Transforming growth factor beta

Computer graphic of TGF-beta. TGF-beta is a cytokine with three different isoforms, which regulates many cellular functions including cell proliferation, differentiation, adhesion and migration

Transforming growth factor beta (TGF-β) is a multifunctional cytokine belonging to the transforming growth factor superfamily that includes three[1] different mammalian isoforms (TGF-β 1 to 3, HGNC symbols TGFB1, TGFB2, TGFB3) and many other signaling proteins. TGFB proteins are produced by all white blood cell lineages.

Activated TGF-β complexes with other factors to form a serine/threonine kinase complex that binds to TGF-β receptors. TGF-β receptors are composed of both type 1 and type 2 receptor subunits. After the binding of TGF-β, the type 2 receptor kinase phosphorylates and activates the type 1 receptor kinase that activates a signaling cascade.[2] This leads to the activation of different downstream substrates and regulatory proteins, inducing transcription of different target genes that function in differentiation, chemotaxis, proliferation, and activation of many immune cells.[2][3]

TGF-β is secreted by many cell types, including macrophages, in a latent form in which it is complexed with two other polypeptides, latent TGF-beta binding protein (LTBP) and latency-associated peptide (LAP). Serum proteinases such as plasmin catalyze the release of active TGF-β from the complex. This often occurs on the surface of macrophages where the latent TGF-β complex is bound to CD36 via its ligand, thrombospondin-1 (TSP-1). Inflammatory stimuli that activate macrophages enhance the release of active TGF-β by promoting the activation of plasmin. Macrophages can also endocytose IgG-bound latent TGF-β complexes that are secreted by plasma cells and then release active TGF-β into the extracellular fluid.[4] Among its key functions is regulation of inflammatory processes, particularly in the gut.[5] TGF-β also plays a crucial role in stem cell differentiation as well as T-cell regulation and differentiation.[6][7]

Because of its role in immune and stem cell regulation and differentiation, it is a highly researched cytokine in the fields of cancer, auto-immune diseases, and infectious disease.

The TGF-β superfamily includes endogenous growth inhibiting proteins; an increase in expression of TGF-β often correlates with the malignancy of many cancers and a defect in the cellular growth inhibition response to TGF-β. Its immunosuppressive functions then come to dominate, contributing to oncogenesis.[8] The dysregulation of its immunosuppressive functions is also implicated in the pathogenesis of autoimmune diseases, although their effect is mediated by the environment of other cytokines present.[5][9]

  1. ^ Meng, Xiao-ming; Nikolic-Paterson, David J.; Lan, Hui Yao (June 2016). "TGF-β: the master regulator of fibrosis". Nature Reviews Nephrology. 12 (6): 325–338. doi:10.1038/nrneph.2016.48. PMID 27108839. S2CID 25871413.
  2. ^ a b Massagué J (October 2012). "TGFβ signalling in context". Nature Reviews. Molecular Cell Biology. 13 (10): 616–30. doi:10.1038/nrm3434. PMC 4027049. PMID 22992590.
  3. ^ Nakao A, Afrakhte M, Morén A, Nakayama T, Christian JL, Heuchel R, et al. (October 1997). "Identification of Smad7, a TGFbeta-inducible antagonist of TGF-beta signalling". Nature. 389 (6651): 631–5. Bibcode:1997Natur.389..631N. doi:10.1038/39369. PMID 9335507. S2CID 4311145.
  4. ^ AfCS signaling gateway – data center – ligand description
  5. ^ a b Letterio JJ, Roberts AB (April 1998). "Regulation of immune responses by TGF-beta". Annual Review of Immunology. 16 (1): 137–61. doi:10.1146/annurev.immunol.16.1.137. PMID 9597127.
  6. ^ Massagué J, Xi Q (July 2012). "TGF-β control of stem cell differentiation genes". FEBS Letters. 586 (14): 1953–8. doi:10.1016/j.febslet.2012.03.023. PMC 3466472. PMID 22710171.
  7. ^ Li MO, Flavell RA (August 2008). "TGF-beta: a master of all T cell trades". Cell. 134 (3): 392–404. doi:10.1016/j.cell.2008.07.025. PMC 3677783. PMID 18692464.
  8. ^ Massagué J, Blain SW, Lo RS (October 2000). "TGFbeta signaling in growth control, cancer, and heritable disorders". Cell. 103 (2): 295–309. doi:10.1016/S0092-8674(00)00121-5. PMID 11057902. S2CID 15482063.
  9. ^ Lichtman, Michael K.; Otero-Vinas, Marta; Falanga, Vincent (March 2016). "Transforming growth factor beta (TGF-β) isoforms in wound healing and fibrosis". Wound Repair and Regeneration. 24 (2): 215–222. doi:10.1111/wrr.12398. ISSN 1524-475X. PMID 26704519. S2CID 4967954.