Granulysin Delivered by Cytotoxic Cells Damages Endoplasmic Reticulum and Activates Caspase-7 in Target Cells

Abstract

Granulysin is a human cytolytic molecule present in cytotoxic granules with perforin and granzymes. Recombinant 9-kDa granulysin kills a variety of microbes, including bacteria, yeast, fungi, and parasites, and induces apoptosis in tumor cells by causing intracellular calcium overload, mitochondrial damage, and activation of downstream caspases. Reasoning that granulysin delivered by cytotoxic cells may work in concert with other molecules, we crossed granulysin transgenic (GNLY+/−) mice onto perforin (perf)- or granzyme B (gzmb)-deficient mice to examine granulysin-mediated killing in a more physiologic whole-cell system. Splenocytes from these animals were activated in vitro with IL-15 to generate cytolytic T cells and NK cells. Cytotoxic cells expressing granulysin require perforin, but not granzyme B, to cause apoptosis of targets. Whereas granzyme B induces mitochondrial damage and activates caspases-3 and -9 in targets, cytotoxic cell-delivered granulysin induces endoplasmic reticulum stress and activates caspase-7 with no effect on mitochondria or caspases-3 and -9. In addition, recombinant granulysin and cell-delivered granulysin activate distinct apoptotic pathways in target cells. These findings suggest that cytotoxic cells have evolved multiple nonredundant cell death pathways, enabling host defense to counteract escape mechanisms employed by pathogens or tumor cells.

The Perforin Pore Facilitates the Delivery of Cationic Cargos

“…These are not mutually exclusive possibilities. Interestingly there is indirect evidence that granulysin, a component of the CL granule, is delivered by perforin into target cells (54). This is consistent with data presented here as granulysin is known to be cationic (55).…”

Granule Exocytosis of Granulysin and Granzyme B as a Potential Key Mechanism in Vaccine-Induced Immunity in Cattle against the Nematode Ostertagia ostertagi

“…Granulysin is known for its direct lytic effect on a wide variety of pathogens (36,37), its role in apoptosis (38,39), and its alarmin-like function (40). Granzyme B, a serine protease, is associated with granulysin in some of these functions, particularly in the induction of apoptosis.…”

Granulysin expression and the interplay of granulysin and perforin at the maternal–fetal interface

“…It is released from effector cells by exocytosis in preformed granules, in proximity to target cells (Saini et al, 2011). NK cells spontaneously release GNLY within 2 h, while T cells need three to five days for GNLY release after their activation .…”