Dorothy M. Morré

Auxin-Modulated Protein Disulfide-Thiol-Interchange Activity from Soybean Plasma Membranes

The renaturation of scrambled (oxidized and inactive) RNase A is catalyzed by soybean (Glycine max cv Williams 82) plasma membranes. The catalysis is stimulated by the auxin herbicide 2,4-dichlorophenoxyacetic acid or by the natural auxin indole-3-acetic acid. The inactive auxin analog, 2,3-dichlorophenoxyacetic acid, is without effect. The activity occurs in the absence of external electron acceptors or donors and therefore appears to be a true disulfide-thiol-interchange activity between protein disulfides and thiols of RNase A and those of plasma membrane proteins. The activity is not affected by a mixture of reduced and oxidized glutathione. However, no auxin-stimulated activity was observed in the presence of either oxidized glutathione or reduced glutathione alone, a response characteristic of the previously described auxin-stimulated NADH oxidase activity of soybean plasma membranes. Taken together, the results suggest the operation in the plant plasma membrane of a protein disulfide-thiol-interchange activity that is stimulated by auxins. The auxin stimulations of the interchange activity are prevented by glutathione, reduced glutathione, and brefeldin A at concentrations that also prevent auxin stimulation of NADH oxidation by isolated plasma membranes and inhibit, as well, the auxin-stimulated elongation of excised segments of soybean hypocotyls.

Early Detection: An Opportunity for Cancer Prevention Through Early Intervention

Cancer is the second leading disease cause of death in the United States. A group of more than 100 different and distinctive diseases, cancer may involve any tissue of the body. Estimates are that there were over 1.5 million cases in 2010 in the United States alone. Only a small fraction (less than 20%) of cancers are diagnosed at a localized stage where curative therapy is effective. Most cancers are diagnosed only after the primary tumor has already metastasized so that chemotherapy is required for treatment. Hence, early detection is a favored opportunity to reduce cancer mortality. By detecting cancer in its very earliest stages when perhaps only a small number of cells are present, it is possible that early intervention will be effective in preventing further development of the incipient cancer thereby resulting in what might be viewed as curative prevention.