Estimating the plasma membrane permeability of Taxus x media cells with the spin probe TEMPOL by EPR

Production of paclitaxel and other taxanes by cell suspension cultures of Taxus species is an alternative to their extraction from yew tree bark or shoots. Little is known about the mechanism of taxane transport in Taxus cells, in either cell cultures or plants. In our study we measured the influence of jasmonic acid (JA), an elicitor of taxane production, on plasma membrane permeability in cell suspensions of Taxus x media. TEMPOL spin probe was added to the suspension of cells grown in the presence of JA and to control cells. Reduction of TEMPOL in the cell interior was measured by electron paramagnetic resonance (EPR). Plasma membrane permeability was derived from the kinetics of reduction. JA was shown to decrease the membrane permeability of Taxus x media cells. The observed inhibition of the spin probe permeability by JA can be ascribed to modification of the membrane structure and lipid composition or, at least, to changes in the lipid lateral domain structures, thus affecting the transport of TEMPOL. The changed permeability to small uncharged molecules could influence the primary cellular metabolism and possibly also the transport of taxanes.