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Updated: Jul 17, 2026

In Vitro Analysis of E3 Ubiquitin Ligase Function
06:06

In Vitro Analysis of E3 Ubiquitin Ligase Function

Published on: May 14, 2021

Ligand-induced ubiquitination unleashes LAG3 immune checkpoint function by hindering membrane sequestration of

Yong Jiang1, Anran Dai2, Yuwei Huang3

  • 1School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China; Key Laboratory of Multi-Cell Systems, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai 200031, China.

Cell
|March 18, 2025
PubMed

Insights

Lymphocyte activation gene 3 (LAG3) is activated by non-K48-linked polyubiquitination upon ligand binding, enhancing its immune suppression. This mechanism, targeted by therapeutic antibodies, offers new cancer immunotherapy strategies.

Area of Science:

  • Immunology
  • Molecular Biology
  • Cancer Research

Background:

  • Lymphocyte activation gene 3 (LAG3) is a key immune checkpoint target in cancer immunotherapy.
  • The precise mechanism of LAG3 activation following ligand engagement has remained unclear.

Purpose of the Study:

  • To elucidate the molecular mechanism of LAG3 activation upon ligand binding.
  • To investigate the role of ubiquitination in LAG3 function and its implications for cancer immunotherapy.

Main Methods:

  • Studied LAG3 ubiquitination using biochemical assays and cell-based models.
  • Investigated the role of E3 ligases c-Cbl and Cbl-b in LAG3 ubiquitination.
  • Analyzed the impact of LAG3 ubiquitination on antitumor immunity in vivo.
  • Correlated therapeutic antibody effects with LAG3 ubiquitination levels.

Main Results:

  • Ligand engagement triggers non-K48-linked polyubiquitination of LAG3, enhancing its inhibitory function.
  • Major histocompatibility complex class II (MHC class II) and membrane-bound fibrinogen-like protein 1 (FGL1) induce LAG3 ubiquitination.
  • Ubiquitination, mediated by c-Cbl and Cbl-b, stabilizes the LAG3 cytoplasmic tail, promoting signaling.
  • LAG3 ubiquitination is essential for suppressing antitumor immunity in vivo.
  • Therapeutic LAG3 antibodies inhibit LAG3 ubiquitination, correlating with checkpoint blockade efficacy.

Conclusions:

  • LAG3 activation involves non-K48-linked polyubiquitination, promoting its immune suppressive function.
  • This ubiquitination mechanism is critical for LAG3-mediated T-cell suppression and represents a target for cancer immunotherapy.
  • LAG3/CBL coexpression may serve as a predictive biomarker for response to LAG3 blockade therapies.
Keywords:
Cbl-bLAG3TCR signalingc-Cblcancer immunotherapycheckpointubiquitination

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