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  • ROP GTPases act with the receptor-like protein PAN1 to polarize asymmetric cell division in maize. 21653193

    Plant Rho family GTPases (ROPs) have been investigated primarily for their functions in polarized cell growth. We previously showed that the maize (Zea mays) Leu-rich repeat receptor-like protein PANGLOSS1 (PAN1) promotes the polarization of asymmetric subsidiary mother cell (SMC) divisions during stomatal development. Here, we show that maize Type I ROPs 2 and 9 function together with PAN1 in this process. Partial loss of ROP2/9 function causes a weak SMC division polarity phenotype and strongly enhances this phenotype in pan1 mutants. Like PAN1, ROPs accumulate in an asymmetric manner in SMCs. Overexpression of yellow fluorescent protein-ROP2 is associated with its delocalization in SMCs and with aberrantly oriented SMC divisions. Polarized localization of ROPs depends on PAN1, but PAN1 localization is insensitive to depletion and depolarization of ROP. Membrane-associated Type I ROPs display increased nonionic detergent solubility in pan1 mutants, suggesting a role for PAN1 in membrane partitioning of ROPs. Finally, endogenous PAN1 and ROP proteins are physically associated with each other in maize tissue extracts, as demonstrated by reciprocal coimmunoprecipitation experiments. This study demonstrates that ROPs play a key role in polarization of plant cell division and cell growth and reveals a role for a receptor-like protein in spatial localization of ROPs.
    Document Type:
    Reference
    Product Catalog Number:
    MAB1501R
    Product Catalog Name:
    Anti-Actin Antibody,clone C4

  • RAL GTPases are linchpin modulators of human tumour-cell proliferation and survival. 12856001

    The monomeric RAL (RAS-like) GTPases have been indirectly implicated in mitogenic regulation and cell transformation. Here, we show that RALA and RALB collaborate to maintain tumorigenicity through regulation of both proliferation and survival. Remarkably, this task is divided between these highly homologous isoforms. RALB is specifically required for survival of tumour cells but not normal cells. RALA is dispensable for survival, but is required for anchorage-independent proliferation. Reducing the 'oncogenic burden' in human tumour cells relieves the sensitivity to loss of RALB. These observations establish RAL GTPases as crucial components of the cellular machinery that are exploited by factors that drive oncogenic transformation.
    Document Type:
    Reference
    Product Catalog Number:
    04-037
    Product Catalog Name:
    Anti-RalB Antibody, clone 25

  • p47 GTPases regulate Toxoplasma gondii survival in activated macrophages. 15908352

    The cytokine gamma interferon (IFN-gamma) is critical for resistance to Toxoplasma gondii. IFN-gamma strongly activates macrophages and nonphagocytic host cells to limit intracellular growth of T. gondii; however, the cellular factors that are required for this effect are largely unknown. We have shown previously that IGTP and LRG-47, members of the IFN-gamma-regulated family of p47 GTPases, are required for resistance to acute T. gondii infections in vivo. In contrast, IRG-47, another member of this family, is not required. In the present work, we addressed whether these GTPases are required for IFN-gamma-induced suppression of T. gondii growth in macrophages in vitro. Bone marrow macrophages that lacked IGTP or LRG-47 displayed greatly attenuated IFN-gamma-induced inhibition of T. gondii growth, while macrophages that lacked IRG-47 displayed normal inhibition. Thus, the ability of the p47 GTPases to limit acute infection in vivo correlated with their ability to suppress intracellular growth in macrophages in vitro. Using confocal microscopy and sucrose density fractionation, we demonstrated that IGTP largely colocalizes with endoplasmic reticulum markers, while LRG-47 was mainly restricted to the Golgi. Although both IGTP and LRG-47 localized to vacuoles containing latex beads, neither protein localized to vacuoles containing live T. gondii. These results suggest that IGTP and LRG-47 are able to regulate host resistance to acute T. gondii infections through their ability to inhibit parasite growth within the macrophage.
    Document Type:
    Reference
    Product Catalog Number:
    Multiple
    Product Catalog Name:
    Multiple

  • Ral GTPases regulate exocyst assembly through dual subunit interactions. 14525976

    Ral GTPases have been implicated in the regulation of a variety of dynamic cellular processes including proliferation, oncogenic transformation, actin-cytoskeletal dynamics, endocytosis, and exocytosis. Recently the Sec6/8 complex, or exocyst, a multisubunit complex facilitating post-Golgi targeting of distinct subclasses of secretory vesicles, has been identified as a bona fide Ral effector complex. Ral GTPases regulate exocyst-dependent vesicle trafficking and are required for exocyst complex assembly. Sec5, a membrane-associated exocyst subunit, has been identified as a direct target of activated Ral; however, the mechanism by which Ral can modulate exocyst assembly is unknown. Here we report that an additional component of the exocyst, Exo84, is a direct target of activated Ral. We provide evidence that mammalian exocyst components are present as distinct subcomplexes on vesicles and the plasma membrane and that Ral GTPases regulate the assembly interface of a full octameric exocyst complex through interaction with Sec5 and Exo84.
    Document Type:
    Reference
    Product Catalog Number:
    05-369
    Product Catalog Name:
    Anti-Na+/K+ ATPase α-1 Antibody, clone C464.6

  • GTPases and T cell activation. 12670400

    Guanine nucleotide binding proteins rapidly cycle between a guanosine diphosphate (GDP)-bound and guanosine triphosphate (GTP)-bound state, and they operate as binary switches that control cell activation in response to environmental cues. GTPases adopt different conformations when binding GTP vs. GDP. The GTP-bound state is generally considered to be the active conformation that allows GTPases to interact with downstream effectors and thereby initiate downstream signaling pathways, which regulate many important biological processes. Many members of the Ras family of GTPases, notably Ras and Rap1A, and the Rho family GTPases, Cdc42Hs, Rac1, Rac2 and RhoA, are important components of signal transduction pathways used by antigen receptors, costimulatory, cytokine and chemokine receptors to regulate the immune response. This review discusses current knowledge and ideas about the regulation and function of these GTPases in lymphocytes.
    Document Type:
    Reference
    Product Catalog Number:
    07-604

  • Atlastin GTPases are required for Golgi apparatus and ER morphogenesis. 18270207

    The hereditary spastic paraplegias (SPG1-33) comprise a cluster of inherited neurological disorders characterized principally by lower extremity spasticity and weakness due to a length-dependent, retrograde axonopathy of corticospinal motor neurons. Mutations in the gene encoding the large oligomeric GTPase atlastin-1 are responsible for SPG3A, a common autosomal dominant hereditary spastic paraplegia. Here we describe a family of human GTPases, atlastin-2 and -3 that are closely related to atlastin-1. Interestingly, while atlastin-1 is predominantly localized to vesicular tubular complexes and cis-Golgi cisternae, mostly in brain, atlastin-2 and -3 are localized to the endoplasmic reticulum (ER) and are most enriched in other tissues. Knockdown of atlastin-2 and -3 levels in HeLa cells using siRNA (small interfering RNA) causes disruption of Golgi morphology, and these Golgi structures remain sensitive to brefeldin A treatment. Interestingly, expression of SPG3A mutant or dominant-negative atlastin proteins lacking GTPase activity causes prominent inhibition of ER reticularization, suggesting a role for atlastin GTPases in the formation of three-way junctions in the ER. However, secretory pathway trafficking as assessed using vesicular stomatitis virus G protein fused to green fluorescent protein (VSVG-GFP) as a reporter was essentially normal in both knockdown and dominant-negative overexpression conditions for all atlastins. Thus, the atlastin family of GTPases functions prominently in both ER and Golgi morphogenesis, but they do not appear to be required generally for anterograde ER-to-Golgi trafficking. Abnormal morphogenesis of the ER and Golgi resulting from mutations in atlastin-1 may ultimately underlie SPG3A by interfering with proper membrane distribution or polarity of the long corticospinal motor neurons.
    Document Type:
    Reference
    Product Catalog Number:
    05-163
    Product Catalog Name:
    Anti-PLCγ-1 Antibody

  • Cdc42 and Rac family GTPases regulate mode and speed but not direction of primary fibroblast migration during platelet-derived growth factor-dependent chemotaxis. 19273601

    Cdc42 and Rac family GTPases are important regulators of morphology, motility, and polarity in a variety of mammalian cell types. However, comprehensive analysis of their roles in the morphological and behavioral aspects of chemotaxis within a single experimental system is still lacking. Here we demonstrate using a direct viewing chemotaxis assay that of all of the Cdc42/Rac1-related GTPases expressed in primary fibroblasts, Cdc42, Rac1, and RhoG are required for efficient migration towards platelet-derived growth factor (PDGF). During migration, Cdc42-, Rac1-, and RhoG-deficient cells show aberrant morphology characterized as cell elongation and cell body rounding, loss of lamellipodia, and formation of thick membrane extensions, respectively. Analysis of individual cell trajectories reveals that cell speed is significantly reduced, as well as persistence, but to a smaller degree, while the directional response to the gradient of PDGF is not affected. Combined knockdown of Cdc42, Rac1, and RhoG results in greater inhibition of cell speed than when each protein is knocked down alone, but the cells are still capable of migrating toward PDGF. We conclude that, Cdc42, Rac1, and RhoG function cooperatively during cell migration and that, while each GTPase is implicated in the control of morphology and cell speed, these and other Cdc42/Rac-related GTPases are not essential for the directional response toward PDGF.
    Document Type:
    Reference
    Product Catalog Number:
    07-604

  • Rad and Rad-related GTPases interact with calmodulin and calmodulin-dependent protein kinase II. 9115241

    Members of the Rad family of GTPases (including Rad, Gem, and Kir) possess several unique features of unknown function in comparison to other Ras-like proteins, with major N-terminal and C-terminal extensions, a lack of typical prenylation motifs, and several non-conservative changes in the sequence of the GTP binding domain. Here we show that Rad and Gem bind to calmodulin (CaM)-Sepharose in vitro in a calcium-dependent manner and that Rad can be co-immunoprecipitated with CaM in C2C12 cells. The interaction is influenced by the guanine nucleotide binding state of Rad with the GDP-bound form exhibiting 5-fold better binding to CaM than the GTP-bound protein. In addition, the dominant negative mutant of Rad (S105N) which binds GDP, but not GTP, exhibits enhanced binding to CaM in vivo when expressed in C2C12 cells. Peptide competition studies and expression of deletion mutants of Rad localize the binding site for CaM to residues 278-297 at the C terminus of Rad. This domain contains a motif characteristic of a calmodulin-binding region, consisting of numerous basic and hydrophobic residues. In addition, we have identified a second potential regulatory domain in the extended N terminus of Rad which, when removed, decreases Rad protein expression but increases the binding of Rad to CaM. The ability of Rad mutants to bind CaM correlates with their localization in cytoskeletal fractions of C2C12 cells. Immunoprecipitates of calmodulin-dependent protein kinase II, the cellular effector of Ca2+-calmodulin, also contain Rad, and in vitro both Rad and Gem can serve as substrates for this kinase. Thus, the Rad family of GTP-binding proteins possess unique characteristics of binding CaM and calmodulin-dependent protein kinase II, suggesting a role for Rad-like GTPases in calcium activation of serine/threonine kinase cascades.
    Document Type:
    Reference
    Product Catalog Number:
    05-173
    Product Catalog Name:
    Anti-Calmodulin Antibody