THE S-100 PROTEIN CAUSES AN INCREASE OF INTRACELLULAR CALCIUM AND DEATH OF PC12 CELLS

The S-100 protein-PC12 cell interaction has been studied as a model system of the possible physiological role played by S-100 protein in the nervous system. The data reported demonstrate that S-100 exerts a cytotoxic action which eventually leads to PC12 cell death, regardless of the cell cycle phase. The effect is specific for the S-100 isoforms, which are made up of two identical subunits and is abolished by a monoclonal antibody directed against the same isoforms. Other isoforms and/or calcium-binding proteins, such as troponin or calmodulin, do not induce the same effects. The action of S-100 on cell viability is not detectable in other cell lines of different embryological origin, such as 3T3, L1210, GH3. S-100 causes a rapid and considerable increase (two- to three-fold) of intracellular Ca2+ concentration in PC12 cells accompanied by cytostatic and cytotoxic action. It is postulated that this action also occurs in vivo, as part of the physiological action of this protein.