Isolation and biochemical and functional characterization of perforin 1 from cytolytic T-cell granules.

Abstract

The Ca2+-dependent cytolytic activity of isolated T-lymphocyte granules was purified to apparent homogeneity by high-salt extraction, gel filtration, and ion-exchange chromatography. The lytic activity resided in a 72- to 75-kDa protein of cytolytic granules. Incubation of the isolated protein with erythrocytes in the presence of Ca2+ ions resulted in hemolysis and the formation of membrane lesions of 160 .ANG. in diameter, corresponding in size and morphology to membrane lesions formed on target cells by cloned, intact natural killer (NK) and cytolytic T lymphocytes. Hence, the 75-kDa granule protein is identified as monomeric perforin 1 (P1), postulated previously from the analysis of membrane lesions formed during NK and T-cell-mediated cytolysis. P1-mediated hemolysis is Ca2+-dependent and is inhibited by Zn2+ ions. Lysis is accompanied by the polymerization of P1 to membrane-associated tubular complexes (poly-P1) that form large transmembrane pores. P1 causes a rapid membrane depolarization of J774 cells in the presence of Ca2+. Purified P1 also induces transmembrane monovalent and divalent ion flow across lipid vesicles only in the presence of Ca2+. Whole-cell patch-clamp recordings of S49 lymphoma cells show a P1-dependent inward membrane current flow in the presence but not in the absence of Ca2+. The current increase can be dissected as a summation of discrete current events, indicative of formation of functional channels by polymerization of P1.