Folded or Degraded in Endoplasmic Reticulum.

Area of Science:

• Cell Biology
• Immunology
• Protein Chemistry

Background:

• Immune checkpoint proteins, like other secretory proteins, require endoplasmic reticulum (ER) processing for correct folding and function.
• The ER employs chaperones, enzymes, and quality control systems to ensure proper protein maturation and trafficking.
• Dysfunctional ER leads to ER stress and the unfolded protein response (UPR), impacting cellular health.

Purpose of the Study:

• To review the endoplasmic reticulum processing, including glycosylation, folding, and transport, of immune checkpoint proteins.
• To discuss the ER quality control mechanisms governing the fate of these critical immune proteins.
• To explore the link between ER stress, protein degradation pathways, and potential immunotherapeutic strategies.

Main Methods:

• Literature review of endoplasmic reticulum protein processing.
• Analysis of immune checkpoint protein maturation pathways.
• Examination of ER quality control, ER-associated degradation (ERAD), and ER-to-lysosomes-associated degradation (ERLAD) mechanisms.
• Review of unfolded protein response (UPR) and ER stress.

Main Results:

• Immune checkpoint proteins undergo intricate folding, glycosylation, and quality control within the ER.
• The ER quality control system ensures proper protein folding, directing correctly folded proteins for transport via COPII vesicles and misfolded proteins for degradation.
• ER stress and UPR activation are critical in maintaining ER proteostasis, with prolonged stress leading to cell death.

Conclusions:

• Understanding ER processing of immune checkpoint proteins is crucial for their functional integrity.
• ER quality control and degradation pathways play a vital role in regulating immune checkpoint protein levels and function.
• Targeting ER pathways presents potential avenues for novel immunotherapies.