Disease relevance of SERPINB9

• SERPINB9 is the only known human intracellular inhibitor of granzyme B (GrB), the effector molecule in immunity against cytomegalovirus (CMV) and in renal allograft rejection [1].
• We tested this hypothesis by quantifying numbers of tumor cells positive for active caspase 3, Bcl-2, and PI9, respectively, in pretreatment biopsies of systemic anaplastic large cell lymphoma (ALCL) patients and by comparing these numbers with clinical outcome [2].
• Purified recombinant PI9 failed to inhibit the amidolytic activities of trypsin, papain, thrombin, or Staphylococcus aureus endoproteinase Glu-C and did not form an SDS-stable complex when incubated with thrombin [3].
• In addition, the reactive center loop of PI9 exhibits 54% identity with residues found in the reactive center loop of the cowpox virus CrmA serpin [3].
• To investigated if PI-9 is important in the response to ASI, paraffin-embedded tissues from stage III or IV melanoma patients were stained [4].

High impact information on SERPINB9

• We report here that the serine proteinase inhibitor (serpin) PI-9 accounts for the endogenous caspase-1 inhibitory activity in human SMCs and prevents processing of the enzyme's natural substrates, IL-1beta and IL-18 precursor [5].
• In this study, the impact of PI-9 and bcl-2 expression on the sensitivity of lymphomas to T- and natural killer (NK) cell-mediated cytotoxicity was analyzed [6].
• All lymphoma cells were sensitive to cytolysis by specific T cells and cytokine-activated NK cells, and no difference in sensitivity was observed with respect to PI-9 or bcl-2 expression [6].
• We found PI-9 expression in 10 of 18 lymphoma cell lines and in 9 of 14 primary lymphomas [6].
• Actual execution of apoptosis depends on proper functioning of effector caspases, particularly caspase 3, and on the expression levels of apoptosis-regulating proteins, including Bcl-2 and the recently identified granzyme B- specific protease inhibitor 9 (PI9) [2].

Chemical compound and disease context of SERPINB9

• In HIV-1 infected cells, the inhibitory activity of HIV-1 caused by B9-C23 and C1-C26, the A1-C26 homologues corresponding to the C-terminal sections of serpin B9 and serpin C1, was much lower than that obtained with A1-C26 [7].
• Fourteen patients with advanced head and neck carcinomas received a monthly intravenous regimen of Adriamycin, 40 mg/m2, day 1; cyclophosphamide, 400 mg/m2, day 3; and cis-diamminedichloroplatinum, 20 mg/m2/1 hour, days 1-3 (CAP-3) [8].

Biological context of SERPINB9

• A serpin gene cluster on human chromosome 6p25 contains PI6, PI9 and ELANH2 which have a common structure almost identical to the 18q21 ovalbumin serpin genes [9].
• In vitro nuclear transport assays show that PI-9 accumulates at a rate above that of passive diffusion, that it requires cytosolic factors but not ATP, and that it does not bind an intranuclear component [10].
• Amino-terminal sequence analyses provided evidence that inhibition of elastase occurred through the use of Cys(342) as the reactive P(1) amino acid residue in the PI9 reactive site loop [11].
• We isolated genomic clones containing the PI-9 promoter region, identified a putative transcription start site, and carried out transient transfections of PI-9-luciferase reporter gene constructs [12].
• Inhibition of transcription with actinomycin D resulted in identical rates of PI-9 mRNA decay in the presence and absence of estrogen [12].

Anatomical context of SERPINB9

• PI-9 should therefore be found in cytotoxic lymphocyte and bystander cell nuclei to ensure complete protection against graB [10].
• Here we demonstrate by microscopy and subcellular fractionation experiments that PI-9 is present in the nuclei of human cytotoxic cells, endothelial cells, and epithelial cells [10].
• Proteinase inhibitor 9 (PI-9) is a human serpin present in the cytoplasm of cytotoxic lymphocytes and epithelial cells [10].
• Because dendritic cells (DCs) acquire characteristics similar to those of target cells to activate naive CD8(+) T cells and therefore may also require protection against grB, we investigated the expression of PI-9 in DCs [13].
• PI-9 is up-regulated in response to grB production and degranulation, and associates with grB-containing granules in activated CTLs and NK cells [13].

Associations of SERPINB9 with chemical compounds

• Furthermore, PI-9 is exported from nuclei via a leptomycin B-sensitive pathway, implying involvement of the export factor Crm1p [10].
• Inhibition occurred with an overall K(i)' of 221 pM and a second-order association rate constant of 1.5 x 10(5) M(-1) s(-1), indicating that PI9 is a potent inhibitor of this serine proteinase in vitro [11].
• Western blot analysis showed that estrogen strongly increases PI-9 protein levels [12].
• Mutational inactivation of three potential imperfect estrogen response elements in the PI-9 5'-flanking region had no effect on moxestrol estrogen receptor induction [12].
• Estrogens induced PI-9 mRNA within 2 h, PI-9 mRNA levels reached a plateau of 30-40-fold induction in 4 h, and induction was not blocked by cycloheximide, indicating that induction of PI-9 mRNA is a primary response [12].

Regulatory relationships of SERPINB9

• These results suggest that PI-9 serves to inactivate misdirected granzyme B following cytotoxic cell degranulation [14].
• Furthermore, PI-9 is expressed in monocyte-derived DCs and is up-regulated upon TNF-alpha-induced maturation of monocyte-derived DCs [13].

Other interactions of SERPINB9

• PI6 and PI9 are almost identical in structure to the ovalbumin serpin genes at 18q21 [9].
• The two novel serpins encoded by the two novel cDNA sequences have been designated as proteinase inhibitor 8 (PI8) and proteinase inhibitor 9 (PI9) [3].
• We conclude that the nucleocytoplasmic distribution of PI-9 and related serpins involves a nonconventional nuclear import pathway and Crm1p [10].
• In this report, we describe the inhibition of human neutrophil elastase by recombinant human PI9 [11].
• The role of CAP3 in CD95 signaling: new insights into the mechanism of procaspase-8 activation [15].

Analytical, diagnostic and therapeutic context of SERPINB9

• Therefore, using specific enzyme-linked immunosorbent assays, we addressed the presence of circulating SERPINB9 during primary CMV infection, subclinical rejection, acute rejection, and uncomplicated posttransplantation course [1].
• PI9 was purified to homogeneity from the yeast cell lysate by a combination of heparin-agarose chromatography and Mono Q fast protein liquid chromatography and migrated as a single band in SDS-polyacrylamide gel electrophoresis with an apparent molecular mass of 42 kDa [3].
• RESULTS: PI-9 is expressed in melanoma cells and expression in metastasized melanoma cells is, in this group of patients, an adverse prognostic marker with regard to overall and disease-free survival [4].
• Although it cannot be proven that PI-9 expression is directly responsible for failure of immunotherapy, these data suggest that expression of PI-9 could be an important immune escape mechanism and that modulation of this inhibitor may enhance the efficacy of immunotherapy [4].
• The granzyme B inhibitor SERPINB9 (protease inhibitor 9) circulates in blood and increases on primary cytomegalovirus infection after renal transplantation [1].

References