High impact information on RHO3

• Our analysis of a Rho3 mutant that is unable to interact with the Exo70 subunit of the exocyst reveals a normal polarization of the exocyst complex as well as other polarity markers [1].
• Consistent with this model, we find that the ability of Rho3 and Cdc42 to hydrolyze GTP is not required for their role in secretion [1].
• We show that the essential function of Rho3p and Rho4p is to activate the formins Bni1p and Bnr1p, and that activated alleles of either formin are able to bypass the requirement for these Rho proteins [2].
• Extensive genetic interactions between cdc42-6 and mutations in exocytic components support this hypothesis, and indicate a functional overlap with Rho3, which also regulates both actin organization and exocytosis [3].
• Genetic analysis suggests that Sro7 and Sec9 function together in a pathway downstream of the Rho3 GTPase [4].

Biological context of RHO3

• Rho3p and Rho4p are involved in regulating cell polarity by controlling polarized exocytosis [5].
• These results demonstrate that Rho3p GTPases and Boi proteins function in the maintenance of cell polarity for bud formation [6].
• Mutational analysis revealed that the second SH3 domain from the NH2 terminus (SH3-2) of Bem1p is important for the functions of Bem1p in bud formation and in the suppression of the rho3 defect [6].
• The Rho3 protein plays a critical role in the budding yeast Saccharomyces cerevisiae by directing proper cell growth [7].
• To gain insights into how Rho3 influences these events, we have carried out a yeast two-hybrid screen using an S. cerevisiae cDNA library to identify proteins interacting with Rho3 [7].

Anatomical context of RHO3

• These results provide a direct molecular basis for the action of Rho3 on exocytosis and the actin cytoskeleton [7].
• These included alleles of CDC42 and RHO3 (cdc42-6 and rho3-V51) thought to regulate specifically the fusion of secretory vesicles but were found to affect strongly the cytoskeleton as well [8].
• Consistent with this, expression levels of RHO3 correlated with 1,6-beta-glucan levels in the cell wall [9].
• 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 [10].

Associations of RHO3 with chemical compounds

• Furthermore, the growth of T. reesei was not affected on glucose by the rho3 disruption [11].

Regulatory relationships of RHO3

• The non-essential RGD1 gene from Saccharomyces cerevisiae encodes a protein that has been characterized in vitro as a Rho GTPase activating protein (RhoGAP) for the Rho3 and Rho4 proteins [12].

Other interactions of RHO3

• Analysis of the synthetic lethal phenomenon revealed that production of activated Rho3p and Rho4p leads to lethality in wsc1Delta cells [5].
• Rgd1, a GTPase-activating protein, is the only known negative regulator of the Rho3 and Rho4 small GTPases in the yeast Saccharomyces cerevisiae [5].
• Consistent with this idea, it was found that perturbations in Rho3-mediated polarized exocytosis specifically impair the abundance and processing of Wsc1 and Mid2 proteins [5].
• Overlapping subcellular localization of the Rho3 and Exo70 proteins was demonstrated by indirect immunofluorescence [7].
• Yeast SRO7 was identified as a multicopy suppressor of a defect in Rho3p, a small GTPase that maintains cell polarity [13].

References