handle
value: http://hdl.handle.net/10393/22669

PropertyValue
property ID: DOI
value: 10.20381/ruor-5554