Characterization of a Brain-specific Rho GTPase-activating Protein, p200RhoGAP (original) (raw)
Off the beaten paths: alternative and crosstalk regulation of Rho GTPases
The FASEB Journal, 2012
Rho proteins are small GTPases of the Ras superfamily that regulate a wide variety of biological processes, ranging from gene expression to cell migration. Mechanistically, the major Rho GTPases function as molecular switches cycling between an inactive GDP-bound and an active GTP-bound conformation, although several Rho proteins spontaneously exchange nucleotides or are simply devoid of GTPase activity. For over a decade, RhoGEFs and RhoGAPs have been established as the mainstream regulators of Rho proteins, respectively flipping the switch on or off.
The Journal of Cell Biology, 2001
Determinants of membrane targeting of Rho proteins were investigated in live cells with green fluorescent fusion proteins expressed with or without Rhoguanine nucleotide dissociation inhibitor (GDI) ␣ . The hypervariable region determined to which membrane compartment each protein was targeted. Targeting was regulated by binding to RhoGDI ␣ in the case of RhoA, Rac1, Rac2, and Cdc42hs but not RhoB or TC10. Although RhoB localized to the plasma membrane (PM), Golgi, and motile peri-Golgi vesicles, TC10 localized to PMs and endosomes. Inhibition of palmitoylation mislocalized H-Ras, RhoB, and TC10 to the endoplasmic reticulum. Although overexpressed Cdc42hs and Rac2 were observed predominantly on endomembrane, Rac1 was predominantly at the PM. RhoA was cytosolic even when expressed at levels in vast excess of RhoGDI ␣ . Oncogenic Dbl stimulated translocation of green fluorescent protein (GFP)-Rac1, GFP-Cdc42hs, and GFP-RhoA to lamellipodia. RhoGDI binding to GFP-Cdc42hs was not affected by substituting farnesylation for geranylgeranylation. A palmitoylation site inserted into RhoA blocked RhoGDI ␣ binding. Mutations that render RhoA, Cdc42hs, or Rac1, either constitutively active or dominant negative abrogated binding to RhoGDI ␣ and redirected expression to both PMs and internal membranes. Thus, despite the common essential feature of the CAAX (prenylation, AAX tripeptide proteolysis, and carboxyl methylation) motif, the subcellular localizations of Rho GTPases, like their functions, are diverse and dynamic.
Regulation of RhoA GTPase and various transcription factors in the RhoA pathway
Journal of cellular physiology, 2018
RhoA GTPase plays a variety of functions in regulation of cytoskeletal proteins, cellular morphology and migration along with various proliferation and transcriptional activity in cells. RhoA activity is regulated by guanine nucleotide exchange factors (GEFs), GTPase activating proteins (GAPs) and the guanine nucleotide dissociation factor (GDI). The RhoA-RhoGDI complex exists in the cytosol and the active GTP-bound form of RhoA is located to the membrane. GDI displacement factors (GDFs) including IκB kinase γ (IKKγ) dissociate the RhoA-GDI complex, allowing activation of RhoA through GEFs. In addition, modifications of Tyr42 phosphorylation and Cys16/20 oxidation in RhoA and Tyr156 phosphorylation and oxidation of RhoGDI promote the dissociation of the RhoA-RhoGDI complex. The expression of RhoA is regulated through transcriptional factors such as c-Myc, HIF-1α/2α, Stat 6 and NF-κB along with several reported microRNAs. As the role of RhoA in regulating actin-filament formation and...
The Rho GDI Rdi1 Regulates Rho GTPases by Distinct Mechanisms
Molecular Biology of The Cell, 2008
The small guanosine triphosphate (GTP)-binding proteins of the Rho family are implicated in various cell functions, including establishment and maintenance of cell polarity. Activity of Rho guanosine triphosphatases (GTPases) is not only regulated by guanine nucleotide exchange factors and GTPase-activating proteins but also by guanine nucleotide dissociation inhibitors (GDIs). These proteins have the ability to extract Rho proteins from membranes and keep them in an inactive cytosolic complex. Here, we show that Rdi1, the sole Rho GDI of the yeast Saccharomyces cerevisiae, contributes to pseudohyphal growth and mitotic exit. Rdi1 interacts only with Cdc42, Rho1, and Rho4, and it regulates these Rho GTPases by distinct mechanisms. Binding between Rdi1 and Cdc42 as well as Rho1 is modulated by the Cdc42 effector and p21-activated kinase Cla4. After membrane extraction mediated by Rdi1, Rho4 is degraded by a novel mechanism, which includes the glycogen synthase kinase 3 homologue Ygk3, vacuolar proteases, and the proteasome. Together, these results indicate that Rdi1 uses distinct modes of regulation for different Rho GTPases.
Molecular Basis for Rho GTPase Signaling Specificity
Breast Cancer Research and Treatment, 2004
There is now considerable evidence for the involvement of aberrant Rho GTPase activation in breast cancer development. Like Ras, Rho GTPases function as signaling nodes regulated by diverse extracellular stimuli. Rho GTPase activation is facilitated by multiple regulatory proteins, in particular guanine nucleotide exchange factors (GEFs) such as Dbl family proteins. Activated Rho GTPases in turn interact with and regulate a spectrum of functionally diverse downstream effectors, initiating a network of cytoplasmic and nuclear signaling cascades. Thus, Rho GTPases represent points of signaling convergence as well as relay switches that disseminate signaling divergence. In this review, we highlight issues relating to the structural basis by which Dbl family GEFs facilitate signaling convergence and Rho GTPase activation, and how Rho GTPases promote signal dissemination through downstream effectors.
The role of Rho GTPases in disease development
Gene, 2002
The functionality and efficacy of Rho GTPase signaling is pivotal for a plethora of biological processes. Due to the integral nature of these molecules, the dysregulation of their activities can result in diverse aberrant phenotypes. Dysregulation can, as will be described below, be based on an altered signaling strength on the level of a specific regulator or that of the respective GTPase itself. Alternatively, effector pathways emanating from a specific Rho GTPase may be under-or overactivated. In this review, we address the role of the Rho-type GTPases as a subfamily of the Ras-superfamily of small GTP-binding proteins in the development of various disease phenotypes. The steadily growing list of genetic alterations that specifically impinge on proper Rho GTPase function corresponds to pathological categories such as cancer progression, mental disabilities and a group of quite diverse and unrelated disorders. We will provide an overview of diseaserendering mutations in genes that have been positively correlated with Rho GTPase signaling and will discuss the cellular and molecular mechanisms that may be affected by them. q
Spatial Organization of Rho GTPase signaling by RhoGEF/RhoGAP proteins
2018
Rho GTPases control cell morphogenesis and thus fundamental processes in all eukaryotes. They are regulated by 145 RhoGEF and RhoGAP multi-domain proteins in humans. How the Rho signaling system is organized to generate localized responses in cells and prevent their spreading is not understood. Here, we systematically characterized the substrate specificities, localization and interactome of the RhoGEFs/RhoGAPs and revealed their critical role in contextualizing and spatially delimiting Rho signaling. They localize to multiple compartments providing positional information, are extensively interconnected to jointly coordinate their signaling networks and are widely autoinhibited to remain sensitive to local activation. RhoGAPs exhibit lower substrate specificity than RhoGEFs and may contribute to preserving Rho activity gradients. Our approach led us to uncover a multi-RhoGEF complex downstream of G-protein-coupled receptors controlling a Cdc42/RhoA crosstalk. The spatial organizatio...
Uncovering the secret life of Rho GTPases
eLife
New methods to directly visualize Rho GTPases reveal how a protein called RhoGDI regulates the activity of these 'molecular switches' at the plasma membrane.