The Rho GTPase Rho3 Has a Direct Role in Exocytosis That Is Distinct from Its Role in Actin Polarity

Department of Cell Biology, Cell Biology, and Genetics, Weill Medical College of Cornell University, New York, New York 10021, USA.
Molecular Biology of the Cell (Impact Factor: 4.47). 01/2000; 10(12):4121-33. DOI: 10.1091/mbc.10.12.4121
Source: PubMed


Budding yeast grow asymmetrically by the polarized delivery of proteins and lipids to specific sites on the plasma membrane. This requires the coordinated polarization of the actin cytoskeleton and the secretory apparatus. We identified Rho3 on the basis of its genetic interactions with several late-acting secretory genes. Mutational analysis of the Rho3 effector domain reveals three distinct functions in cell polarity: regulation of actin polarity, transport of exocytic vesicles from the mother cell to the bud, and docking and fusion of vesicles with the plasma membrane. We provide evidence that the vesicle delivery function of Rho3 is mediated by the unconventional myosin Myo2 and that the docking and fusion function is mediated by the exocyst component Exo70. These data suggest that Rho3 acts as a key regulator of cell polarity and exocytosis, coordinating several distinct events for delivery of proteins to specific sites on the cell surface.

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Available from: Patrick J Brennwald, Dec 21, 2014
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    • "Rho3, one monomeric GTPase of the Rho superfamily, is found only in fungi. Rho3 was first isolated in Sacchoromyces cerevisiae, and subsequently shown to modulate vesicle delivery, cell growth, cell polarity, cell division, exocytosis, and vesicle secretion in yeast (Adamo et al., 1999; Nakano et al., 2002; Wu et al., 2010). Rho3 have specific functions in different filamentous fungi. "
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    ABSTRACT: Small GTPases of the Rho family play an important role in regulating biological processes in fungi. In this study, we mainly investigated the biological functions of Rho3 in Botrytis cinerea, and found that deletion of the rho3 from B. cinerea significantly suppressed vegetative growth and conidiation, reduced appressorium formation and decreased virulence. Microscopy analysis revealed that the distance between septa was increased in the Δrho3 mutant. In addition, mitochondria were suggested to be the main sources of intracellular reactive oxygen species (ROS) in B. cinerea based on dual staining with 2’, 7’-dichlorodihydrofluorescein diacetate and MitoTracker orange. The Δrho3 mutant showed less accumulation of ROS in the hyphae tips compared to the WT strain of B. cinerea. These results provide the novel evidence to ascertain the function of small GTPase Rho3 in regulating growth, conidiation and virulence of B. cinerea.
    Fungal Genetics and Biology 01/2015; 75. DOI:10.1016/j.fgb.2015.01.007 · 2.59 Impact Factor
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    • "In budding yeast, cell polarity and polarized exocytosis is coordinated also by the Rho3p GTPase (Adamo et al., 1999), which can regulate both actin polarity and transport of exocytic vesicles from mother cell to the bud, as well as vesicle docking to the PM. While the Rho3p vesicle delivery function is mediated by Myo2p, the docking requires Exo70p (Adamo et al., 1999). "
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    ABSTRACT: Delivery and final fusion of the secretory vesicles with the relevant target membrane are hierarchically organized and reciprocally interconnected multi-step processes involving not only specific protein-protein interactions, but also specific protein-phospholipid interactions. The exocyst was discovered as a tethering complex mediating initial encounter of arriving exocytic vesicles with the plasma membrane. The exocyst complex is regulated by Rab and Rho small GTPases, resulting in docking of exocytic vesicles to the plasma membrane (PM) and finally their fusion mediated by specific SNARE complexes. In model Opisthokont cells, the exocyst was shown to directly interact with both microtubule and microfilament cytoskeleton and related motor proteins as well as with the PM via phosphatidylinositol 4, 5-bisphosphate specific binding, which directly affects cortical cytoskeleton and PM dynamics. Here we summarize the current knowledge on exocyst-cytoskeleton-PM interactions in order to open a perspective for future research in this area in plant cells.
    Frontiers in Plant Science 01/2014; 4:543. DOI:10.3389/fpls.2013.00543 · 3.95 Impact Factor
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    • "In the yeast Saccharomyces cerevisiae six Rho GTPases (Cdc42p and Rho1p-Rho5p) were described to be mainly involved in cell polarity. Among them, Rho3p and Rho4p are involved in the establishment of cell polarity in yeast at the bud tip and bud neck respectively [5] [6] [7] [8]. Biological activity of Rho proteins is negatively controlled by RhoGTPase-Activating Proteins (RhoGAPs) [9]. "
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    ABSTRACT: Polarized growth of the yeast Saccharomyces cerevisiae depends on different biological processes and requires several signaling pathways. Signaling is mediated through a set of proteins, which include Rho3p and Rho4p GTPases. Although these two proteins are involved in the control of distinct aspects of polarized growth in yeast, they have a common regulator: the Rgd1 RhoGAP protein. Here we demonstrate that Rgd1p is phosphorylated by the Aurora B like kinase Ipl1 and we observe that loss of Ipl1 function leads to a new Rgd1p distribution in a small part of the cell population.
    Biochemical and Biophysical Research Communications 02/2013; 433(1). DOI:10.1016/j.bbrc.2013.02.081 · 2.30 Impact Factor
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