Search results for "peptidase"

Characterizing the N-terminal processing motif of MHC class I ligands.

2008

Abstract Most peptide ligands presented by MHC class I molecules are the product of an intracellular pathway comprising protein breakdown in the cytosol, transport into the endoplasmic reticulum, and successive N-terminal trimming events. The efficiency of each of these processes depends on the amino acid sequence of the presented ligand and its precursors. Thus, relating the amino acid composition N-terminal of presented ligands to the sequence specificity of processes in the pathway gives insight into the usage of ligand precursors in vivo. Examining the amino acid composition upstream the true N terminus of MHC class I ligands, we demonstrate the existence of a distinct N-terminal proces…

Features of TAP-independent MHC class I ligands revealed by quantitative mass spectrometry.

2008

TAP is responsible for transferring cytosolic peptides into the ER, where they can be loaded onto MHC molecules. Deletion of TAP results in a drastic reduction of MHC class I surface expression and alters the presented peptide pattern. This key molecule in antigen processing is tackled by several viruses and lost in some tumors, rendering the altered cells less vulnerable to T cell-based immune surveillance. Using the TAP-deficient cell line LCL721.174 and its TAP-expressing progenitor cell line LCL721.45, we identified and quantified more than 160 HLA ligands, 50 of which were presented TAP-independently. Peptides which were predominantly presented on the TAP-deficient LCL721.174 cell line…

Priming of Leishmania-Reactive CD8+ T cells In Vivo Does Not Require LMP7-Containing Immunoproteasomes

2012

Relative contribution of different l-arginine sources to the substrate supply of endothelial nitric oxide synthase

2011

In certain cases of endothelial dysfunction l-arginine becomes rate-limiting for NO synthesis in spite of sufficiently high plasma concentrations of the amino acid. To better understand this phenomenon, we investigated routes of substrate supply to endothelial nitric oxide synthase (eNOS). Our previous data with human umbilical vein (HUVEC) and EA.hy.926 endothelial cells demonstrated that eNOS can obtain its substrate from the conversion of l-citrulline to l-arginine and from protein breakdown. In the present study, we determined the quantitative contribution of proteasomal and lysosomal protein degradation and investigated to what extent extracellular peptides and l-citrulline can provide…

Proteasomes shape the repertoire of T cells participating in antigen-specific immune responses

2006

Differences in the cleavage specificities of constitutive proteasomes and immunoproteasomes significantly affect the generation of MHC class I ligands and therefore the activation of CD8-positive T cells. Based on these findings, we investigated whether proteasomal specificity also influences CD8-positive T cells during thymic selection by peptides derived from self proteins. We find that one of the self peptides responsible for positive selection of ovalbumin-specific OT-1 T cells, which is derived from the f-actin capping protein (Cpalpha1), is efficiently generated only by immunoproteasomes. Furthermore, OT-1 mice backcrossed onto low molecular mass protein 7 (LMP7)-deficient mice show a…

Development of Novel Selective Peptidomimetics Containing a Boronic Acid Moiety, Targeting the 20S Proteasome as Anticancer Agents

2014

This paper describes the design, synthesis, and biological evaluation of peptidomimetic boronates as inhibitors of the 20S proteasome, a validated target in the treatment of multiple myeloma. The synthesized compounds showed a good inhibitory profile against the ChT-L activity of 20S proteasome. Compounds bearing a β-alanine residue at the P2 position were the most active, that is, 3-ethylphenylamino and 4-methoxyphenylamino (R)-1-{3-[4-(substituted)-2-oxopyridin-1(2H)-yl]propanamido}-3-methylbutylboronic acids (3 c and 3 d, respectively), and these derivatives showed inhibition constants (Ki ) of 17 and 20 nM, respectively. In addition, they co-inhibited post glutamyl peptide hydrolase act…

Quantitative Analysis of Prion-Protein Degradation by Constitutive and Immuno-20S Proteasomes Indicates Differences Correlated with Disease Susceptib…

2004

Abstract The main part of cytosolic protein degradation depends on the ubiquitin-proteasome system. Proteasomes degrade their substrates into small peptide fragments, some of which are translocated into the endoplasmatic reticulum and loaded onto MHC class I molecules, which are then transported to the cell surface for inspection by CTL. A reliable prediction of proteasomal cleavages in a given protein for the identification of CTL epitopes would benefit immensely from additional cleavage data for the training of prediction algorithms. To increase the knowledge about proteasomal specificity and to gain more insight into the relation of proteasomal activity and susceptibility to prion diseas…

Optimization of peptidomimetic boronates bearing a P3 bicyclic scaffold as proteasome inhibitors

2014

Abstract A new series of pseudopeptide boronate proteasome inhibitors (2–3) was developed, through optimization of our previously described analogs of bortezomib, bearing a bicyclic 1,6-naphthyridin-5(6H)-one scaffold as P3 fragment (1). The biological evaluation on human 20S proteasome displayed a promising inhibition profile, especially for compounds bearing a P2 ethylene fragment, which exhibited Ki values in the nanomolar range for the ChT-L activity (e.g. 2a, Ki = 0.057 μM) and considerable selectivity for proteasome over bovine pancreatic α-chymotrypsin. Docking experiments into the yeast 20S proteasome revealed that the ligands are accommodated predominantly into the ChT-L site and t…

SUMOylation of Blimp-1 promotes its proteasomal degradation

2011

Abstract B lymphocyte induced maturation protein-1 (Blimp-1) is a transcription repressor of the Krueppel-like family. Blimp-1 plays important roles in developmental processes, such as of germ cells and hair follicle stem cells. In B lymphocytes Blimp-1 orchestrates the terminal differentiation into plasma cells. We discovered that Blimp-1 undergoes SUMOylation by SUMO-1. This SUMOylation is modulated by the SUMO protease SENP1. While Blimp-1 is relatively stable in 293T cells, a fusion with SUMO1 rendered it to rapid proteasomal degradation. Increase in SENP1 activity stabilized Blimp-1, while a decrease promoted its degradation. Our data indicate that SUMOylation of Blimp-1 regulates its …

Immunoproteasome and Non-Covalent Inhibition: Exploration by Advanced Molecular Dynamics and Docking Methods

2021

The selective inhibition of immunoproteasome is a valuable strategy to treat autoimmune, inflammatory diseases, and hematologic malignancies. Recently, a new series of amide derivatives as non-covalent inhibitors of the β1i subunit with Ki values in the low/submicromolar ranges have been identified. Here, we investigated the binding mechanism of the most potent and selective inhibitor, N-benzyl-2-(2-oxopyridin-1(2H)-yl)propanamide (1), to elucidate the steps from the ligand entrance into the binding pocket to the ligand-induced conformational changes. We carried out a total of 400 ns of MD-binding analyses, followed by 200 ns of plain MD. The trajectories clustering allowed identifying thre…