# ER-aminopeptidases: Conformational regulation and antigen presentation function

> **NIH NIH R01** · UNIV OF MASSACHUSETTS MED SCH WORCESTER · 2020 · $502,500

## Abstract

PROJECT SUMMARY/ABSTRACT
ERAP1, ERAP2, and IRAP are M1-family zinc aminopeptidases with important roles in trimming antigenic
peptide precursors for loading onto MHC-I proteins. Common polymorphisms in the erap1 gene are associated
with increased susceptibility to autoimmune diseases including ankylosing spondylitis, psoriasis, Behçet's
disease, and birdshot retinopathy, increased susceptibility to certain kinds of cancer, and essential hypertension.
Polymorphic residues are located distal to the enzyme active site, and the mechanism underlying their effects
on enzymatic activity is unknown. ERAP2 polymorphisms are less common and more weakly associated with
autoimmune diseases than for ERAP1. Key questions about ER aminopeptidases include their mechanism of
action, in particular the mechanistic basis for the unique length-dependent cleavage activity, the nature of the
linkage of polymorphic variants with autoimmune disease, and to what degree mechanistic insights about ERAP1
can be extended to the other members of the oxytocinase subfamily ERAP2 and IRAP. An overarching
hypothesis of this proposal is that large-scale conformational alterations provide a mechanistic underpinning for
the effects of ER aminopeptidase polymorphisms on enzymatic activity and disease association, and that the
conformational equilibria are modulated by interactions with other proteins in the endoplasmic reticulum. One
specific aim of the proposed research is to understand how interactions between ER aminopeptidase domains
regulate enzyme activity. A detailed mechanistic model for ERAP1 catalytic mechanism will be developed and
tested. The model couples ERAP1 binding interactions near the N- and C-termini of peptide substrates with
large-scale domain closure motions that stabilize the catalytically active configuration of key active site residues.
Using salt-bridge mutations known to alter ERAP1 conformational dynamics, and small-molecule inhibitors that
alter ERAP1 conformational equilibria, we will test whether disease-associated polymorphisms act through
differential stabilization of open and closed conformers, and we will determine whether ERAP2 and IRAP
similarly utilize large-scale domain closure motions to regulate enzymatic activity. A second specific aim is to
determine the structural basis and functional consequences of ERp44-mediated endoplasmic reticulum retention
of ERAP1 and ERAP2. We aim to determine structures of complexes of ERp44 with ERAP1 and ERAP2, to
characterize the effect of ERp44 interaction on ERAP1 and ERAP2 processing, and to evaluate the role of
ERAP1-ERp44 interactions in generating new epitopes under ER stress. A third specific aim is to evaluate the
influence of the ER chaperones tapsin and TAPBPR on ERAP1 trimming of epitope precursors while they are
bound to MHC-I.
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## Key facts

- **NIH application ID:** 10045425
- **Project number:** 1R01AI153828-01
- **Recipient organization:** UNIV OF MASSACHUSETTS MED SCH WORCESTER
- **Principal Investigator:** Lawrence J. Stern
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $502,500
- **Award type:** 1
- **Project period:** 2020-08-07 → 2024-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10045425

## Citation

> US National Institutes of Health, RePORTER application 10045425, ER-aminopeptidases: Conformational regulation and antigen presentation function (1R01AI153828-01). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10045425. Licensed CC0.

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