Human T-lymphocyte serine proteases (granzymes) 1, 2, and 3 mediated DNA fragmentation in susceptible target cells

Role of TNF family ligands in antitumor activity of natural killer cells

NK cells have the ability to destroy tumor cells by two main cytotoxic pathways, the well-known perforin/granzyme-mediated secretory/necrotic killing and the newly defined TNF family ligand-mediated apoptotic killing. The former mechanism is operative mainly against a few cultured leukemia cell targets, while the latter mediates substantial activity against most tumor cell targets. It also appears from emerging data that the apoptotic mechanism is the main antitumor pathway in vito. This review is focused on the apoptotic mechanism of killing, the molecules and cell signaling pathways involved in this process, and its potential biologic significance along with its relation to the secretory/necrotic cytolytic pathway.

Contradictory Concepts in the Etiology and Regression of Kaposi's Sarcoma. The Ferenc Györkey Memorial Lecture

The Introduction is an overview of 3 decades of works performed by Professor Ferenc Györkey (in many cases in collaboration with the author) and aimed at the elucidation of viral participation in the etiology of arteriosclerosis, SLE, hairy cell leukemia, HD, AIDS and KS. Controversial issues surrounding the etiology, treatment and regression of KS are discussed in terms of paracrine and autocrine loops of growth factors; protooncogene-oncogene activations, immunosuppression and retro- and/or herpesviral etiology. In regressing KS lesions the roles played by Fas, Bcl-2, Bax, TNFß; apoptotic-antiapoptotic events; and antiangiogenesis agents especially that of Hu-r-IFNa are elaborated on.

Granzymes (lymphocyte serine proteases): characterization with natural and synthetic substrates and inhibitors

Natural killer (NK) and cytotoxic T-lymphocytes (CTLs) kill cells within an organism to defend it against viral infections and the growth of tumors. One mechanism of killing involves exocytosis of lymphocyte granules which causes pores to form in the membranes of the attacked cells, fragments nuclear DNA and leads to cell death. The cytotoxic granules contain perforin, a pore-forming protein, and a family of at least 11 serine proteases termed granzymes. Both perforin and granzymes are involved in the lytic activity. Although the biological functions of most granzymes remain to be resolved, granzyme B clearly promotes DNA fragmentation and is directly involved in cell death. Potential natural substrates for Gr B include procaspases and other proteins involved in cell death. Activated caspases are involved in apoptosis. The search continues for natural substrates for the other granzymes. The first granzyme crystal structure remains to be resolved, but in the interim, molecular models of granzymes have provided valuable structural information about their substrate binding sites. The information has been useful to predict the amino acid sequences that immediately flank each side of the scissile peptide bond of peptide and protein substrates. Synthetic substrates, such as peptide thioesters, nitroanilides and aminomethylcoumarins, have also been used to study the substrate specificity of granzymes. The different granzymes have one of four primary substrate specificities: tryptase (cleaving after Arg or Lys), Asp-ase (cleaving after Asp), Met-ase (cleaving after Met or Leu), and chymase (cleaving after Phe, Tyr, or Trp). Natural serpins and synthetic inhibitors (including isocoumarins, peptide chloromethyl ketones, and peptide phosphonates) inhibit granzymes. Studies of substrate and inhibitor kinetics are providing valuable information to identify the most likely natural granzyme substrates and provide tools for the study of key reactions in the cytolytic mechanism.