Peptidases trimming MHC class I ligands

Area of Science:

• Immunology
• Molecular Biology
• Proteomics

Background:

• MHC class I molecules present peptides derived from intracellular antigens.
• Peptide generation involves proteasomal degradation and subsequent trimming by exopeptidases.
• The roles of specific exopeptidases in antigen processing and presentation are still being elucidated.

Purpose of the Study:

• To investigate the contribution of various exopeptidases to the generation of peptides presented by MHC class I molecules.
• To understand how different peptidases influence the repertoire of MHC class I ligands.
• To explore the impact of exopeptidase activity on immune surveillance by T cells and NK cells.

Main Methods:

• Analysis of peptide pools presented by MHC class I molecules from cells with genetic deficiencies in specific exopeptidases.
• Mass spectrometry-based identification and quantification of MHC-bound peptides.
• Functional assays assessing T cell and NK cell recognition of target cells.

Main Results:

• Endoplasmic reticulum aminopeptidases significantly influence the repertoire of peptides presented by MHC class I molecules.
• Cytosolic peptidases have a neutral or degradative effect on MHC ligands.
• Deficiency in specific endoplasmic reticulum aminopeptidases can lead to altered immune recognition.
• Insulin-regulated aminopeptidase is identified as the key endosomal trimming peptidase for cross-presented antigens.

Conclusions:

• Exopeptidases, particularly those in the endoplasmic reticulum, play a critical role in shaping the MHC class I peptide repertoire.
• Targeting these peptidases could modulate immune responses.
• Understanding endosomal antigen processing is vital for effective cross-presentation-based immunotherapies.