• IMMUNE NETWORK
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• v.22 no.3
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• pp.28.1-28.11
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• 2022

The 26S proteasome irreversibly hydrolyzes polyubiquitylated substrates to maintain protein homeostasis; it also regulates immune responses by generating antigenic peptides. An alternative form of the 26S proteasome is the immunoproteasome, which contains substituted catalytic subunits (β1i/PSMB9, β2i/PSMB10, and β5i/PSMB8) instead of constitutively expressed counterparts (β1/PSMB6, β2/PSMB7, and β5/PSMB5). The immunoproteasome expands the peptide repertoire presented on MHC class I molecules. However, how its activity changes in this context is largely elusive, possibly due to the lack of a standardized methodology to evaluate its specific activity. Here, we describe an assay protocol that measures the immunoproteasome activity of whole-cell lysates using commercially available fluorogenic peptide substrates. Our results showed that the most accurate assessment of immunoproteasome activity could be achieved by combining β5i-targeting substrate Ac-ANW-AMC and immunoproteasome inhibitor ONX-0914. This simple and reliable protocol may contribute to future studies of immunoproteasomes and their pathophysiological roles during viral infection, inflammation, and tumorigenesis.

• IMMUNE NETWORK
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• v.9 no.6
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• pp.285-288
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• 2009

The expression pattern of immunoproteasomes in human thymus has not been analyzed but may have important consequences during thymic selection. Here we examined the expression patterns of immunoproteasome subunits in fetal and adult thymic tissues by immunohistochemistry and found that all three subunits are expressed in both cortical and medullary stromal cells. These data suggest that thymic selection in human can be affected by peptide repertoires generated by immunoproteasomes.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.11
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• pp.6399-6402
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• 2013

Hematological malignancies (HM) are a group of neoplasms derived from the cells of the bone marrow and lymphatic system. Genetic factors leading to susceptibility to HM have been investigated for years but little is known yet. Low molecular weight polypeptide (LMP) 2 and LMP7 genes are important subunits of the immunoproteasome and play significant role in antigen presentation. The polymorphisms of LMP genes have been reported to be risk factors for various types of diseases. The aim of this study was to investigate the association of LMP2 and LMP7 polymorphisms with the occurrence of particular types of HM. A total of 132 patients with HM and 130 control subjects were investigated. No significant difference was obtained in the distribution of genotype and allele frequencies of LMP7 gene in HM patients and the control group. On the other hand, the prevalence of LMP2-AA genotype was found to be higher in acute myeolid leukemia (AML) patients while it was significantly lower in multiple myeloma (MM) cases than in the control subjects. Our results suggested that LMP7 could not be a risk factor for susceptibility to HM, whereas LMP2 polymorphisms could play a role in the development of AML and MM.