Chemical hormesis in cell growth: A molecular target at the cell surface

A multifunctional ubiquinol (NADH) oxidase with protein disulfide-thiol int erchange activity of the cell surface, abbreviated as NOX, is described as a molecular target for chemical hormesis of cell growth. The activity of th e NOX correlates with rate of cell enlargement, which helps to determine ho w rapidly cells will divide. When NOX activity is inhibited, cells fail to enlarge following division and the result is a population of small cells un able to reach the minimum size required for them to divide again. In plants , cells fail to enlarge when NOX activity is inhibited, When NOX activity i s stimulated or constitutively activated, as in cancer, cells enlarge more rapidly and the rate of cell division also is enhanced. Both cell growth an d NOX activity are sometimes stimulated by low concentrations of normally i nhibitory molecules. These properties define chemical hormesis, making the NOX molecule a molecular target to explain hermetic growth responses and to utilize hermetic principles to increase, for example, crop yields with pla nts. The NOX activity at the cell surface oscillates with a temperature-com pensated 24-min ultradian (<24 h) periodicity. The indicated function of th e NOX protein as a time-keeping mechanism adds to its potential importance as a molecular target for chemical hormesis. Copyright (C) 2000 John Wiley & Sons, Ltd.