Placental leucine aminopeptidase efficiently generates mature antigenic peptides in vitro but in patterns distinct from endoplasmic reticulum aminopeptidase 1

Protein Chemistry Laboratory, Institute of Radioisotopes and Radiodiagnostic Products, National Centre for Scientific Research "Demokritos," Athens 15310, Greece.
The Journal of Immunology (Impact Factor: 5.36). 08/2010; 185(3):1584-92. DOI: 10.4049/jimmunol.0902502
Source: PubMed

ABSTRACT All three members of the oxytocinase subfamily of M1 aminopeptidases, endoplasmic reticulum aminopeptidase 1 (ERAP1), ERAP2, and placental leucine aminopeptidase (PLAP), also known as insulin-regulated aminopeptidase, have been implicated in the generation of MHC class I-presented peptides. ERAP1 and 2 trim peptides in the endoplasmic reticulum for direct presentation, whereas PLAP has been recently implicated in cross-presentation. The best characterized member of the family, ERAP1, has unique enzymatic properties that fit well with its role in Ag processing. ERAP1 can trim a large variety of long peptide sequences and efficiently accumulate mature antigenic epitopes of 8-9 aa long. In this study, we evaluate the ability of PLAP to process antigenic peptide precursors in vitro and compare it with ERAP1. We find that, similar to ERAP1, PLAP can trim a variety of long peptide sequences efficiently and, in most cases, accumulates appreciable amounts of correct length mature antigenic epitope. Again, similar to ERAP1, PLAP continued trimming some of the epitopes tested and accumulated smaller products effectively destroying the epitope. However, the intermediate accumulation properties of ERAP1 and PLAP are distinct and epitope dependent, suggesting that these two enzymes may impose different selective pressures on epitope generation. Overall, although PLAP has the necessary enzymatic properties to participate in generating or destroying MHC class I-presented peptides, its trimming behavior is distinct from that of ERAP1, something that supports a separate role for these two enzymes in Ag processing.

Download full-text


Available from: Efstratios Stratikos, Aug 15, 2015
  • Source
    • "Close family members to IRAP, endoplasmic reticulum aminopeptidase 1 and 2 (ERAP1, ERAP2), were identified as enzymes involved in the generation of mature antigenic epitopes from peptide precursors that are delivered into the ER by a transporter associated with antigen processing (Saveanu et al., 2005). Recently, IRAP has also been implicated in the generation of antigenic peptide for cross-presentation, not in the ER but in endosomal compartments (Saveanu et al., 2009) (Segura et al., 2009) and in patterns that are distinct from those processed by the ERAPs (Georgiadou et al., 2010). Therefore, not only has a new function for IRAP been discovered but also the peptide substrate specificity is significantly broader than previously proposed (Albiston et al., 2007). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Two structurally distinct peptides, angiotensin IV and LVV-haemorphin 7, both competitive high-affinity inhibitors of insulin-regulated aminopeptidase (IRAP), were found to enhance aversion-associated and spatial memory in normal rats and to improve performance in a number of memory tasks in rat deficits models. These findings provide compelling support for the development of specific, high-affinity inhibitors of the enzyme as new cognitive enhancing agents. Different classes of IRAP inhibitors have been developed including peptidomimetics and small molecular weight compounds identified through in silico screening with a homology model of the catalytic domain of IRAP. The proof of principal that inhibition of IRAP activity results in facilitation of memory has been obtained by the demonstration that the small-molecule IRAP inhibitors also exhibit memory-enhancing properties.
    British Journal of Pharmacology 08/2011; 164(1):37 - 47. DOI:10.1111/j.1476-5381.2011.01402.x · 4.99 Impact Factor
  • Source
    • "The increase in IRAP in tumour cells was concurrent with increases in GLUT4, the insulin receptor and AKT phosphorylation (Shibata et al., 2007). The endoplasmic reticulum aminopeptidases, ERAP1 (adipocyte-derived leucine aminopeptidase) and ERAP2 (leukocyte-derived arginine aminopeptidase), form a heterodimer and are involved in post-proteosome processing generation of HLA class I antigenic peptides in immune response (Goldberg et al., 2002; Saveanu et al., 2005), and is not redundant with post-proteosome antigen processing of some IRAP endosomal populations (Goldberg et al., 2002; Georgiadou et al., 2010). In addition, ERAP1 and 2 appear to have a role in pathogenesis of ankylosing spondylitis, and ERAP1 has been implicated in shedding of cytokine receptors from the cell surface to attenuate signalling (reviewed in Haroon and Inman, 2010). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Metallopeptidases of the M1 family are found in all phyla (except viruses) and are important in the cell cycle and normal growth and development. M1s often have spatiotemporal expression patterns which allow for strict regulation of activity. Mutations in the genes encoding M1s result in disease and are often lethal. This family of zinc metallopeptidases all share the catalytic region containing a signature amino acid exopeptidase (GXMXN) and a zinc binding (HEXXH[18X]E) motif. In addition, M1 aminopeptidases often also contain additional membrane association and/or protein interaction motifs. These protein interaction domains may function independently of M1 enzymatic activity and can contribute to multifunctionality of the proteins. A brief review of M1 metalloproteases in plants and animals and their roles in the cell cycle is presented. In animals, human puromycin-sensitive aminopeptidase (PSA) acts during mitosis and perhaps meiosis, while the insect homologue puromycin-sensitive aminopeptidase (PAM-1) is required for meiotic and mitotic exit; the remaining human M1 family members appear to play a direct or indirect role in mitosis/cell proliferation. In plants, meiotic prophase aminopeptidase 1 (MPA1) is essential for the first steps in meiosis, and aminopeptidase M1 (APM1) appears to be important in mitosis and cell division. M1 metalloprotease activity in the cell cycle is conserved across phyla. The activities of the multifunctional M1s, processing small peptides and peptide hormones and contributing to protein trafficking and signal transduction processes, either directly or indirectly impact on the cell cycle. Identification of peptide substrates and interacting protein partners is required to understand M1 function in fertility and normal growth and development in plants.
    Annals of Botany 05/2011; 107(7):1171-81. DOI:10.1093/aob/mcq265 · 3.30 Impact Factor
  • Source
    • "Recent work by the group of Peter Van Endert identified IRAP as an endosomespecific peptidase required for such peptide-trimming in crosspresentation (Saveanu et al., 2009). IRAP, which is specifically targeted toward endosomes by its amino-terminal cytoplasmic tail (Hou et al., 2006), displays a broader pH optimum compared to ERAP, allowing IRAP activity at a slightly acidic endosomal pH (Georgiadou et al., 2010). IRAP activity might ensure that antigen-derived peptides, which were generated by proteasomal degradation in the cytoplasm and re-imported into the endosomes by endosomal TAP, are trimmed to their optimal size for loading on MHC I molecules, providing potent cross-presentation by the phagosome-to-cytosol pathway. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Antigen cross-presentation enables dendritic cells (DCs) to present extracellular antigens on major histocompatibility complex (MHC) I molecules, a process that plays an important role in the induction of immune responses against viruses and tumors and in the induction of peripheral tolerance. In order to allow intracellular processing for cross-presentation, internalized antigens are targeted by distinct endocytic receptors toward specific endosomal compartments, where they are protected from rapid lysosomal degradation. From these compartments, antigens are processed for loading onto MHC I molecules. Such processing generally includes antigen transport into the cytoplasm, a process that is regulated by members of the ER-associated degradation (ERAD) machinery. After proteasomal degradation in the cytoplasm, antigen-derived peptides have been shown to be re-imported into the same endosomal compartment by endosomal transporter associated with antigen processing, another ER protein, which is recruited toward the endosomes after DC maturation. In our review, we highlight the recent advances on the molecular mechanisms of cross-presentation. We focus on the necessity of such antigen storage compartments and point out important parallels to MHC I-restricted presentation of endogenous antigens. We discuss the composition of such endosomes and the targeting of extracellular antigens into this compartment by specific endocytic receptors. Finally, we highlight recent advances on the recruitment of the cross-presentation machinery, like the members of the MHC I loading complex and the ERAD machinery, from the ER toward these storage compartments, a process that can be induced by antigen encounter or by activation of the dendritic cell after contact with endotoxins.
    Frontiers in Immunology 01/2011; 2:87. DOI:10.3389/fimmu.2011.00087
Show more

Similar Publications