Cadherin adhesion molecules are believed to be important for synaptic plasticity. ␤-Catenin, which links cadherins and the actin cytoskeleton, is a modulator of cadherin adhesion and regulates synaptic structure and function. Here we show that ␤-catenin interacts with a novel GTPase-activating protein, named RICS, that acts on Cdc42 and Rac1. The RICS-␤-catenin complex was found to be associated with N-cadherin, N-methyl-D-aspartate receptors, and postsynaptic density-95, and localized to the postsynaptic density. Furthermore, the GTPase-activating protein activity of RICS was inhibited by phosphorylation by Ca 2؉ /calmodulin-dependent protein kinase II. These results suggest that RICS is involved in the synaptic adhesion-and N-methyl-D-aspartate-mediated organization of cytoskeletal networks and signal transduction. Thus, RICS may regulate dendritic spine morphology and strength by modulating Rho GTPases.Activity-induced changes in synaptic transmission efficacy, such as long term potentiation (LTP) 1 and long term depression, have been postulated to be involved in information storage during learning. Many studies have revealed that synaptic remodeling and plastic changes in dendritic spine morphology play a role in synaptic plasticity (1-6). Furthermore, changes in synaptic strength have been shown to involve the structural and functional modifications of the molecules present in the postsynaptic density (PSD) (7-10), an electrondense structure containing various structural and signaling molecules such as ion channels, scaffolding proteins, protein kinases, small G-proteins, cell adhesion proteins, and cytoskeletal proteins (11, 12).The cadherins are a family of single-pass transmembrane proteins that mediate Ca 2ϩ -dependent, homophilic intercellular adhesion (13). Some members of the cadherin family of adhesion proteins are localized to synaptic junctions and have been implicated in synaptic plasticity (14, 15). For example, inhibitory antibodies to the first extracellular domain of Ncadherin, one of the classical cadherins enriched in neural cells, have been shown to attenuate the induction of LTP (16,17). Also, antagonistic peptides containing the consensus sequence for cadherin dimer formation prevent the induction of LTP (16). Furthermore, inhibition of cadherin activity by a dominantnegative N-cadherin, as well as by mutation of ␣N-catenin, has been shown to alter dendritic spine morphology (18), suggesting that cadherins function as regulators of synaptic plasticity by modulating spine morphology.␤-Catenin interacts with the cytoplasmic domain of classical cadherins and links cadherins and the actin cytoskeleton (19,20). ␤-Catenin and N-cadherin are present in axons and dendrites prior to synapse formation and then cluster at developing synapses and form a symmetrical adhesion structure in synaptic junctions (21). Moreover, it has been reported recently (10) that neural activity induces redistribution of ␤-catenin from dendritic shafts into spines, where it interacts with cadherin to influence synaptic...

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The mechanisms of testosterone-induced vasodilatation are not fully understood. This study investigated the effect of testosterone on nitric oxide (NO) synthesis and its molecular mechanism using human aortic endothelial cells (HAEC). Testosterone at physiological concentrations (1-100 nm) induced a rapid (15-30 min) increase in NO production, which was associated with phosphorylation and activation of endothelial NO synthase (eNOS). Then, the involvement of the androgen receptor (AR), which is abundantly expressed in HAEC, was examined. The effect of testosterone on eNOS activation and NO production were abolished by pretreatment with an AR antagonist nilutamide and by transfection with AR small interference RNA. In contrast, testosterone-induced eNOS phosphorylation was unchanged by pretreatment with an aromatase inhibitor or by transfection with ERalpha small interference RNA. 5alpha-Dihydrotestosterone, a nonaromatizable androgen, also stimulated eNOS phosphorylation. Next, the signaling cascade that leads to eNOS phosphorylation was explored. Testosterone stimulated rapid phosphorylation of Akt in a time- and dose-dependent manner, with maximal response at 15-60 min. The rapid phosphorylation of eNOS or NO production induced by testosterone was inhibited by Akt inhibitor SH-5 or by phosphatidylinositol (PI) 3-kinase inhibitor wortmannin. Co-immunoprecipitation assays revealed a testosterone-dependent interaction between AR and the p85alpha subunit of PI3-kinase. In conclusion, testosterone rapidly induces NO production via AR-dependent activation of eNOS in HAEC. Activation of PI3-kinase/Akt signaling and the direct interaction of AR with p85alpha are involved, at least in part, in eNOS phosphorylation.

Since radioiodination of human granulocyte colony-stimulating factor (G-CSF) is difficult, we synthesized a mutein of human G-CSF that retains full biological activity and receptor-binding capacity for at least 2 weeks after radioiodination. Receptors for human G-CSF were characterized in the plasma membrane fraction from the human term placenta (human placental membranes) and trophoblastic cells by using the III-labeled mutein of human G-CSF (KW-2228). The specific binding of III-labeled KW-2228 to placental membranes was pH-dependent, with maximal specific binding at pH 7.8; it increased linearly with protein to 3.7 mg of protein per ml and was both time-and temperature-dependent, with maximal binding at 4°C after a 24-hr incubation. When we examined the ability of hematopoietic growth factors to inhibit 2-5I-labeled KW-2228 binding, we found that KW-2228 and intact human G-CSF inhibited '25I-labeled KW-2228 binding, whereas erythropoietin or granulocyte-macrophage colonystimulating factor did not. Scatchard analysis revealed a single receptor type with a Bn,,., of 210 fmol/mg of protein and a Kd of 480 pM. The human G-CSF receptors on human placental membranes were shown to consist of two molecular species of 150 kDa and 120 kDa that could be specifically cross-linked to

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