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Surface cathepsin B protects cytotoxic lymphocytes from self-destruction after degranulation.

Balaji KN, Schaschke N, Machleidt W, Catalfamo M, Henkart PA - J. Exp. Med. (2002)

Bottom Line: Flow cytometry shows that CTLs express low to undetectable levels of cathepsin B on their surface before degranulation, with a substantial rapid increase after T cell receptor triggering.Surface cathepsin B eluted from live CTL after degranulation by calcium chelation is the single chain processed form of active cathepsin B.Degranulated CTLs are surface biotinylated by the cathepsin B-specific affinity reagent NS-196, which exclusively labels immunoreactive cathepsin B.

View Article: PubMed Central - PubMed

Affiliation: Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Building 10, Bethesda, MD 20892, USA.

ABSTRACT
The granule exocytosis cytotoxicity pathway is the major molecular mechanism for cytotoxic T lymphocyte (CTL) and natural killer (NK) cytotoxicity, but the question of how these cytotoxic lymphocytes avoid self-destruction after secreting perforin has remained unresolved. We show that CTL and NK cells die within a few hours if they are triggered to degranulate in the presence of nontoxic thiol cathepsin protease inhibitors. The potent activity of the impermeant, highly cathepsin B-specific membrane inhibitors CA074 and NS-196 strongly implicates extracellular cathepsin B. CTL suicide in the presence of cathepsin inhibitors requires the granule exocytosis cytotoxicity pathway, as it is normal with CTLs from gld mice, but does not occur in CTLs from perforin knockout mice. Flow cytometry shows that CTLs express low to undetectable levels of cathepsin B on their surface before degranulation, with a substantial rapid increase after T cell receptor triggering. Surface cathepsin B eluted from live CTL after degranulation by calcium chelation is the single chain processed form of active cathepsin B. Degranulated CTLs are surface biotinylated by the cathepsin B-specific affinity reagent NS-196, which exclusively labels immunoreactive cathepsin B. These experiments support a model in which granule-derived surface cathepsin B provides self-protection for degranulating cytotoxic lymphocytes.

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Surface cathepsin B model for cytotoxic lymphocyte self-protection.
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fig8: Surface cathepsin B model for cytotoxic lymphocyte self-protection.

Mentions: The experiments described above provide strong support for the model of cytotoxic lymphocyte self-protection shown in Fig. 8 . The essential feature of this model is that self-protection is provided by surface membrane cathepsin B expressed as a result of degranulation. The data we have presented support this model with functional evidence that cathepsin B inhibitors sensitize cytotoxic lymphocytes to activation-induced suicide, as well as evidence for the cell surface expression of active cathepsin B triggered by degranulation. This model provides a rational explanation for the considerable literature bearing on cytotoxic lymphocyte self-protection (8). Because it postulates that expression of the critical cathepsin B self-protective molecule is local and transient, cytotoxic lymphocytes would be vulnerable to fratricidal attack. The model postulates that self-protection occurs before perforin-mediated membrane damage, which is the most upstream of the series of damaging events leading to target cell death.


Surface cathepsin B protects cytotoxic lymphocytes from self-destruction after degranulation.

Balaji KN, Schaschke N, Machleidt W, Catalfamo M, Henkart PA - J. Exp. Med. (2002)

Surface cathepsin B model for cytotoxic lymphocyte self-protection.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2196055&req=5

fig8: Surface cathepsin B model for cytotoxic lymphocyte self-protection.
Mentions: The experiments described above provide strong support for the model of cytotoxic lymphocyte self-protection shown in Fig. 8 . The essential feature of this model is that self-protection is provided by surface membrane cathepsin B expressed as a result of degranulation. The data we have presented support this model with functional evidence that cathepsin B inhibitors sensitize cytotoxic lymphocytes to activation-induced suicide, as well as evidence for the cell surface expression of active cathepsin B triggered by degranulation. This model provides a rational explanation for the considerable literature bearing on cytotoxic lymphocyte self-protection (8). Because it postulates that expression of the critical cathepsin B self-protective molecule is local and transient, cytotoxic lymphocytes would be vulnerable to fratricidal attack. The model postulates that self-protection occurs before perforin-mediated membrane damage, which is the most upstream of the series of damaging events leading to target cell death.

Bottom Line: Flow cytometry shows that CTLs express low to undetectable levels of cathepsin B on their surface before degranulation, with a substantial rapid increase after T cell receptor triggering.Surface cathepsin B eluted from live CTL after degranulation by calcium chelation is the single chain processed form of active cathepsin B.Degranulated CTLs are surface biotinylated by the cathepsin B-specific affinity reagent NS-196, which exclusively labels immunoreactive cathepsin B.

View Article: PubMed Central - PubMed

Affiliation: Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Building 10, Bethesda, MD 20892, USA.

ABSTRACT
The granule exocytosis cytotoxicity pathway is the major molecular mechanism for cytotoxic T lymphocyte (CTL) and natural killer (NK) cytotoxicity, but the question of how these cytotoxic lymphocytes avoid self-destruction after secreting perforin has remained unresolved. We show that CTL and NK cells die within a few hours if they are triggered to degranulate in the presence of nontoxic thiol cathepsin protease inhibitors. The potent activity of the impermeant, highly cathepsin B-specific membrane inhibitors CA074 and NS-196 strongly implicates extracellular cathepsin B. CTL suicide in the presence of cathepsin inhibitors requires the granule exocytosis cytotoxicity pathway, as it is normal with CTLs from gld mice, but does not occur in CTLs from perforin knockout mice. Flow cytometry shows that CTLs express low to undetectable levels of cathepsin B on their surface before degranulation, with a substantial rapid increase after T cell receptor triggering. Surface cathepsin B eluted from live CTL after degranulation by calcium chelation is the single chain processed form of active cathepsin B. Degranulated CTLs are surface biotinylated by the cathepsin B-specific affinity reagent NS-196, which exclusively labels immunoreactive cathepsin B. These experiments support a model in which granule-derived surface cathepsin B provides self-protection for degranulating cytotoxic lymphocytes.

Show MeSH
Related in: MedlinePlus