The small guanosine triphosphatases (GTPases) Cdc42 and Rac1 regulate E-cadherin-mediated cell-cell adhesion. IQGAP1, a target of Cdc42 and Rac1, was localized with E-cadherin and beta-catenin at sites of cell-cell contact in mouse L fibroblasts expressing E-cadherin (EL cells), and interacted with E-cadherin and beta-catenin both in vivo and in vitro. IQGAP1 induced the dissociation of alpha-catenin from a cadherin-catenin complex in vitro and in vivo. Overexpression of IQGAP1 in EL cells, but not in L cells expressing an E-cadherin-alpha-catenin chimeric protein, resulted in a decrease in E-cadherin-mediated cell-cell adhesive activity. Thus, IQGAP1, acting downstream of Cdc42 and Rac1, appears to regulate cell-cell adhesion through the cadherin-catenin pathway.

We have previously shown that IQGAP1, a recently identified target for Cdc42 and Rac1 small GTPases, showed a distribution similar to that of cortical actin cytoskeleton at the membrane ruffling area induced by insulin and Rac1 val12 (Kuroda, S., Fukata, M., Kobayashi, K., Nakafuku, M., Nomura, N., Iwamatsu, A., and Kaibuchi, K.

A 17␤-estradiol (E2)-degrading bacterium was isolated from activated sludge in a sewage treatment plant in Tokyo, Japan. The isolate was suggested to be a new Novosphingobium species. Gas chromatography-mass spectrometry and 1 H nuclear magnetic resonance analyses of the metabolites of E2 degradation suggested that no toxic products accumulated in the culture medium.There has been increasing concern recently over the potential of sewage treatment plant (STP) effluent to cause estrogenic effects on aquatic fauna. Widespread sexual disruption, or so-called feminization, is thought to be due to environmental contaminants in the effluent and has been observed for riverine fish in several developed nations, including the United Kingdom, the United States, and Japan (3,4,7,8,10,13). While there still remains some room for discussion about the chemicals that cause this phenomenon, natural estrogens entering the environment through the excretions of humans, domestic or farm animals, and wildlife are thought to be the most likely suspects, because they induce biological effects at environmentally relevant concentrations, on the order of nanograms per liter (12,18,21). Among the natural estrogens, 17␤-estradiol (E2) is the most potent and is found ubiquitously in many water systems (2,9,11,14,24,28). Therefore, it is thought that E2 is responsible for the majority of the estrogenic effects found for STP effluent.Although the fate and behavior of E2 after excretion, during processing in STPs, or following discharge into rivers are not fully understood, there is some evidence supporting the importance of this problem. The efficiency of removal of natural estrogens, including E2, during STP processing is estimated to be 50 to 90%, depending on the facility and the location (2, 14). However, this removal is thought to be mainly due to adsorption of E2 into activated sludge or other factors independent of microbial degradation, because it has been suggested previously that natural steroidal estrogens, including E2, are poorly degraded during STP processing (17,19). Furthermore, the proportion of steroidal estrogens remaining in the effluent is still capable of producing estrogenic effects (18). It has also been reported previously that conjugated E2 (an estrogenically inactive form) excreted from humans and animals is converted back into free E2 (the active form) before or during passage through the STP, suggesting that microbes in the process can cleave the conjugates (16). These facts, considered together with the increasing public consciousness regarding environmental preservation and the views of scientists (19, 26), make it clear that the degradation capabilities and removal efficiencies of STPs need to be improved further. Moreover, recent overpopulation in urban areas may make the feminization problem more serious. These prospects led us to search for microorganisms with strong E2-degrading activity.To find microbes with E2-degrading activity, we collected 11 samples, including 4 soil and 3 water samples from natural en...

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