Discordant Regulation of Granzyme H and Granzyme B Expression in Human Lymphocytes

Abstract

We analyzed the expression of granzyme H in human blood leukocytes, using a novel monoclonal antibody raised against recombinant granzyme H. 33-kDa granzyme H was easily detected in unfractionated peripheral blood mononuclear cells, due to its high constitutive expression in CD3 ؊ CD56 ؉ natural killer (NK) cells, whereas granzyme B was less abundant. The NK lymphoma cell lines, YT and Lopez, also expressed high granzyme H levels. Unstimulated CD4؉ and particularly CD8 ؉ T cells expressed far lower levels of granzyme H than NK cells, and various agents that classically induce T cell activation, proliferation, and enhanced granzyme B expression failed to induce granzyme H expression in T cells. Also, granzyme H was not detected in NK T cells, monocytes, or neutrophils. There was a good correlation between mRNA and protein expression in cells that synthesize both granzymes B and H, suggesting that gzmH gene transcription is regulated similarly to gzmB. Overall, our data indicate that although the gzmB and gzmH genes are tightly linked, expression of the proteins is quite discordant in T and NK cells. The finding that granzyme H is frequently more abundant than granzyme B in NK cells is consistent with a role for granzyme H in complementing the pro-apoptotic function of granzyme B in human NK cells.

Granzyme H of Cytotoxic Lymphocytes Is Required for Clearance of the Hepatitis B Virus through Cleavage of the Hepatitis B Virus X Protein

“…GzmH is predominantly expressed in human NK cells regardless of the activation status (15). It suggests that GzmH may exert critical roles in innate immunity induced by NK cells.…”

“…GzmH is mainly expressed at a high level in NK cells (15), which suggests that GzmH may play an important role in innate immunity against pathogens or transformed tumors. We and Fellows et al previously demonstrated that GzmH can induce apoptosis of target tumor cells using different death pathways (5,6).…”

“…Cancer Centre, East Melbourne, VIC, Australia (15)], rabbit polyclonal Ab against NM23-H1 (Santa Cruz Biotechnology), GzmH (Abcam), Alexa 488-conjugated donkey anti-mouse IgG (Molecular Probes), Alexa 594-conjugated donkey anti-rabbit IgG (Molecular Probes), PE-conjugated goat anti-mouse IgG (eBioscience), and PE-conjugated goat anti-rabbit IgG (eBioscience). Concanamycin A (CMA), streptolysin O (SLO), and Hoechst 33342 were from Sigma-Aldrich.…”

Cleavage of La protein by granzyme H induces cytoplasmic translocation and interferes with La-mediated HCV-IRES translational activity

“…7 Although gzmB and cathepsin G are highly conserved between human and mice, the precise functional ortholog of human gzmH has not been determined. 8 Interestingly, gzmH is constitutively expressed in NK cells irrespective of the activation status, and in contrast to GzmB, it is not present in activated CD8 þ T cells, 9,10 suggesting that gzmH might play a critical role in the cytotoxic arm of the innate immune response. GzmH has chymotrypsin-like (chymase) activity and is capable of cleaving synthetic substrates with a clear preference of Phe and Tyr in the P 1 site.…”

Conservation of the Extended Substrate Specificity Profiles Among Homologous Granzymes Across Species

“…Furthermore, both granzymes are expressed by NK and CD4ϩ T-cells (1,2): GrH is constitutively expressed at high levels in NK cells and less in CD4ϩ T cells, whereas GrC expression can be observed after stimulation. Thus, their overlapping expression profiles further support possible functional similarities between mouse GrC and human GrH.…”