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

Coordination Complexes of Transition Metals (M = Mo, Fe, Rh, and Ru) with Tin(II) Phthalocyanine in Neutral, Monoanionic, and Dianionic States

The ability of tin atoms to form stable Sn–M bonds with transition metals was used to prepare transition metal complexes with tin­(II) phthalocyanine in neutral, monoanionic, and dianionic states. These complexes were obtained via the interactions of [Sn^IVCl₂Pc­(3−)]^•– or [Sn^IIPc­(3−)]^•– radical anions with {Cp*Mo­(CO)₂}₂, {CpFe­(CO)₂}₂, {CpMo­(CO)₃}₂, Fe₃(CO)₁₂, {Cp*RhCl₂}₂, or Ph₅CpRu­(CO)₂Cl. The neutral coordination complexes of Cp*MoBr­(CO)₂[Sn^IIPc­(2−)]·0.5C₆H₄Cl₂ (<b>1</b>) and CpFe­(CO)₂[Sn^IIPc­(2−)]·2C₆H₄Cl₂ (<b>2</b>) were obtained from [Sn^IVCl₂Pc­(3−)]^•–. On the other hand, the coordination of transition metals to [Sn^IIPc­(3−)]^•– yielded anionic coordination complexes preserving the spin on [Sn^IIPc­(3−)]^•–. However, in the case of {cryptand­[2,2,2]­(Na⁺)}­{CpFe^II(CO)₂[Sn^IIPc­(4−)]}⁻·C₆H₄Cl₂ (<b>4</b>), charge transfer from CpFe^I(CO)₂ to [Sn^IIPc­(3−)]^•– took place to form the diamagnetic [Sn^IIPc­(4−)]^2– dianion and {CpFe^II(CO)₂}⁺. The complexes {cryptand­[2,2,2]­(Na⁺)}­{Fe­(CO)₄[Sn^IIPc­(3−)]^•–} (<b>5</b>), {cryptand­[2,2,2]­(Na⁺)}­{CpMo­(CO)₂[Sn^IIPc­(2−)­Sn^IIPc­(3−)^•–]} (<b>6</b>), and {cryptand­[2,2,2]­(Na⁺)}­{Cp*RhCl₂[Sn^IIPc­(3−)]^•–} (<b>7</b>) have magnetic moments of 1.75, 2.41, and 1.75 μ_B, respectively, owing to the presence of <i>S</i> = 1/2 spins on [Sn^IIPc­(3−)]^•– and CpMo^I(CO)₂ (for <b>6</b>). In addition, the strong antiferromagnetic coupling of spins with Weiss temperatures of −35.5 −28.6 K was realized between the CpMo^I(CO)₂ and the [Sn^IIPc­(3−)]^•– units in <b>6</b> and the π-stacking {Fe­(CO)₄[Sn^IIPc­(3−)]^•–}₂ dimers of <b>5</b>, respectively. The [Sn^IIPc­(3−)]^•– radical anions substituted the chloride anions in Ph₅CpRu­(CO)₂Cl to form the formally neutral compound {Ph₅CpRu^II(CO)₂[Sn^IIPc­(3−)]} (<b>8</b>) in which the negative charge and spin are preserved on [Sn^IIPc­(3−)]^•–. The strong antiferromagnetic coupling of spins with a magnetic exchange interaction <i>J/k</i>_B = −183 K in <b>8</b> is explained by the close packing of [Sn^IIPc­(3−)]^•– in the π-stacked {Ph₅CpRu^II(CO)₂[Sn^IIPc­(3−)]^•–}₂ dimers