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Updated: Jun 25, 2025

Use of Single Chain MHC Technology to Investigate Co-agonism in Human CD8+ T Cell Activation
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Use of Single Chain MHC Technology to Investigate Co-agonism in Human CD8+ T Cell Activation

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Dual role of the peptide-loading complex as proofreader and limiter of MHC-I presentation

Jamina Brunnberg1, Martina Barends1, Stefan Frühschulz1

  • 1Institute of Biochemistry, Biocenter, Goethe University Frankfurt, Frankfurt am Main 60438, Germany.

Proceedings of the National Academy of Sciences of the United States of America
|May 21, 2024
PubMed

Insights

The peptide-loading complex (PLC) editing module components, like tapasin, limit abundant peptides and proofread peptide-MHC-I (pMHC-I) complexes, ensuring diverse antigen presentation for immune surveillance.

Area of Science:

  • Immunology
  • Molecular Biology
  • Cellular Biology

Background:

  • Antigen presentation by MHC-I is crucial for adaptive immunity.
  • The peptide-loading complex (PLC) is key for peptide translocation, loading, and proofreading.
  • The specific roles of individual PLC components in shaping the presented peptide repertoire are not fully understood.

Purpose of the Study:

  • To investigate the impact of individual PLC components on the surface presentation of peptide-MHC-I (pMHC-I) complexes.
  • To quantify MHC-I allomorphs and defined pMHC-I complexes using advanced antibody-nanobody and soluble T cell receptor (sTCR) technologies.

Main Methods:

  • Utilized stoichiometrically defined antibody-nanobody complexes for MHC-I allomorph quantification.
  • Employed engineered soluble T cell receptors (sTCRs) to quantify specific pMHC-I complexes.
  • Performed knockouts of PLC editing module components (tapasin, ERp57, calreticulin) to assess their effects.

Main Results:

  • Knocking out PLC editing components altered MHC-I surface composition, reducing HLA-A*02:01 presentation and increasing HLA-B*40:01.
  • These knockouts enhanced presentation of suboptimal HLA-A*02:01 complexes.
  • Elevated presentation of high-affinity cytosolic peptides was observed following knockouts.

Conclusions:

  • PLC editing module components have a dual role: peptide proofreading and limiting abundant peptide presentation.
  • This dual function is essential for maintaining a broad spectrum of antigenic peptides presented on the cell surface.
  • Understanding these roles provides insights into immune surveillance mechanisms.

Keywords:
T cell receptorantigen processingpeptide-loading complextransporter associated with antigen processing TAPtumor-associated antigen

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