IRAP Identifies an Endosomal Compartment Required for MHC Class I Cross-Presentation

Saveanu, Loredana; Carroll, Oliver; Weimershaus, Mirjana; Guermonprez, Pierre; Firat, Elke; Lindo, Vivian; Greer, Fiona; Davoust, Jean; Kratzer, Roland; Keller, Susanna R.; Niedermann, Gabriele; Endert, Peter Van

doi:10.1126/science.1172845

Cited by 238 publications

(260 citation statements)

References 23 publications

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“…IRAP contains the canonical zinc-binding amino acid motif HELAH, which is essential for the enzymatic activity 26 . A form of IRAP in which the HELAH sequence was changed into HALAH (E465A substitution) co-localized, like the wild-type protein, with syntaxin 6 (Stx6), a SNARE of IRAP + endosomes 16,17 (Fig. 4a).…”

Section: Irap Enzymatic Activity Is Not Involved In Tlr9 Activationmentioning

confidence: 99%

“…presence of the aminopeptidase IRAP (Insulin Responsive AminoPeptidase), a type II transmembrane protein composed of a catalytic site localized in the endosomal lumen and a cytosolic domain of 110 amino acids. In DCs, IRAP + endosomes are rapidly recruited to DC phagosomes, where the enzymatic activity of IRAP is involved in antigen processing during MHC-I cross-presentation 16,17 .…”

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IRAP+ endosomes restrict TLR9 activation and signaling

et al. 2017

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Retention of intracellular Toll-Like Receptors (TLRs) in the endoplasmic reticulum prevents their activation under basal conditions. TLR9 is activated by sensing ligands in specific endosomal/lysosomal compartments. Here, we describe the identification of insulin responsive aminopeptidase (IRAP) endosomes as major cellular compartments for the early steps of TLR9 activation in dendritic cells (DCs). Both TLR9 and its ligand CpG were found as cargo in IRAP endosomes. In the absence of IRAP, CpG and TLR9 trafficking to lysosomes and TLR9 signaling were enhanced in DCs and in mice following bacterial infection. IRAP stabilized CpG-containing endosomes by interacting with the actin nucleation factor FHOD4, slowing down TLR9 trafficking towards lysosomes. Thus, endosome retention of TLR9 via IRAP interaction with the actin cytoskeleton is a mechanism that prevents TLR9hyper-activation in DCs. discriminate between different classes of microbial products and initiate specific signaling cascades. While microbial products with no equivalent in mammalian cells, such as the components of the bacterial wall, are recognized by surface TLRs (1, 2, 4, 5 and 6), pathogen derived nucleic acids are sensed by intracellular TLRs (3,7, 8 and 9). Recognition of nucleic acids by intracellular TLRs has the potential to trigger autoimmune diseases through interaction with self nucleic acids 1 . To avoid inappropriate activation of endosomal TLRs, their trafficking is tightly controlled. Thus, in basal conditions the receptors are located in the endoplasmic reticulum (ER) and translocate to endocytic vesicles only after cell stimulation by TLR ligands. Although all intracellular TLRs reside in the ER 2,3 , the trafficking pathways that move the receptors into the endocytic pathway show considerable variation among intracellular TLRs 4-6 . For example, TLR7 traffics from Golgi stacks directly to endosomes using the clathrin adaptor AP4, whereas the TLR9 is directed to the cell surface and reaches the endosomes via AP2-mediated clathrin-dependent endocytosis 6 .In addition to the transfer into the endocytic pathway, a second step that controls the activation of endosomal TLRs is their partial proteolysis by an array of different proteases, specific for each TLR 5,7-12 .Although less often mentioned, the intracellular trafficking of its ligand also controls the activation of TLR9. TLR9 ligands (CpG) are internalized via clathrin-mediated endocytosis in early endosomes and translocate to late LAMP + compartments 2 . TLR9 activation depends on CpG localization, since the abrogation of CpG translocation to LAMP + compartments by specific inhibitors decreased TLR9 signaling 13,14 . Thus, the intracellular trafficking of both, the ligand and the receptor are essential for the control of TLR9 activation. RESULTS IRAP deletion increases TLR9 responseTo address the role of IRAP in TLRs signaling, wild-type and IRAP-deficient bone marrow derived dendritic cells (BMDCs) were stimulated with specific TLR ligands: polyIC for TLR3, Imiquimod fo...

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Section: Irap Enzymatic Activity Is Not Involved In Tlr9 Activationmentioning

confidence: 99%

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confidence: 99%

IRAP+ endosomes restrict TLR9 activation and signaling

et al. 2017

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“…In the ER, epitope precursor peptides imported by TAP are trimmed by ER aminopeptidases (ERAPs), whereas insulinregulated aminopeptidase, a closely related enzyme residing in endosomes, exerts an equivalent function on cross-presented Ags of extracellular origin (3,4). Although rodents express a single ERAP enzyme, human cells harbor two, ERAP1 and ERAP2 (5).…”

Section: P Rocessing Of Ags For Presentation By Mhc Proteins Involvesmentioning

confidence: 99%

ERAP1–ERAP2 Dimerization Increases Peptide-Trimming Efficiency

Evnouchidou

Weimershaus

Saveanu

et al. 2014

The Journal of Immunology

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The endoplasmic reticulum aminopeptidases (ERAP)1 and ERAP2 play a critical role in the production of final epitopes presented by MHC class I molecules. Formation of heterodimers by ERAP1 and ERAP2 has been proposed to facilitate trimming of epitope precursor peptides, but the effects of dimerization on ERAP function remain unknown. In this study, we produced stabilized ERAP1–ERAP2 heterodimers and found that they produced several mature epitopes more efficiently than a mix of the two enzymes unable to dimerize. Physical interaction with ERAP2 changes basic enzymatic parameters of ERAP1 and improves its substrate-binding affinity. Thus, by bringing the two enzymes in proximity and by producing allosteric effects on ERAP1, dimerization of ERAP1/2 creates complexes with superior peptide-trimming efficacy. Such complexes are likely to enhance Ag presentation by cells displaying coordinated expression of the two enzymes.

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“…1,24 Cross-presentation by dendritic cells can proceed by at least two separate biochemical pathways, only one of which is dependent on ERAP1 enzymatic activity. 25 To test whether thimerosal can affect ERAP1-dependent antigen presentation in live cells we incubated ERAP +/+ and ERAP −/− BMDCs (bone marrow derived dendritic cells) with a fixed dose of ovalbumin (OVA) and increasing dosages of the inhibitor and then exposed them to transgenic OT-I CD8+ T cells as described in the methods section. Antigen crosspresentation to CD8+ T cells was quantified by measuring the IL-2 secretion by OT-I T cells, reflecting their activation.…”

Section: E Ndoplasmic Reticulum (Er) Aminopeptidases Generatementioning

confidence: 99%

Screening Identifies Thimerosal as a Selective Inhibitor of Endoplasmic Reticulum Aminopeptidase 1

Stamogiannos

Papakyriakou

Mauvais

et al. 2016

ACS Med. Chem. Lett.

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We employed virtual screening followed by in vitro evaluation to discover novel inhibitors of ER aminopeptidase 1, an important enzyme for the human adaptive immune response that has emerged as an attractive target for cancer immunotherapy and the control of autoimmunity. Screening hits included three structurally related compounds carrying the (E)-N′-((1H-indol-3-yl)methylene)-1H-pyrazole-5-carbohydrazide scaffold and (2-carboxylatophenyl)sulfanyl-ethylmercury as novel ERAP1 inhibitors. The latter, also known as thimerosal, a common component in vaccines, was found to inhibit ERAP1 in the submicromolar range and to present strong selectivity versus the homologous aminopeptidases ERAP2 and IRAP. Cell-based analysis indicated that thimerosal can effectively reduce ERAP1-dependent cross-presentation by dendritic cells in a dose-dependent manner.

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IRAP Identifies an Endosomal Compartment Required for MHC Class I Cross-Presentation

Cited by 238 publications

References 23 publications

IRAP+ endosomes restrict TLR9 activation and signaling

IRAP+ endosomes restrict TLR9 activation and signaling

ERAP1–ERAP2 Dimerization Increases Peptide-Trimming Efficiency

Screening Identifies Thimerosal as a Selective Inhibitor of Endoplasmic Reticulum Aminopeptidase 1

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