Granzyme H induces cell death primarily via a Bcl-2-sensitive mitochondrial cell death pathway that does not require direct Bid activation

• Published in: Molecular immunology Vol. 54; no. 3-4; pp. 309 - 318
• Main Authors: Ewen, Catherine L., Kane, Kevin P., Bleackley, R. Chris
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.07.2013
• Subjects: Apoptosis; Apoptosis - drug effects; Apoptosis - physiology; Apoptosis Regulatory Proteins - metabolism; Bcl-2 proteins; BH3 Interacting Domain Death Agonist Protein - metabolism; Caspase 3 - metabolism; Caspases; Cell Death - drug effects; Cell Death - physiology; Cell Line, Tumor; Cell Membrane - drug effects; Cell Membrane - enzymology; Cell Membrane - metabolism; DFF45; DNA Damage; Enzyme Activation; Fas Ligand Protein - metabolism; fas Receptor - metabolism; Granzymes; Granzymes - metabolism; Granzymes - pharmacology; HeLa Cells; Humans; Jurkat Cells; K562 Cells; MCF-7 Cells; Membrane Potential, Mitochondrial - drug effects; Membrane Potential, Mitochondrial - physiology; Mitochondria - drug effects; Mitochondria - enzymology; Mitochondria - metabolism; Proto-Oncogene Proteins c-bcl-2 - metabolism; Recombinant Proteins - pharmacology; Bcl-2 proteins; DFF45; Caspases; Granzymes; Apoptosis
• ISSN: 0161-5890; 1872-9142
• DOI: 10.1016/j.molimm.2012.12.020

► The study brings clarity to the mechanism of Granzyme H-induced cell death. ► The mechanism is a Bcl-2 sensitive death pathway, but is not initiated by direct Bid cleavage. ► Granzyme H cleaves DFF45, leading to DNA damage. ► Granzyme H activates caspases in some cell lines, but they are not required for death. ► Granzyme H utilizes a different death mechanism than Granzyme B and Fas. Natural killer and T cell-mediated cytotoxicity is important for the elimination of viruses and transformed cells. The granule lytic pathway utilizes perforin and granzymes to induce cell death, while receptor-mediated lytic pathways rely on molecules such as FasL. Pro-apoptotic activities of Granzyme B (GrB) and Fas are well-established, and many of their cellular targets have been identified. However, humans express additional related granzymes – GrA, GrM, GrK, and GrH. Neither the cytotoxic potential of GrH, nor the mechanism by which GrH may induce target cell death is currently understood. We proposed that GrH would have pro-apoptotic activity that would be distinct from that of GrB and FasL, which could be relevant when Fas/FasL or GrB activity or death pathways were impaired. Our results, using a purified recombinant form of GrH, revealed that GrH induced cell death via a Bcl-2-sensitive mitochondrial pathway without direct processing of Bid. Additionally, neither the apoptosome nor caspase-3 was essential to the induction of GrH-mediated cell death. However, GrH did directly process DFF45, potentially leading to DNA damage. Our findings support the idea that multiple, non-redundant death pathways may be initiated by cytotoxic cells to counteract various immune evasion strategies.