APOPTOSIS BY A CYTOSOLIC EXTRACT FROM FAS-ACTIVATED CELLS

Fas is a type I membrane protein and its activation by binding of the Fas ligand or an agonistic anti-Fas antibody induces apoptosis in Fas- bearing cells, In this report we prepared lysates from cells treated w ith anti-Fas antibody. The lysates induced apoptotic morphological cha nges in nuclei from normal mouse liver, accompanied by DNA degradation . The apoptosis-inducing activity was quickly generated in cells by an ti-Fas antibody and was found in the soluble cytosolic fraction, Induc tion of the activity in cells was inhibited by a tetrapeptide, acetyl- Tyr-Val-Ala-Asp-chloromethylketone, a specific inhibitor of interleuki n-1 beta converting enzyme. Addition of COS cell lysates containing Bc l-2 to the assay significantly inhibited the apoptotic process, indica ting that the in vitro process reflected apoptosis that occurs in inta ct cells.