Plasminogen activator inhibitor-1 (PAI-1) also known as endothelial plasminogen activator inhibitor or serpin E1 is a protein that in humans is encoded by the SERPINE1gene. Elevated PAI-1 is a risk factor for thrombosis and atherosclerosis[1]
The other PAI, plasminogen activator inhibitor-2 (PAI-2) is secreted by the placenta and only present in significant amounts during pregnancy. In addition, proteasenexin acts as an inhibitor of tPA and urokinase. PAI-1, however, is the main inhibitor of the plasminogen activators.
The PAI-1 gene is SERPINE1, located on chromosome 7 (7q21.3-q22). There is a common polymorphism known as 4G/5G in the promoter region. The 5G allele is slightly less transcriptionally active than the 4G.
Function
PAI-1's main function entails the inhibition of urokinase plasminogen activator (uPA), an enzyme responsible for the cleavage of plasminogen to form plasmin. Plasmin mediates the degradation of the extracellular matrix either by itself or in conjunction with matrix metalloproteinases. In this scenario, PAI-1 inhibits uPA via active site binding, preventing the formation of plasmin. Additional inhibition is mediated by PAI-1 binding to the uPA/uPA receptor complex, resulting in the latter's degradation.[2] Thus, PAI can be said to inhibit the serine proteases tPA and uPA/urokinase, and hence is an inhibitor of fibrinolysis, the physiological process that degrades blood clots. In addition, PAI-1 inhibits the activity of matrix metalloproteinases, which play a crucial role in invasion of malignant cells through the basal lamina.
Congenital deficiency of PAI-1 has been reported; as fibrinolysis is not suppressed adequately, it leads to a hemorrhagic diathesis (a tendency to hemorrhage).
PAI-1 is present in increased levels in various disease states (such as a number of forms of cancer), as well as in obesity and the metabolic syndrome. It has been linked to the increased occurrence of thrombosis in patients with these conditions.
In inflammatory conditions in which fibrin is deposited in tissues, PAI-1 appears to play a significant role in the progression to fibrosis (pathological formation of connective tissue). Presumably, lower PAI levels would lead to less suppression of fibrinolysis and conversely a more rapid degradation of the fibrin.
Angiotensin II increases synthesis of plasminogen activator inhibitor-1, so it accelerates the development of atherosclerosis.
↑Boncela J, Papiewska I, Fijalkowska I, Walkowiak B, Cierniewski CS (September 2001). "Acute phase protein alpha 1-acid glycoprotein interacts with plasminogen activator inhibitor type 1 and stabilizes its inhibitory activity". The Journal of Biological Chemistry. 276 (38): 35305–11. doi:10.1074/jbc.M104028200. PMID11418606.
Further reading
Mimuro J (May 1991). "[Type 1 plasminogen activator inhibitor: its role in biological reactions]". [Rinshō Ketsueki] the Japanese Journal of Clinical Hematology. 32 (5): 487–9. PMID1870265.
Binder BR, Christ G, Gruber F, Grubic N, Hufnagl P, Krebs M, Mihaly J, Prager GW (April 2002). "Plasminogen activator inhibitor 1: physiological and pathophysiological roles". News in Physiological Sciences. 17: 56–61. PMID11909993.
Eddy AA (August 2002). "Plasminogen activator inhibitor-1 and the kidney". American Journal of Physiology. Renal Physiology. 283 (2): F209–20. doi:10.1152/ajprenal.00032.2002. PMID12110504.
Wang J, Li J, Liu Q (August 2005). "Association between platelet activation and fibrinolysis in acute stroke patients". Neurosci. Lett. 384 (3): 305–9. doi:10.1016/j.neulet.2005.04.090. PMID15916851.
Schroeck F, Arroyo de Prada N, Sperl S, Schmitt M, Viktor M (2003). "Interaction of plasminogen activator inhibitor type-1 (PAI-1) with vitronectin (Vn): mapping the binding sites on PAI-1 and Vn". Biological Chemistry. 383 (7–8): 1143–9. doi:10.1515/BC.2002.125. PMID12437099.
Gils A, Declerck PJ (March 2004). "The structural basis for the pathophysiological relevance of PAI-I in cardiovascular diseases and the development of potential PAI-I inhibitors". Thrombosis and Haemostasis. 91 (3): 425–37. doi:10.1160/TH03-12-0764. PMID14983217.
Durand MK, Bødker JS, Christensen A, Dupont DM, Hansen M, Jensen JK, Kjelgaard S, Mathiasen L, Pedersen KE, Skeldal S, Wind T, Andreasen PA (March 2004). "Plasminogen activator inhibitor-I and tumour growth, invasion, and metastasis". Thrombosis and Haemostasis. 91 (3): 438–49. doi:10.1160/TH03-12-0784. PMID14983218.
Harbeck N, Kates RE, Gauger K, Willems A, Kiechle M, Magdolen V, Schmitt M (March 2004). "Urokinase-type plasminogen activator (uPA) and its inhibitor PAI-I: novel tumor-derived factors with a high prognostic and predictive impact in breast cancer". Thrombosis and Haemostasis. 91 (3): 450–6. doi:10.1160/TH03-12-0798. PMID14983219.
Hertig A, Rondeau E (January 2004). "Plasminogen activator inhibitor type 1: the two faces of the same coin". Current Opinion in Nephrology and Hypertension. 13 (1): 39–44. doi:10.1097/00041552-200401000-00006. PMID15090858.
Hoekstra T, Geleijnse JM, Schouten EG, Kluft C (May 2004). "Plasminogen activator inhibitor-type 1: its plasma determinants and relation with cardiovascular risk". Thrombosis and Haemostasis. 91 (5): 861–72. doi:10.1160/TH03-08-0546. PMID15116245.
Lijnen HR (January 2005). "Pleiotropic functions of plasminogen activator inhibitor-1". Journal of Thrombosis and Haemostasis. 3 (1): 35–45. doi:10.1111/j.1538-7836.2004.00827.x. PMID15634264.
De Taeye B, Smith LH, Vaughan DE (April 2005). "Plasminogen activator inhibitor-1: a common denominator in obesity, diabetes and cardiovascular disease". Current Opinion in Pharmacology. 5 (2): 149–54. doi:10.1016/j.coph.2005.01.007. PMID15780823.
Dellas C, Loskutoff DJ (April 2005). "Historical analysis of PAI-1 from its discovery to its potential role in cell motility and disease". Thrombosis and Haemostasis. 93 (4): 631–40. doi:10.1160/TH05-01-0033. PMID15841306.
Könsgen D, Mustea A, Lichtenegger W, Sehouli J (June 2005). "[Role of PAI-1 in gynaecological malignancies]". Zentralblatt für Gynäkologie. 127 (3): 125–31. doi:10.1055/s-2005-836407. PMID15915389.
Hermans PW, Hazelzet JA (November 2005). "Plasminogen activator inhibitor type 1 gene polymorphism and sepsis". Clinical Infectious Diseases. 41 Suppl 7: S453–8. doi:10.1086/431996. PMID16237647.
Alessi MC, Poggi M, Juhan-Vague I (June 2007). "Plasminogen activator inhibitor-1, adipose tissue and insulin resistance". Current Opinion in Lipidology. 18 (3): 240–5. doi:10.1097/MOL.0b013e32814e6d29. PMID17495595.
External links
The MEROPS online database for peptidases and their inhibitors: I04.020