The Many Faces of Rap1 GTPase

This review addresses the issue of the numerous roles played by Rap1 GTPase (guanosine triphosphatase) in different cell types, in terms of both physiology and pathology. It is one among a myriad of small G proteins with endogenous GTP-hydrolyzing activity that is considerably stimulated by posttranslational modifications (geranylgeranylation) or guanine nucleotide exchange factors (GEFs), and inhibited by GTPase-activating proteins (GAPs). Rap1 is a ubiquitous protein that plays an essential role in the control of metabolic processes, such as signal transduction from plasma membrane receptors, cytoskeleton rearrangements necessary for cell division, intracellular and substratum adhesion, as well as cell motility, which is needed for extravasation or fusion. We present several examples of how Rap1 affects cells and organs, pointing to possible molecular manipulations that could have application in the therapy of several diseases.

Download Full-text

Structural and Spatial Determinants Regulating TC21 Activation by RasGRF Family Nucleotide Exchange Factors

Molecular Biology of the Cell ◽

10.1091/mbc.e09-03-0212 ◽

2009 ◽

Vol 20 (20) ◽

pp. 4289-4302 ◽

Cited By ~ 10

Author(s):

Fernando Calvo ◽

Piero Crespo

Keyword(s):

Posttranslational Modifications ◽

Guanine Nucleotide Exchange Factors ◽

Guanine Nucleotide ◽

Nucleotide Exchange ◽

Guanosine Triphosphate ◽

Guanosine Diphosphate ◽

Ras Gtpases ◽

Guanine Nucleotide Exchange ◽

Nucleotide Exchange Factors ◽

Exchange Activity

RasGRF family guanine nucleotide exchange factors (GEFs) promote guanosine diphosphate (GDP)/guanosine triphosphate (GTP) exchange on several Ras GTPases, including H-Ras and TC21. Although the mechanisms controlling RasGRF function as an H-Ras exchange factor are relatively well characterized, little is known about how TC21 activation is regulated. Here, we have studied the structural and spatial requirements involved in RasGRF 1/2 exchange activity on TC21. We show that RasGRF GEFs can activate TC21 in all of its sublocalizations except at the Golgi complex. We also demonstrate that TC21 susceptibility to activation by RasGRF GEFs depends on its posttranslational modifications: farnesylated TC21 can be activated by both RasGRF1 and RasGRF2, whereas geranylgeranylated TC21 is unresponsive to RasGRF2. Importantly, we show that RasGRF GEFs ability to catalyze exchange on farnesylated TC21 resides in its pleckstrin homology 1 domain, by a mechanism independent of localization and of its ability to associate to membranes. Finally, our data indicate that Cdc42-GDP can inhibit TC21 activation by RasGRF GEFs, demonstrating that Cdc42 negatively affects the functions of RasGRF GEFs irrespective of the GTPase being targeted.

Download Full-text

Focus on Cdc42 in Breast Cancer: New Insights, Target Therapy Development and Non-Coding RNAs

Cells ◽

10.3390/cells8020146 ◽

2019 ◽

Vol 8 (2) ◽

pp. 146 ◽

Cited By ~ 11

Author(s):

Yu Zhang ◽

Jun Li ◽

Xing-Ning Lai ◽

Xue-Qiao Jiao ◽

Jun-Ping Xiong ◽

...

Keyword(s):

Breast Cancer ◽

Malignant Tumors ◽

Target Therapy ◽

Nucleotide Exchange ◽

Surface Receptors ◽

Cellular Processes ◽

Guanine Nucleotide Exchange ◽

Nucleotide Exchange Factors ◽

Non Coding Rnas ◽

Guanosine Triphosphatase

Breast cancer is the most common malignant tumors in females. Although the conventional treatment has demonstrated a certain effect, some limitations still exist. The Rho guanosine triphosphatase (GTPase) Cdc42 (Cell division control protein 42 homolog) is often upregulated by some cell surface receptors and oncogenes in breast cancer. Cdc42 switches from inactive guanosine diphosphate (GDP)-bound to active GTP-bound though guanine-nucleotide-exchange factors (GEFs), results in activation of signaling cascades that regulate various cellular processes such as cytoskeletal changes, proliferation and polarity establishment. Targeting Cdc42 also provides a strategy for precise breast cancer therapy. In addition, Cdc42 is a potential target for several types of non-coding RNAs including microRNAs and lncRNAs. These non-coding RNAs is extensively involved in Cdc42-induced tumor processes, while many of them are aberrantly expressed. Here, we focus on the role of Cdc42 in cell morphogenesis, proliferation, motility, angiogenesis and survival, introduce the Cdc42-targeted non-coding RNAs, as well as present current development of effective Cdc42-targeted inhibitors in breast cancer.

Download Full-text

The Rho-GEF PIX-1 directs assembly or stability of lateral attachment structures between muscle cells

Nature Communications ◽

10.1038/s41467-020-18852-4 ◽

2020 ◽

Vol 11 (1) ◽

Author(s):

Jasmine C. Moody ◽

Hiroshi Qadota ◽

April R. Reedy ◽

C. Denise Okafor ◽

Niveda Shanmugan ◽

...

Keyword(s):

Muscle Cell ◽

Muscle Cells ◽

Cell Types ◽

Nucleotide Exchange ◽

C Elegans ◽

Guanine Nucleotide Exchange ◽

Nucleotide Exchange Factors ◽

Attachment Structures ◽

Genes Encoding ◽

Rho Gef

Abstract PIX proteins are guanine nucleotide exchange factors (GEFs) that activate Rac and Cdc42, and are known to have numerous functions in various cell types. Here, we show that a PIX protein has an important function in muscle. From a genetic screen in C. elegans, we found that pix-1 is required for the assembly of integrin adhesion complexes (IACs) at borders between muscle cells, and is required for locomotion of the animal. A pix-1 null mutant has a reduced level of activated Rac in muscle. PIX-1 localizes to IACs at muscle cell boundaries, M-lines and dense bodies. Mutations in genes encoding proteins at known steps of the PIX signaling pathway show defects at muscle cell boundaries. A missense mutation in a highly conserved residue in the RacGEF domain results in normal levels of PIX-1 protein, but a reduced level of activated Rac in muscle, and abnormal IACs at muscle cell boundaries.

Download Full-text

Mechanisms and consequences of dysregulation of the Tiam family of Rac activators in disease

Biochemical Society Transactions ◽

10.1042/bst20200481 ◽

2020 ◽

Vol 48 (6) ◽

pp. 2703-2719

Author(s):

Joe Maltas ◽

Hannah Reed ◽

Andrew Porter ◽

Angeliki Malliri

Keyword(s):

Neurological Disorders ◽

Cell Types ◽

Guanine Nucleotide Exchange Factors ◽

Cellular Migration ◽

Subcellular Localisation ◽

Nucleotide Exchange ◽

Guanine Nucleotide Exchange ◽

Nucleotide Exchange Factors ◽

And Function ◽

Compare And Contrast

The Tiam family proteins — Tiam1 and Tiam2/STEF — are Rac1-specific Guanine Nucleotide Exchange Factors (GEFs) with important functions in epithelial, neuronal, immune and other cell types. Tiam GEFs regulate cellular migration, proliferation and survival, mainly through activating and directing Rac1 signalling. Dysregulation of the Tiam GEFs is significantly associated with human diseases including cancer, immunological and neurological disorders. Uncovering the mechanisms and consequences of dysregulation is therefore imperative to improving the diagnosis and treatment of diseases. Here we compare and contrast the subcellular localisation and function of Tiam1 and Tiam2/STEF, and review the evidence for their dysregulation in disease.

Download Full-text

Rap1 promotes cell spreading by localizing Rac guanine nucleotide exchange factors

The Journal of Cell Biology ◽

10.1083/jcb.200404068 ◽

2004 ◽

Vol 167 (1) ◽

pp. 111-122 ◽

Cited By ~ 191

Author(s):

William T. Arthur ◽

Lawrence A. Quilliam ◽

Jonathan A. Cooper

Keyword(s):

Cell Spreading ◽

Cell Types ◽

Guanine Nucleotide Exchange Factors ◽

Cell Periphery ◽

Guanine Nucleotide ◽

Nucleotide Exchange ◽

Subcellular Targeting ◽

Guanine Nucleotide Exchange ◽

Nucleotide Exchange Factors ◽

Membrane Protrusions

The Ras-related GTPase Rap1 stimulates integrin-mediated adhesion and spreading in various mammalian cell types. Here, we demonstrate that Rap1 regulates cell spreading by localizing guanine nucleotide exchange factors (GEFs) that act via the Rho family GTPase Rac1. Rap1a activates Rac1 and requires Rac1 to enhance spreading, whereas Rac1 induces spreading independently of Rap1. Active Rap1a binds to a subset of Rac GEFs, including VAV2 and Tiam1 but not others such as SWAP-70 or COOL-1. Overexpressed VAV2 and Tiam1 specifically require Rap1 to promote spreading, even though Rac1 is activated independently of Rap1. Rap1 is necessary for the accumulation of VAV2 in membrane protrusions at the cell periphery. In addition, if VAV2 is artificially localized to the cell edge with the subcellular targeting domain of Rap1a, it increases cell spreading independently of Rap1. These results lead us to propose that Rap1 promotes cell spreading by localizing a subset of Rac GEFs to sites of active lamellipodia extension.

Download Full-text

The Multiple Functions of Rho GTPases in Fission Yeasts

Cells ◽

10.3390/cells10061422 ◽

2021 ◽

Vol 10 (6) ◽

pp. 1422

Author(s):

Jero Vicente-Soler ◽

Teresa Soto ◽

Alejandro Franco ◽

José Cansado ◽

Marisa Madrid

Keyword(s):

Fission Yeast ◽

Rho Gtpases ◽

Current Knowledge ◽

Model Organism ◽

Nucleotide Exchange ◽

Guanine Nucleotide Exchange ◽

Nucleotide Exchange Factors ◽

Physiological Processes ◽

Evolutionary Changes ◽

Rho Family

The Rho family of GTPases represents highly conserved molecular switches involved in a plethora of physiological processes. Fission yeast Schizosaccharomyces pombe has become a fundamental model organism to study the functions of Rho GTPases over the past few decades. In recent years, another fission yeast species, Schizosaccharomyces japonicus, has come into focus offering insight into evolutionary changes within the genus. Both fission yeasts contain only six Rho-type GTPases that are spatiotemporally controlled by multiple guanine–nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs), and whose intricate regulation in response to external cues is starting to be uncovered. In the present review, we will outline and discuss the current knowledge and recent advances on how the fission yeasts Rho family GTPases regulate essential physiological processes such as morphogenesis and polarity, cellular integrity, cytokinesis and cellular differentiation.

Download Full-text

Concentration of Sec12 at ER exit sites via interaction with cTAGE5 is required for collagen export

The Journal of Cell Biology ◽

10.1083/jcb.201312062 ◽

2014 ◽

Vol 206 (6) ◽

pp. 751-762 ◽

Cited By ~ 66

Author(s):

Kota Saito ◽

Koh Yamashiro ◽

Noriko Shimazu ◽

Tomoya Tanabe ◽

Kenji Kontani ◽

...

Keyword(s):

Direct Interaction ◽

Secretory Proteins ◽

Nucleotide Exchange ◽

Guanine Nucleotide Exchange ◽

Transport Vesicles ◽

Nucleotide Exchange Factor ◽

Receptor Component ◽

Er Exit Sites ◽

Guanosine Triphosphatase ◽

Trimeric Structure

Mechanisms for exporting variably sized cargo from the endoplasmic reticulum (ER) using the same machinery remain poorly understood. COPII-coated vesicles, which transport secretory proteins from the ER to the Golgi apparatus, are typically 60–90 nm in diameter. However, collagen, which forms a trimeric structure that is too large to be accommodated by conventional transport vesicles, is also known to be secreted via a COPII-dependent process. In this paper, we show that Sec12, a guanine-nucleotide exchange factor for Sar1 guanosine triphosphatase, is concentrated at ER exit sites and that this concentration of Sec12 is specifically required for the secretion of collagen VII but not other proteins. Furthermore, Sec12 recruitment to ER exit sites is organized by its direct interaction with cTAGE5, a previously characterized collagen cargo receptor component, which functions together with TANGO1 at ER exit sites. These findings suggest that the export of large cargo requires high levels of guanosine triphosphate–bound Sar1 generated by Sec12 localized at ER exit sites.

Download Full-text

Involvement of the Switch 2 Domain of Ras in Its Interaction with Guanine Nucleotide Exchange Factors

Journal of Biological Chemistry ◽

10.1074/jbc.271.19.11076 ◽

1996 ◽

Vol 271 (19) ◽

pp. 11076-11082 ◽

Cited By ~ 33

Author(s):

Lawrence A. Quilliam ◽

Mark M. Hisaka ◽

Sheng Zhong ◽

Amy Lowry ◽

Raymond D. Mosteller ◽

...

Keyword(s):

Guanine Nucleotide Exchange Factors ◽

Guanine Nucleotide ◽

Nucleotide Exchange ◽

Guanine Nucleotide Exchange ◽

Nucleotide Exchange Factors

Download Full-text

Essential Role of Vav Family Guanine Nucleotide Exchange Factors in EphA Receptor-Mediated Angiogenesis

Molecular and Cellular Biology ◽

10.1128/mcb.02215-05 ◽

2006 ◽

Vol 26 (13) ◽

pp. 4830-4842 ◽

Cited By ~ 84

Author(s):

Sonja G. Hunter ◽

Guanglei Zhuang ◽

Dana Brantley-Sieders ◽

Wojciech Swat ◽

Christopher W. Cowan ◽

...

Keyword(s):

Guanine Nucleotide Exchange Factors ◽

Guanine Nucleotide ◽

Nucleotide Exchange ◽

Guanine Nucleotide Exchange ◽

Nucleotide Exchange Factors ◽

Rac1 Gtpase ◽

Rho Family ◽

Epha Receptor

ABSTRACT Angiogenesis, the process by which new blood vessels are formed from preexisting vasculature, is critical for vascular remodeling during development and contributes to the pathogenesis of diseases such as cancer. Prior studies from our laboratory demonstrate that the EphA2 receptor tyrosine kinase is a key regulator of angiogenesis in vivo. The EphA receptor-mediated angiogenic response is dependent on activation of Rho family GTPase Rac1 and is regulated by phosphatidylinositol 3-kinase. Here we report the identification of Vav2 and Vav3 as guanine nucleotide exchange factors (GEFs) that link the EphA2 receptor to Rho family GTPase activation and angiogenesis. Ephrin-A1 stimulation recruits the binding of Vav proteins to the activated EphA2 receptor. The induced association of EphA receptor and Vav proteins modulates the activity of Vav GEFs, leading to activation of Rac1 GTPase. Overexpression of either Vav2 or Vav3 in primary microvascular endothelial cells promotes Rac1 activation, cell migration, and assembly in response to ephrin-A1 stimulation. Conversely, loss of Vav2 and Vav3 GEFs inhibits Rac1 activation and ephrin-A1-induced angiogenic responses both in vitro and in vivo. In addition, embryonic fibroblasts derived from Vav2−/− Vav3−/− mice fail to spread on an ephrin-A1-coated surface and exhibit a significant decrease in the formation of ephrin-A1-induced lamellipodia and filopodia. These findings suggest that Vav GEFs serve as a molecular link between EphA2 receptors and the actin cytoskeleton and provide an important mechanism for EphA2-mediated angiogenesis.

Download Full-text