Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.25.1 (proteasome)
28,817 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Proteasomal proteolysis relies on the activity of six catalytically active proteasomal subunits (beta1, beta2, beta5, beta1i, beta2i and beta5i). Applying a functional proteomics approach, we used a recently developed activity-based, cell-permeable proteasome-specific probe that for the first time allows differential visualization of individual active proteasomal subunits in intact primary cells. In primary leukemia samples, we observed remarkable variability in the amounts of active beta1/1i-, beta2/2i- and beta5/5i-type of subunits, contrasting with their constant protein expression. Bortezomib inhibited beta5- and beta1-type, but to a lesser extend beta2-type of subunits in live primary cells in vitro and in vivo. When we adapted the bortezomib-sensitive human acute myeloid leukemia cell line HL-60 to bortezomib 40 nM (HL-60a), proteasomal activity profiling revealed an upregulation of active subunits, and residual beta1/beta5-type of activity could be visualized in the presence of bortezomib 20 nM, in contrast to control cells. In a panel of cell lines from hematologic malignancies, the ratio between beta2-type and (beta1 + beta5)-type of active proteasomal polypeptides mirrored different degrees of bortezomib sensitivity. We thus conclude that the proteasomal activity profile varies in primary leukemia cells, and that the pattern of proteasomal subunit activity influences the sensitivity of hematologic malignancies toward bortezomib.
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PMID:Activity patterns of proteasome subunits reflect bortezomib sensitivity of hematologic malignancies and are variable in primary human leukemia cells. 1702 15

Microbial infections induce the replacement of constitutive proteasomes by immunoproteasomes (I-proteasomes). I-proteasomes support efficient generation of MHC class I epitopes and influence immunodominance hierarchies of CD8(+) T cells. Recently, the function of I-proteasomes in antimicrobial responses was challenged by showing that the lack of I-proteasomes has no effect on induction and function of lymphocytic choriomeningitis virus-specific CD8(+) T cells. Here, we show that infection with Listeria monocytogenes rapidly induces I-proteasomes in nonlymphoid tissues, which leads to enhanced generation of protection relevant CD8(+) T cell epitopes. I-proteasome-deficient mice (beta5i(-/-) mice) exhibited normal frequencies of L. monocytogenes-specific CD8(+) T cells. However, clearance of L. monocytogenes in liver but not spleen was significantly impaired in I-proteasome-deficient mice. In summary, our studies demonstrate that induction of I-proteasomes is required for CD8(+) T cell-mediated elimination of L. monocytogenes from nonlymphoid but not lymphoid tissues.
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PMID:Immunoproteasomes are essential for clearance of Listeria monocytogenes in nonlymphoid tissues but not for induction of bacteria-specific CD8+ T cells. 1705 53

The 20 S proteasomes are cylinder-shaped heteromeric dimers with a subunit configuration of alpha7, beta7, beta7, alpha7. Replacement of the three active site-containing standard beta-subunits (beta1, beta2, beta5) by immuno-beta-subunits (beta1i, beta2i, beta5i) results in formation of 20 S immuno-proteasomes, while only partial replacement leads to intermediate-type proteasomes. Synthesis of immuno-subunits can be induced by interferon-gamma, which causes a complete transformation of three subtypes of standard proteasomes into three subtypes of intermediate-type proteasomes in HeLa cells, a process that results in a change in the proteolytic activities of the enzymes. HeLa cells producing the proteasome beta1-subunit tagged with the Fc region-binding ZZ domain of protein A were grown in the presence of interferon-gamma. From these cells, we have purified 20 S proteasomes by using IgG-affinity resin and analysed them by 2D PAGE. Our study showed that subunit replacement can be confined to one half of the proteasome cylinder, resulting in the formation of intermediate-type proteasomes with "asymmetric" subunit composition. Analysis of proteasomes purified from the cytoplasm, nucleoplasm, and microsomes of HeLa S3 cells reveals that all three compartments are furnished with intermediate-type proteasomes of different subtype and subunit composition, exhibiting different specific proteolytic activities.
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PMID:Intermediate-type 20 S proteasomes in HeLa cells: "asymmetric" subunit composition, diversity and adaptation. 1780 16

Following cellular stress or tissue injury, the proteasome plays a critical role in protein degradation and signal transduction. The present study examined the beta-subunit expression of constitutive proteasomes (beta1, beta2, and beta5), immunoproteasomes (beta1i, beta2i, and beta5i) and the 11S proteasome activator, PA28alpha, in the rat CNS after traumatic brain injury (TBI). Concomitant measures assessed changes in proteasome activities. Quantitative real time PCR results indicated that beta1 and beta2 mRNA levels were not changed, while beta5 mRNA levels were significantly decreased in injured CNS following TBI. However, beta1i, beta2i, beta5i, and PA28alpha mRNA levels were significantly increased in the injured CNS. Western blotting studies found that beta1, beta2, beta5, beta2i, and beta5i subunit protein levels remained unchanged in the injured CNS, but beta1i and PA28alpha protein levels were significantly elevated in ipsilateral cerebral cortex and hippocampus. Proteasome activity assays found that peptidyl glutamyl peptide hydrolase-like and chymotrypsin-like activity were significantly reduced in the CNS after TBI, and that trypsin-like proteasome activity was increased in the injured cerebral cortex. Our results demonstrated that both proteasome composition and function in the CNS were affected by trauma. Treatments that preserve proteasome function following CNS injury may be beneficial as an approach to cerebral neuroprotection.
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PMID:Alterations of cerebral cortex and hippocampal proteasome subunit expression and function in a traumatic brain injury rat model. 1794 70

In amyotrophic lateral sclerosis caused by mutations in Cu/Zn-superoxide dismutase (SOD1), altered solubility and aggregation of the mutant protein implicates failure of pathways for detecting and catabolizing misfolded proteins. Our previous studies demonstrated early reduction of proteasome-mediated proteolytic activity in lumbar spinal cord of SOD1(G93A) transgenic mice, tissue particularly vulnerable to disease. The purpose of this study was to identify any underlying abnormalities in proteasomal structure. In lumbar spinal cord of pre-symptomatic mice [postnatal day 45 (P45) and P75], normal levels of structural 20S alpha subunits were incorporated into 20S/26S proteasomes; however, proteasomal complexes separated by native gel electrophoresis showed decreased immunoreactivity with antibodies to beta3, a structural subunit of the 20S proteasome core, and beta5, the subunit with chymotrypsin-like activity. This occurred prior to increase in beta5i immunoproteasomal subunit. mRNA levels were maintained and no association of mutant SOD1 with proteasomes was identified, implicating post-transcriptional mechanisms. mRNAs also were maintained in laser captured motor neurons at a later stage of disease (P100) in which multiple 20S proteins are reduced relative to the surrounding neuropil. Increase in detergent-insoluble, ubiquitinated proteins at P75 provided further evidence of stress on mechanisms of protein quality control in multiple cell types prior to significant motor neuron death.
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PMID:Proteasomes remain intact, but show early focal alteration in their composition in a mouse model of amyotrophic lateral sclerosis. 1831 58

Liposomes are phospholipid vesicles that have been used as carriers of antigens and adjuvants. Lipid A, the endotoxic moiety of Gram-negative bacterial lipopolysaccharide is a potent adjuvant and incorporation into liposomes essentially reduces the endotoxic activity of lipid A. In this study, we analyzed the effect of liposomal lipid A [L(LA)] on the MHC class I antigen processing machinery in murine antigen presenting cells (APCs). L(LA) enhanced the surface expression of MHC class I, class II, CD80, and CD86 molecules, induced the secretion of IFN-gamma, IL-12p40, TNF-alpha and IL-10, and caused a shift in the proteasome profile from constitutive to immunoproteasomes as observed by the induction of beta2i, beta5i, PA28alpha, and PA28beta subunits. L(LA) acts through the production of IFN-gamma as demonstrated with APCs generated from IFN-gamma knockout mice. L(LA) therefore appears to act as an intracellular adjuvant by upregulating the antigen processing machinery, which could result in efficient antigen presentation.
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PMID:Modulation of immunoproteasome subunits by liposomal lipid A. 1845 79

The 26S proteasome is the executing protease of the ubiquitin-dependent degradation system. It consists of one or two 19S regulatory sub-complexes and one 20S proteolytic sub-complex (1). The 20S proteasome is a barrel-shaped cylinder which consists or four stacked rings (2). Each of the two outer rings consists of seven different alpha-subunits, whereas each of the two inner rings is formed by seven different beta-subunits (3). Only three of these beta-subunits bear a catalytically active N-terminal threonine (4,5). Under normal conditions, these are beta1 (delta), beta2 (Z), and beta5 (mb1). However, by induction of some cytokines, e.g., interferon-gamma, these subunits are exchanged against beta1i(LMP2), beta2i (Mecl1), and beta5i (LMP7) and the so-called immunoproteasome is formed (6,7). To investigate the role of LMP7 in MHC class I-restricted immunology, we decided to generate a transgenic mouse which constitutively expresses LMP7 in all tissues. To get the highest possible expression, we bread the mice to be homozygous for the transgene LMP7. These mice cannot be identified by conventional polymerase chain reaction (PCR). So far, Southern blotting was the only possible method to quantify the DNA content. Here, we describe the analysis of these mice by quantitative PCR using sequence specific fluorescence resonance energy transfer-primers to reliably detect a difference in DNA content as small as a factor of 2 or only one PCR cycle.
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PMID:Identification of homozygous transgenic mice by genomic real-time PCR. 1869 58

Molecular docking of small ligands to biologically active macromolecules has become a valuable strategy to predict the stability of complexes between potential partners and their binding modes. In this perspective, we applied this computational procedure to rationalize the reported role of polyphenols as inhibitors of the mammalian 20S proteasomes. In particular, polyphenols were shown to modulate each proteasomal activity at different extents both in the constitutive and the inducible enzyme. We performed a flexible molecular docking analysis between a set of polyphenols previously demonstrated to have the highest binding affinity and both the constitutive (from deposited PDB structures) and homology modeled active subunits of the IFN-gamma inducible proteasome, to provide insight into the possible mechanism of interaction. Among the tested polyphenols, (-)-epigallocatechin-3-gallate showed the highest affinity for the proteasome subunits, both in terms of intermolecular energy and predicted equilibrium constants, in particular for beta5 and beta5i subunits (E(total) = -66 kcal/mol, Ki = 81.3 microM and E(Total) = -83.9 kcal/mol, Ki = 0.29 microM, respectively), known to be related to the chymotrypsin-like and BrAAP activities. Collectively, polyphenols showed a higher affinity for the inducible subunits, in agreement with previous in vitro studies. Additionally, different contributions to the interaction energy (van der Waals, electrostatic, H-bond) of proteasome-polyphenols complexes were dissected.
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PMID:Homology modeling and docking analysis of the interaction between polyphenols and mammalian 20S proteasomes. 1943 41

In the last years, intracellular protein degradation by the proteasome has become a focus area of scientific interest. Here, we describe a proteomics approach for the molecular mapping of the constituents of the proteolytically active core particle, the constitutive 20S proteasome from mouse intestine. In addition to the proteomics workflow widely used for protein isolation, gel electrophoretic separation, in-gel digestion, and UV-MALDI mass spectrometry, high-resolution Fourier transform ion cyclotron resonance mass spectrometry using infrared-MALDI ionisation (IR-MALDI FTICR-MS) has been employed as an efficient method for protein identification by peptide mass fingerprint. The 20S proteasome subunits alpha1-alpha7 and beta1-beta7 were completely and unambiguously identified. In addition to subunits beta1 and beta2, the corresponding inducible subunits being part of the immuno-proteasome were identified. The subunit beta5i was found to completely replace the corresponding constitutive subunit, suggesting a high proteolytic activity of the intestinal proteasome leading to increased production of antigenic peptides. The high mass accuracy in the low ppm range and resolution of FTICR-MS provide direct identifications of individual proteins as mixtures such as components resulting from incomplete electrophoretic separation. In addition, the comparison of UV- and IR-MALDI FTICR-MS may provide details of fragmentation and rearrangement reactions that may occur under UV-MALDI ionisation conditions.
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PMID:Identification of the molecular composition of the 20S proteasome of mouse intestine by high-resolution mass spectrometric proteome analysis. 1954 23

Dysfunction of the ubiquitin-proteasome system (UPS) occurs in dopaminergic neurones in the SN in PD and it is associated with Lewy body formation. However, it remains unknown whether this is specific to PD or whether it also occurs in multiple system atrophy (MSA) and progressive supranuclear palsy (PSP) where nigral dopaminergic neurones also degenerate. In the present study, we investigated changes in the expression of proteasomal subunits in the SN in PD, MSA and PSP. Immunohistochemistry double staining showed that proteasome 20S-alpha4 and -alpha6, and 20S-beta3 and -beta5i subunits are colocalized with tyrosine hydroxylase (TH)-positive cells in the SN of control, PD, MSA and PSP brain. Semi-quantitative analysis showed a significant loss of 20S-alpha4 and -alpha6 subunits TH-positive cells in PD, MSA and PSP compared to control tissue. There was no change in the expression of 20S-beta3 and -beta5i subunits in any of the disease states. The expression of PA700-Rpt5 subunits was not changed in PSP or PD but was significantly increased in MSA compared to control SN. PA700-Rpn10 subunit was not colocalized with TH within dopamine cells but was co-expressed with glial fibrillary acid protein (GFAP) positive astrocytes in the SN of all groups. PA28-alpha immunoreactivity was low in TH positive neurones in control tissue and quantification was not possible. Qualitative analysis suggested a decrease in PD and no immunoreactivity was detected in MSA or PSP. The results show that changes in proteasomal structure occur in the SN in PD, MSA and PSP and that these are similar in nature suggesting that dysfunction of UPS is not specific to PD or to Lewy body formation.
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PMID:A comparison of changes in proteasomal subunit expression in the substantia nigra in Parkinson's disease, multiple system atrophy and progressive supranuclear palsy. 2017 3


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