Cell cycle-dependent protein secretion by Saccharomyces cerevisiae

Synchronized Saccharomyces cerevisiae cell populations were used to examine secretion rates of a heterologous protein as a function of cell cycle posi tion. The synchronization procedure had a profound effect on the type and q uality of data obtained. When cell synchrony was induced by cell cycle-arre sting drugs, a significant physiological perturbation of cells was observed that obscured representative secretion data. In contrast, synchronization with centrifugal elutriation resulted in synchronized first-generation daug hter cells with undetectable perturbation of the physiological state. The s ynchronized cells did not secrete significant amounts of protein until they reached cell division, suggesting that the secretion process in these cell s is strongly cell cycle dependent. However, the maximum secretion rate of the synchronized culture (7-14 molecules/cell/second) was significantly low er than that of an asynchronous culture (29-51 molecules/cell/second). This result indicates that young daughter cells isolated in the synchronization process exhibit different protein secretion behavior than older mother cel ls that are absent in the synchronized cell population but present in the a synchronous culture. (C) 2001 John Wiley & Sons, Inc.