The Rho GDI Rdi1 regulates Rho GTPases by distinct mechanisms

© 2008 by The American Society for Cell Biology. Under the License and Publishing Agreement, authors grant to the general public, effective two months after publication of (i.e.,. the appearance of) the edited manuscript in an online issue of MBoC, the nonexclusive right to copy, distribute, or display the manuscript subject to the terms of the Creative Commons–Noncommercial–Share Alike 3.0 Unported license (http://creativecommons.org/licenses/by-nc-sa/3.0).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 3β homologue Ygk3, vacuolar proteases, and the proteasome. Together, these results indicate that Rdi1 uses distinct modes of regulation for different Rho GTPases.Deutsche Forschungsgemeinschaf

Untersuchungen zur trockenen Deposition und Emission von atmosphärischem NO, NO2_{2} und HNO3_{3} an natürlichen Oberflächen

Emission and dry deposition of the atmospheric nitrogen oxides NO, NO$_{2}$ and HNO$_{3}$ from and to vegetated and base soils and a natural water surface were determined in numerous laboratory and field experiments. The influence of soil temperature, soil water content and atmospheric mixing ratio of the respective nitrogen oxide on its exchange at the soil-air-boundary was evaluated in the laboratory by means of the dynamic chamber method. These parameters showed to be of tremendous importance for amount and direction of the flux of nitroen oxides. Main result in discussing the field experiments was that emission and deposition of NO and NO$_{2}$ exist simultaneously. The veritcal flux of NO and NO$_{2}$ was a coupling of two parts - directed from the atmosphere to the soil and vice versa at the same time. Resulting net fluxes of up to $\pm$ 10$^{3} \mu g n^{-2}h^{-1}$ were found, depending on atmospheric and soil parameters. This explains the large variance of NO and NO$_{2}$ deposition velocity values found in the literature. In the case of HNO$_{3}$ only deposition was found. Deposition velocities ranged from 0.4 to 0.8 cm s$^{-1}$ (base soil and lake water surface) up to 6 cm s$^{-1}$ (soil with sugar beets) independent of temperáture and soil water content. Many additional field experiments with the gradient method and the chamber method supported the results of the laboratory experiments