Calpactin-depleted cytosolic proteins restore Ca(2+)-dependent secretion to digitonin-permeabilized bovine chromaffin...

Incubation of digitonin-permeabilized bovine chromaffin cells results in a loss of Ca(2+)-dependent catecholamine secretion. The addition of cytosolic proteins prevents this loss of secretory activity. It has been proposed that calpactin might be the protein which is responsible for preventing this loss of activity. The experiments described in this paper show that cytosolic proteins which have been depleted of calpactin are as effective as control cytosolic proteins in preventing the loss of Ca(2+)-dependent secretion. Thus, a cytosolic protein(s) other than calpactin appears to be responsible for preventing this loss of secretory activity.