protein · BEGINNER LESSON
FGL2
FGL2, or fibrinogen-like protein 2, is a protein made in several cell types that has two main forms: a membrane-bound form and a secreted soluble form. It is involved in coagulation and immune regulation, and studies link it to tumor behavior in several cancers.
What FGL2 is
FGL2 stands for fibrinogen-like protein 2. It is a human protein encoded on chromosome 7q11.23 and belongs to the fibrinogen-like protein family. The sources describe two structural forms in humans: membrane-associated FGL2 (mFGL2) and secreted soluble FGL2 (sFGL2). FGL2 is reported in macrophages, endothelial cells, T cells, tumor cells, and other cell types, and it has roles in coagulation and immunoregulation.
[1] Preliminary exploration of the role of fibrinogen-like protein 2 in neuroblastoma [3] Disruption of FGL2 induces TFEB-dependent lysosomal ... - PMC
How the two forms differ
mFGL2 is a type II transmembrane protein, meaning it sits in the cell membrane with part of the protein exposed outside the cell. It has both N-terminal and C-terminal regions and can act as an immune coagulator by cleaving prothrombin, a blood-clotting precursor. sFGL2 lacks the membrane region, is secreted into plasma, and is described as an inflammatory and immunosuppressive mediator that can affect T cell proliferation and the activity of regulatory T cells, which are T cells that help restrain immune responses.
[1] Preliminary exploration of the role of fibrinogen-like protein 2 in neuroblastoma
What FGL2 does in cancer studies
The sources link FGL2 to tumor biology in several cancers. In neuroblastoma, lower FGL2 expression was seen in higher-risk samples, and experiments suggested FGL2 slows proliferation, migration, and invasion of neuroblastoma cells. In hepatocellular carcinoma, FGL2 was reported to promote immune escape by increasing PD-L1 and supporting tumor progression. In other tumor models, loss of FGL2 reduced tumor growth and changed immune behavior.
[1] Preliminary exploration of the role of fibrinogen-like protein 2 in neuroblastoma [3] Disruption of FGL2 induces TFEB-dependent lysosomal ... - PMC [2] Fgl2-knockout tumor cells serve as a vaccine inducing long ...
Mechanisms reported in the sources
In neuroblastoma, FGL2 was tied to reduced NF-kappa B signaling. NF-kappa B is a transcription factor, a protein that helps turn genes on or off. When FGL2 was reduced, phosphorylation changes increased NF-kappa B activity and promoted epithelial-mesenchymal transition, or EMT, a cell-state change that can help cells move and invade. In hepatocellular carcinoma, FGL2 activated mTORC1, a signaling complex, which kept TFEB from entering the nucleus. TFEB is a transcription factor that supports lysosome biogenesis, the making of lysosomes, so this reduced lysosomal degradation of PD-L1. In another tumor study, FGL2 knockout lowered CD47 through Src and PKCα pathways; CD47 is a cell-surface signal often called a “don’t eat me” cue.
[1] Preliminary exploration of the role of fibrinogen-like protein 2 in neuroblastoma [2] Fgl2-knockout tumor cells serve as a vaccine inducing long ... [3] Disruption of FGL2 induces TFEB-dependent lysosomal ... - PMC
Limits of the evidence
The evidence in these sources comes from cell studies, mouse models, and tumor samples, so it does not prove the same effects will occur in every human cancer or patient. One neuroblastoma study also notes a relatively small sample size and that it did not separate the contributions of mFGL2 and sFGL2. Some findings are pathway-based and need further validation.
[1] Preliminary exploration of the role of fibrinogen-like protein 2 in neuroblastoma [2] Fgl2-knockout tumor cells serve as a vaccine inducing long ... [3] Disruption of FGL2 induces TFEB-dependent lysosomal ... - PMC
SEE THE IDEA
FGL2 in cells and tumors
Membrane form (mFGL2) and secreted form (sFGL2) have different locations and roles.
mFGL2 can cleave prothrombin; sFGL2 can shape inflammation and T cell behavior.
FGL2 can alter NF-kappa B, EMT, mTORC1, TFEB, PD-L1, and CD47 pathways.
Depending on the cancer model, FGL2 may restrain or promote tumor progression.
FGL2 has form-specific actions that connect cell signaling to immune and tumor behavior.
Simple pathway view: structure influences signaling, and signaling influences cancer-related outcomes.
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Sources and further reading
This general lesson was generated from public source material. It explains a concept; it does not interpret a private paper or provide medical advice.