Transforming growth factor beta
Transforming growth factor beta (TGF-β) is a secreted protein that controls proliferation, cellular differentiation, and other functions in most cells. It is a type of cytokine which plays a role in immunity, cancer, bronchial asthma, lung fibrosis, heart disease, diabetes, Hereditary hemorrhagic telangiectasia, Marfan syndrome, Vascular Ehlers-Danlos syndrome, Loeys–Dietz syndrome, Parkinson's disease, Chronic kidney disease, Multiple Sclerosis and AIDS.
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.
TGF-β exists in at least three isoforms called TGF-β1, TGF-β2 and TGF-β3. Until the three isoforms were discovered, TGF-β referred to TGF-β1, as it was the first member of this family to be discovered. The TGF-β family is part of a superfamily of proteins known as the transforming growth factor beta superfamily, which includes inhibins, activin, anti-müllerian hormone, bone morphogenetic protein, decapentaplegic and Vg-1.
Most tissues have high expression of the genes encoding TGF-β. In contrast, other anti-inflammatory cytokines such as IL-10, whose expression is minimal in unstimulated tissues and seems to require triggering by commensal or pathogenic flora.
TGF-β acts as an antiproliferative factor in normal epithelial cells and at early stages of oncogenesis. Some cells that secrete TGF-β also have receptors for TGF-β. This is known as autocrine signalling. Cancerous cells increase their production of TGF-β, which also acts on surrounding cells.
- 1 Structure
- 2 Function
- 3 Clinical significance
- 4 Types
- 5 Activation
- 6 Latency (latent TGF-β complex)
- 7 Integrin-independent activation
- 8 Activation by Alpha(V) containing integrins
- 9 See also
- 10 External links
- 11 References
The peptide structures of the TGF-β isoforms are highly similar (homologies on the order of 70-80 %). They are all encoded as large protein precursors; TGF-β1 contains 390 amino acids and TGF-β2 and TGF-β3 each contain 412 amino acids. They each have an N-terminal signal peptide of 20-30 amino acids that they require for secretion from a cell, a pro-region (called latency associated peptide or LAP), and a 112-114 amino acid C-terminal region that becomes the mature TGF-β molecule following its release from the pro-region by proteolytic cleavage. The mature TGF-β protein dimerizes to produce a 25 KDa active protein with many conserved structural motifs. TGF-β has nine cysteine residues that are conserved among its family. Eight form disulfide bonds within the protein to create a cysteine knot structure characteristic of the TGF-β superfamily. While, the ninth cysteine forms a disulfide bond with the ninth cysteine of another TGF-β protein to produce a dimer. Many other conserved residues in TGF-β are thought to form secondary structure through hydrophobic interactions. The region between the fifth and sixth conserved cysteines houses the most divergent area of TGF-β proteins that is exposed at the surface of the protein and is implicated in receptor binding and specificity of TGF-β.
The SMAD pathway is the canonical signaling pathway that TGF-β family members signal through. In this pathway, TGF-β dimers bind to a type II receptor which recruits and phosphorylates a type I receptor. The type I receptor then recruits and phosphorylates a receptor regulated SMAD (R-SMAD). The R-SMAD then binds to the common SMAD (coSMAD) SMAD4 and forms a heterodimeric complex. This complex then enters the cell nucleus where it acts as a transcription factor for various genes, including those to activate the mitogen-activated protein kinase 8 pathway, which triggers apoptosis. The SMAD pathway is regulated by feedback inhibition. SMAD6 and SMAD7 may block type-I receptors.
There is evidence of association and binding between DAXX (DAXX adapter protein) and type II TGF-β receptor kinase.
TGF-β causes synthesis of p15 and p21 proteins, which block the cyclin:CDK complex responsible for Retinoblastoma protein (Rb) phosphorylation. Thus TGF-β blocks advance through the G1 phase of the cycle. In doing so, TGF-β suppresses expression of c-myc, a gene which is involved in G1 cell cycle progression.
TGF-β is believed to be important in regulation of the immune system by Foxp3+ Regulatory T cell and the differentiation of both Foxp3+ Regulatory T cell and of Th17 cells from CD4+ T cells. TGF-β appears to block the activation of lymphocytes and monocyte derived phagocytes.
TGF-β can serve as a graded morphogen, causing cell differentiation in a developing cell.
In normal cells, TGF-β, acting through its signaling pathway, stops the cell cycle at the G1 stage to stop proliferation, induce differentiation, or promote apoptosis. When a cell is transformed into a cancer cell, parts of the TGF-β signaling pathway are mutated, and TGF-β no longer controls the cell. These cancer cells proliferate. The surrounding stromal cells (fibroblasts) also proliferate. Both cells increase their production of TGF-β. This TGF-β acts on the surrounding stromal cells, immune cells, endothelial and smooth-muscle cells. It causes immunosuppression and angiogenesis, which makes the cancer more invasive. TGF-β also converts effector T-cells, which normally attack cancer with an inflammatory (immune) reaction, into regulatory (suppressor) T-cells, which turn off the inflammatory reaction.
One animal study suggests that cholesterol suppresses the responsiveness of cardiovascular cells to TGF-β and its protective qualities, thus allowing atherosclerosis and heart disease to develop, while statins, drugs that lower cholesterol levels, may enhance the responsiveness of cardiovascular cells to the protective actions of TGF-β.
TGF-β is involved in regeneration of zebrafish heart.
TGF-β signaling also likely plays a major role in the pathogenesis of Marfan syndrome, a disease characterized by disproportionate height, arachnodactyly, ectopia lentis and heart complications such as mitral valve prolapse and aortic enlargement increasing the likelihood of aortic dissection. While the underlying defect in Marfan syndrome is faulty synthesis of the glycoprotein fibrillin I, normally an important component of elastic fibers, it has been shown that the Marfan syndrome phenotype can be relieved by addition of a TGF-β antagonist in affected mice. This suggests that while the symptoms of Marfan syndrome may seem consistent with a connective tissue disorder, the mechanism is more likely related to reduced sequestration of TGF-β by fibrillin.
TGF-β signaling is also disturbed in Loeys–Dietz syndrome which is caused by mutations in the TGFB receptor.
TGF-β/SMAD3 signaling pathway is important in regulating glucose and energy homeostasis and might play a role in diabetic nephropathy.
Chronic kidney disease
In chronic kidney disease, TGF-β blocks fatty acid metabolism in human tubular epithelial cells, and those cells don't switch to glucose metabolism in response. That deprives them of energy, leads to the accumulation of fatty deposits, and causes fibrosis in the kidneys. Blocking TGF-β prevents damage to tubular epithelial cells and reduces fibrosis.
Induced T regulatory cells (iTreg), stimulated by TGF-β in the presence of IL-2, suppressed the development of Experimental Autoimmune Encephalomyelitis (EAE), an animal model of Multiple Sclerosis(MS) via a Foxp3 and IL-10 mediated response. This suggests a possible role for TGF-β and iTreg in the regulation and treatment of MS.
Decreased levels of TGF-β have been observed in patients diagnosed with Multiple Sclerosis. It's role in Multiple Sclerosis can be explained due to TGF-β role in regulating apoptosis of Th17 cells. When TGF-β levels decrease, they are unable to induce Th17 cells apoptosis. Th17 cells secretes TNFα, which induces demylenation of the oliodendroglial via TNF receptor 1. The decreased TGF-β levels lead to increased Th17 cells and subsequently increased TNFα levels. As a result, demylenation of neurons occurs. TGF-β have also been observed to induce Oligodendrocyte (myelin sheath producing cells) growth. Hence, the decreased TGF-β levels during MS also prevent remylenation of neurons.
Higher concentrations of TGF-β are found in the blood and cerebrospinal fluid of patients with Alzheimer's Disease as compared to control subjects, suggesting a possible role in the neurodegenerative cascade leading to Alzheimer's Disease symptoms and pathology.
The primary three are:
- TGFβ4 precursor was discovered as a gene upregulated during pre-menstrual phase in the endometrial stroma (Kothapalli et al. 1997) and called EBAF (endometrial bleeding associated factor). Later independently discovered to be involved in vertebrate embryonic left right asymmetry determination, and given the name lefty2 (also called Lefty A).
Although TGF-β is important in regulating crucial cellular activities, only a few TGF-β activating pathways are currently known, and the full mechanism behind the suggested activation pathways is not yet well understood. Some of the known activating pathways are cell or tissue specific, while some are seen in multiple cell types and tissues. Proteases, integrins, pH, and reactive oxygen species are just few of the currently know factors that can activate TGF-β. It is well known that perturbations of these activating factors can lead to unregulated TGF-β signaling levels that may cause several complications including inflammation, autoimmune disorders, fibrosis, cancer and cataracts. In most cases an activated TGF-β ligand will initiate the TGF-β signaling cascade as long as TGF-β receptors I and II are within reach, this is due to high affinity between TGF-β and its receptors, suggesting why the TGF-β signaling recruits a latency system to mediate its signaling.
Latency (latent TGF-β complex)
All three TGF-βs are synthesized as precursor molecules containing a propeptide region in addition to the TGF-β homodimer. After it is synthesized, the TGF-β homodimer interacts with a Latency Associated Peptide (LAP)[a protein derived from the N-terminal region of the TGF beta gene product] forming a complex called Small Latent Complex (SLC). This complex remains in the cell until it is bound by another protein called Latent TGF-β-Binding Protein (LTBP), forming a larger complex called Large Latent Complex (LLC). It is LLC that get secreted to the extracellular matrix (ECM).
In most cases, before the LLC is secreted, the TGF-β precursor is cleaved from the propeptide but remains attached to it by noncovalent bonds. After its secretion, it remains in the extracellular matrix as an inactivated complex containing both the LTBP and the LAP which need to be further processed in order to release active TGF-β. The attachment of TGF-β to the LTBP is by disulfide bond which allows it to remain inactive by preventing it from binding to its receptors. Because different cellular mechanisms require distinct levels of TGF-β signaling, the inactive complex of this cytokine gives opportunity for a proper mediation of TGF-β signaling.
There are four different LTBP isoforms known, LTBP-1, LTBP-2, LTBP-3 and LTBP-4. Mutation or alteration of LAP or LTBP can result to improper TGF-β signaling. Mice lacking LTBP-3 or LTBP-4 demonstrate phenotypes consistent to phenotypes seen in mice with altered TGF-β signaling. Furthermore, specific LTBP isoforms have a propensity to associate with specific LAP•TGF-β isoforms. For example, LTBP-4 is reported to bind only to TGF-β1, thus, mutation in LTBP-4 can lead to TGF-β associated complications which are specific to tissues that predominantly involves TGF-β1. Moreover, the structural differences within the LAP’s provide different latent TGF-β complexes which are selective but to specific stimuli generated by specific activators.
- Activation by protease and metalloprotease
Plasmin and a number of matrix metalloproteinases (MMP) play a key role in promoting tumor invasion and tissue remodeling by inducing proteolysis of several ECM components. The TGF-β activation process involves the release of the LLC from the matrix, followed by further proteolysis of the LAP to release TGF-β to its receptors. MMP-9 and MMP-2 are known to cleave latent TGF-β. The LAP complex contains a protease-sensitive hinge region which can be the potential target for this liberation of TGF-β. Despite the fact that MMPs have been proven to play a key role in activating TGF-β, mice with mutations in MMP-9 and MMP-2 genes can still activate TGF-β and do not show any TGF-β deficiency phenotypes, this may reflect redundancy among the activating enzymes suggesting that other unknown proteases might be involved.
- Activation by pH
Acidic conditions can denature the LAP. Treatment of the medium with extremes of pH (1.5 or 12) resulted in significant activation of TGF beta as shown by radio-receptor assays, while mild acid treatment (pH 4.5) yielded only 20-30% of the competition achieved by pH 1.5.
- Activation reactive oxygen species (ROS)
The LAP structure is important to maintain its function. Structure modification of the LAP can lead to disturbing the interaction between LAP and TGF-β and thus activating it. Factors that may cause such modification may include hydroxyl radicals from reactive oxygen species (ROS). TGF-β was rapidly activated after in vivo radiation exposure ROS.
- Activation by thrombospondin-1
Thrombospondin-1 (TSP-1) is a matricellular glycoprotein found in plasma of healthy patients with levels in the range of 50–250 ng/ml. TSP-1 levels are known to increase in response to injury and during development. TSP-1 activates latent TGF-beta by forming direct interactions with the latent TGF-β complex and induces a conformational rearrangement preventing it from binding to the matured TGF-β.
Activation by Alpha(V) containing integrins
The general theme of integrins to participate in latent TGF-β1 activation, arose from studies that examined mutations/knockouts of β6 integrin, αV integrin, β8 integrin and in LAP. These mutations produced phenotypes that were similar to phenotypes seen in TGF-β1 knockout mice. Currently there are two proposed models of how αV containing integrins can activate latent TGF-β1; the first proposed model is by inducing conformational change to the latent TGF-β1 complex and hence releasing the active TGF-β1 and the second model is by a protease-dependent mechanism.
- Conformation change mechanism pathway (without proteolysis)
αVβ6 integrin was the first integrin to be identified as TGF-β1 activator. LAPs contain an RGD motif which is recognized by vast majority of αV containing integrins, and αVβ6 integrin can activate TGF-β1 by binding to the RGD motif present in LAP-β1 and LAP-β 3. Upon binding, it induces adhesion-mediated cell forces that are translated into biochemical signals which can lead to liberation/activation of TGFb from its latent complex. This pathway has been demonstrated for activation of TGF-β in epithelial cells and does not associate MMPs.
- Integrin protease-dependent activation mechanism
Because MMP-2 and MMP-9 can activate TGF-β through proteolytic degradation of the latent TGF beta complex, αV containing integrins activate TGF-β1 by creating a close connection between the latent TGF-β complex and MMPs. Integrins αVβ6 and αVβ3 are suggested to simultaneously bind the latent TGF-β1 complex and proteinases, simultaneous inducing conformation changes of the LAP and sequestering proteases to close proximity. Regardless of involving MMPs, this mechanism still necessitate the association of intergrins and that makes it a non protolylic pathway.
- Anita Roberts, a molecular biologist who made pioneering observations of TGF-β
- Description of the TGF beta producing genes at ncbi.nlm.nih.gov
- Diagram of the TGF beta signaling pathway at genome.ad.jp
- The TGF-beta system — Nature Reviews Molecular Cell Biology
- SMART:TGFB domain annotation — European Molecular Biology Laboratory Heidelberg
- TGF-beta at the US National Library of Medicine Medical Subject Headings (MeSH)
- Biochemists Solve Structure Of TGF-Beta And Its Receptor. 2008 Shows TGF-β3 dimer in TGFB-receptor.
- Measurement of Human Latent TGF-β1
- TGF beta pathway diagram
- AfCS signaling gateway - data center - ligand description
- Li X, Mai J, Virtue A et al. (March 2012). "IL-35 is a novel responsive anti-inflammatory cytokine--a new system of categorizing anti-inflammatory cytokines". PLoS ONE 7 (3): e33628. doi:10.1371/journal.pone.0033628. PMID 22438968.
- Jennifer J Hill, Tammy-Lynn Tremblay, Christiane Cantin, Maureen O'Connor-McCourt, John F Kelly and Anne EG Lenferink (2009-01-08). "Glycoproteomic analysis of two mouse mammary cell lines during transforming growth factor (TGF)-beta induced epithelial to mesenchymal transition". 7thspace.com. Retrieved 2009-01-21.
- Khalil N (1999). "TGF-beta: from latent to active". Microbes Infect 1 (15): 1255–63. doi:10.1016/S1286-4579(99)00259-2. PMID 10611753.
- Herpin A, Lelong C, Favrel P (2004). "Transforming growth factor-beta-related proteins: an ancestral and widespread superfamily of cytokines in metazoans". Dev Comp Immunol 28 (5): 461–85. doi:10.1016/j.dci.2003.09.007. PMID 15062644.
- Daopin S, Piez K, Ogawa Y, Davies D (1992). "Crystal structure of transforming growth factor-beta 2: an unusual fold for the superfamily". Science 257 (5068): 369–73. doi:10.1126/science.1631557. PMID 1631557.
- Hanahan D, Weinberg RA (January 2000). "The hallmarks of cancer". Cell 100 (1): 57–70. doi:10.1016/S0092-8674(00)81683-9. PMID 10647931.
- Blobe GC, Schiemann WP, Lodish HF (May 2000). "Role of transforming growth factor beta in human disease". N. Engl. J. Med. 342 (18): 1350–8. doi:10.1056/NEJM200005043421807. PMID 10793168.
- Understanding Heart Disease: Research Explains Link Between Cholesterol and Heart Disease
- Entrez Gene (2007). "TGFBR2 transforming growth factor, beta receptor II" (ENTREZ GENE ENTRY). Retrieved January 11, 2007.
- Habashi JP, Judge DP, Holm TM et al. (April 2006). "Losartan, an AT1 antagonist, prevents aortic aneurysm in a mouse model of Marfan syndrome". Science 312 (5770): 117–21. doi:10.1126/science.1124287. PMC 1482474. PMID 16601194.
- Robinson PN, Arteaga-Solis E, Baldock C et al. (October 2006). "The molecular genetics of Marfan syndrome and related disorders". J. Med. Genet. 43 (10): 769–87. doi:10.1136/jmg.2005.039669. PMC 2563177. PMID 16571647.
- Selvaraj RK, Geiger T (March 2008). "Mitigation of experimental allergic encephalomyelitis by TGF-beta induced Foxp3+ regulatory T lymphocytes through the induction of anergy and infectious tolerance". Journal of immunology 180 (5): 2830–2838. doi:10.4049/jimmunol.180.5.2830. PMID 18292504.
- Dobolyi A, Vincze C, Pál G, Lovas G (July 2012). "The neuroprotective functions of transforming growth factor Beta proteins". Int J Mol Sci. 13 (7): 8219–58. doi:10.3390/ijms13078219. PMC 3430231. PMID 22942700.
- Nakahara J, Maeda M, Aiso S, Suzuki N (February 2012). "Current concepts in multiple sclerosis: autoimmunity versus oligodendrogliopathy.". Clinical reviews in allergy & immunology 42 (1): 26–34. doi:10.1007/s12016-011-8287-6. PMID 22189514.
- Swardfager W, Lanctôt K, Rothenburg L, Wong A, Cappell J, Herrmann N (November 2010). "A meta-analysis of cytokines in Alzheimer's disease". Biol. Psychiatry 68 (10): 930–41. doi:10.1016/j.biopsych.2010.06.012. PMID 20692646.
- Maier P, Broszinski A, Heizmann U, Böhringer D, Reinhardau T (2007). "Active transforming growth factor-beta2 is increased in the aqueous humor of keratoconus patients". Molecular Vision 13: 1198–202. PMID 17679942.
- Engler C, Chakravarti S, Doyle J, Eberhart CG, Meng H, Stark WJ, Kelliher C, Jun AS (May 2011). "Transforming growth factor-β signaling pathway activation in Keratoconus". American Journal of Ophthalmology 151 (5): 752–759.e2. doi:10.1016/j.ajo.2010.11.008. PMC 3079764. PMID 21310385.
- Kothapalli R, Buyuksal I, Wu SQ, Chegini N, Tabibzadeh S (May 1997). "Detection of ebaf, a novel human gene of the transforming growth factor beta superfamily association of gene expression with endometrial bleeding". J. Clin. Invest. 99 (10): 2342–50. doi:10.1172/JCI119415. PMC 508072. PMID 9153275.
- Annes JP, Munger JS, Rifkin DB (January 2003). "Making sense of latent TGFbeta activation". J. Cell. Sci. 116 (Pt 2): 217–24. doi:10.1242/jcs.00229. PMID 12482908.
- ten Dijke P, Hill CS (May 2004). "New insights into TGF-beta-Smad signalling". Trends Biochem. Sci. 29 (5): 265–73. doi:10.1016/j.tibs.2004.03.008. PMID 15130563.
- Stetler-Stevenson WG, Aznavoorian S, Liotta LA (1993). "Tumor cell interactions with the extracellular matrix during invasion and metastasis". Annu. Rev. Cell Biol. 9: 541–73. doi:10.1146/annurev.cb.09.110193.002545. PMID 8280471.
- Barcellos-Hoff MH, Dix TA (September 1996). "Redox-mediated activation of latent transforming growth factor-beta 1". Mol. Endocrinol. 10 (9): 1077–83. doi:10.1210/me.10.9.1077. PMID 8885242.
- Wipff PJ, Hinz B (September 2008). "Integrins and the activation of latent transforming growth factor beta1 — an intimate relationship". Eur. J. Cell Biol. 87 (8-9): 601–15. doi:10.1016/j.ejcb.2008.01.012. PMID 18342983.
- Yu Q, Stamenkovic I (January 2000). "Cell surface-localized matrix metalloproteinase-9 proteolytically activates TGF-beta and promotes tumor invasion and angiogenesis". Genes Dev. 14 (2): 163–76. PMC 316345. PMID 10652271.
- Taipale J, Miyazono K, Heldin CH, Keski-Oja J (January 1994). "Latent transforming growth factor-beta 1 associates to fibroblast extracellular matrix via latent TGF-beta binding protein". J. Cell Biol. 124 (1-2): 171–81. doi:10.1083/jcb.124.1.171. PMC 2119892. PMID 8294500.
- Derynck R, Jarrett JA, Chen EY et al. (1985). "Human transforming growth factor-beta complementary DNA sequence and expression in normal and transformed cells". Nature 316 (6030): 701–5. doi:10.1038/316701a0. PMID 3861940.
- Rifkin DB (March 2005). "Latent transforming growth factor-beta (TGF-beta) binding proteins: orchestrators of TGF-beta availability". J. Biol. Chem. 280 (9): 7409–12. doi:10.1074/jbc.R400029200. PMID 15611103.
- Dubois CM, Laprise MH, Blanchette F, Gentry LE, Leduc R (May 1995). "Processing of transforming growth factor beta 1 precursor by human furin convertase". J. Biol. Chem. 270 (18): 10618–24. doi:10.1074/jbc.270.18.10618. PMID 7737999.
- Saharinen J, Hyytiäinen M, Taipale J, Keski-Oja J (June 1999). "Latent transforming growth factor-beta binding proteins (LTBPs)--structural extracellular matrix proteins for targeting TGF-beta action". Cytokine Growth Factor Rev. 10 (2): 99–117. doi:10.1016/S1359-6101(99)00010-6. PMID 10743502.
- Sterner-Kock A, Thorey IS, Koli K et al. (September 2002). "Disruption of the gene encoding the latent transforming growth factor-beta binding protein 4 (LTBP-4) causes abnormal lung development, cardiomyopathy, and colorectal cancer". Genes Dev. 16 (17): 2264–73. doi:10.1101/gad.229102. PMC 186672. PMID 12208849.
- Saharinen J, Keski-Oja J (August 2000). "Specific sequence motif of 8-Cys repeats of TGF-beta binding proteins, LTBPs, creates a hydrophobic interaction surface for binding of small latent TGF-beta". Mol. Biol. Cell 11 (8): 2691–704. doi:10.1091/mbc.11.8.2691. PMC 14949. PMID 10930463.
- Lyons RM, Keski-Oja J, Moses HL (May 1988). "Proteolytic activation of latent transforming growth factor-beta from fibroblast-conditioned medium". J. Cell Biol. 106 (5): 1659–65. doi:10.1083/jcb.106.5.1659. PMC 2115066. PMID 2967299.
- Booth WJ, Berndt MC (July 1987). "Thrombospondin in clinical disease states". Semin. Thromb. Hemost. 13 (3): 298–306. doi:10.1055/s-2007-1003505. PMID 3317840.
- Raugi GJ, Olerud JE, Gown AM (December 1987). "Thrombospondin in early human wound tissue". J. Invest. Dermatol. 89 (6): 551–4. doi:10.1111/1523-1747.ep12461198. PMID 3680981.
- Schultz-Cherry S, Murphy-Ullrich JE (August 1993). "Thrombospondin causes activation of latent transforming growth factor-beta secreted by endothelial cells by a novel mechanism". J. Cell Biol. 122 (4): 923–32. doi:10.1083/jcb.122.4.923. PMC 2119591. PMID 8349738.
- Murphy-Ullrich JE, Poczatek M (2000). "Activation of latent TGF-beta by thrombospondin-1: mechanisms and physiology". Cytokine Growth Factor Rev. 11 (1-2): 59–69. doi:10.1016/S1359-6101(99)00029-5. PMID 10708953.
- Huang XZ, Wu JF, Cass D et al. (May 1996). "Inactivation of the integrin beta 6 subunit gene reveals a role of epithelial integrins in regulating inflammation in the lung and skin". J. Cell Biol. 133 (4): 921–8. doi:10.1083/jcb.133.4.921. PMC 2120829. PMID 8666675.
- Bader BL, Rayburn H, Crowley D, Hynes RO (November 1998). "Extensive vasculogenesis, angiogenesis, and organogenesis precede lethality in mice lacking all alpha v integrins". Cell 95 (4): 507–19. doi:10.1016/S0092-8674(00)81618-9. PMID 9827803.
- Shull MM, Ormsby I, Kier AB et al. (October 1992). "Targeted disruption of the mouse transforming growth factor-beta 1 gene results in multifocal inflammatory disease". Nature 359 (6397): 693–9. doi:10.1038/359693a0. PMID 1436033.
- Munger JS, Harpel JG, Giancotti FG, Rifkin DB (September 1998). "Interactions between growth factors and integrins: latent forms of transforming growth factor-beta are ligands for the integrin alphavbeta1". Mol. Biol. Cell 9 (9): 2627–38. doi:10.1091/mbc.9.9.2627. PMC 25536. PMID 9725916.
- Munger JS, Huang X, Kawakatsu H et al. (February 1999). "The integrin alpha v beta 6 binds and activates latent TGF beta 1: a mechanism for regulating pulmonary inflammation and fibrosis". Cell 96 (3): 319–28. doi:10.1016/S0092-8674(00)80545-0. PMID 10025398.
- Kulkarni AB, Huh CG, Becker D et al. (January 1993). "Transforming growth factor β 1 null mutation in mice causes excessive inflammatory response and early death". Proc. Natl. Acad. Sci. U.S.A. 90 (2): 770–4. doi:10.1073/pnas.90.2.770. PMC 45747. PMID 8421714.
- Taylor AW (January 2009). "Review of the activation of TGF-beta in immunity". J. Leukoc. Biol. 85 (1): 29–33. doi:10.1189/jlb.0708415. PMC 3188956. PMID 18818372.
- Mu D, Cambier S, Fjellbirkeland L et al. (April 2002). "The integrin alpha(v)beta8 mediates epithelial homeostasis through MT1-MMP-dependent activation of TGF-beta1". J. Cell Biol. 157 (3): 493–507. doi:10.1083/jcb.200109100. PMC 2173277. PMID 11970960.
(Circulation. 2009;120:S1048.) © 2009 American Heart Association, Inc. Abstract 5095: The Role of Circulating Transforming Growth Factor-β in Vascular Ehlers-Danlos Syndrome: Implications for Drug Therapy Florian S Schoenhoff1; Benjamin F Griswold2; Peter Matt3; Leslie J Sloper4; Michiyo Yamazaki5; Olga D Carlson6; Harry C Dietz7; Jennifer E Van Eyk7; Nazli B McDonnell