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LAG3

Domain

Lymphocyte activation gene 3 protein

The KIEELE motif is essential for TCR inhibition (PubMed:37788323). Its ubiquitination by CBL and CBLB unleashes the RRFSALE motif from the membrane, initiating a signaling that prevents TCR activation (PubMed:40101708).

Lymphocyte activation gene 3 protein

The RRFSALE motif is essential for TCR inhibition (PubMed:37788323, PubMed:40592325). In absence of ligand, the RRFSALE motif associates with the membrane; ligand-binding and subsequent ubiquitination unleashes the motif, initiating a signaling that prevents TCR activation (PubMed:40101708).

Function

Lymphocyte activation gene 3 protein

Inhibitory receptor on antigen activated T-cells (PubMed:20421648, PubMed:35761082, PubMed:7805750, PubMed:8647185). Delivers inhibitory signals upon binding to ligands, such as MHC class II, its main ligand present at the surface of antigen-presenting cells (APCs), and FGL1, which is secreted by hepatocytes and certain types of tumor cells (PubMed:30580966, PubMed:32920841, PubMed:35761082, PubMed:39671469, PubMed:7589152, PubMed:8647185, PubMed:9159144). Ligand-binding initiates a signaling that inhibits the T-cell receptor (TCR) in the immunological synapse, preventing T-cell activation (PubMed:40101708). Mechanistically, ligand-binding promotes (1) ubiquitination of the KIEELE motif, unleashing the RRFSALE motif from the membrane and (2) leading to the formation of condensates with the TCR component CD3E, thereby disrupting the association between CD3E and LCK and preventing TCR activation (PubMed:40101708, PubMed:40592325). May inhibit antigen-specific T-cell activation in synergy with PDCD1/PD-1 (By similarity). Negatively regulates the proliferation, activation, effector function and homeostasis of both CD8(+) and CD4(+) T-cells (PubMed:20421648, PubMed:7805750, PubMed:8647185). Also mediates immune tolerance: constitutively expressed on a subset of regulatory T-cells (Tregs) and contributes to their suppressive function (By similarity). Also acts as a negative regulator of plasmacytoid dendritic cell (pDCs) activation (By similarity).

The LAG3-mediated inhibitory pathway is exploited by tumors to attenuate anti-tumor immunity and escape destruction by the immune system, thereby facilitating tumor survival (PubMed:35981087, PubMed:40101708). The blockage of the LAG3- and PDCD1-mediated pathways results in the reversal of the exhausted T-cell phenotype and the normalization of the anti-tumor response, providing a rationale for cancer immunotherapy (PubMed:35981087, PubMed:40101708).

Secreted lymphocyte activation gene 3 protein

May function as a ligand for MHC class II (MHC-II) on antigen-presenting cells (APC), promoting APC activation/maturation and driving Th1 immune response.

Post-translational modifications

Lymphocyte activation gene 3 protein

Ubiquitinated by CBL and CBLB in response to ligand-binding, initiating a signaling that prevents TCR activation: ubiquitination at Lys-498 via 'Lys-63'-linked ubiquitin chains unleashes the RRFSALE motif from the membrane (PubMed:40101708). MHC class II and membrane-bound FGL1 promote ubiquitination by CBL and CBLB; in contrast secreted FGL1 is not able to trigger LAG3 ubiquitination (PubMed:40101708).

Lymphocyte activation gene 3 protein

Proteolytically cleaved by ADAM10 and ADAM17 within the connecting peptide region, leading to release of Secreted lymphocyte activation gene 3 protein (sLAG-3). ADAM10 mediates constitutive cleavage, but cleavage increases following T-cell activation, whereas shedding by ADAM17 is induced by TCR signaling in a PRKCQ-dependent manner.

Sequence Similarities

Belongs to the LAG3 family.

Tissue Specificity

Primarily expressed in activated T-cells and a subset of natural killer (NK) cells.

Cellular localization

Alternative names

CD223, FDC, LAG3, Lymphocyte activation gene 3 protein, LAG-3

swissprot:P18627 omim:153337 entrezGene:3902

Other research areas