組織プラスミノーゲンアクチベータ 組織プラスミノゲンアクチベータ tissue plasminogen activator
出典(authority):フリー百科事典『ウィキペディア(Wikipedia)』「2014/01/25 18:58:24」(JST)
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組織プラスミノーゲン活性化因子(tissue plasminogen activator:略称 tPA または PLAT)は、線溶系に関与するセリンプロテアーゼの1種(EC 3.4.21.68)である。ウロキナーゼ(uPA)と同じく、プラスミノーゲンを活性化することでフィブリンを分解させ、血栓溶解剤として塞栓症および血栓性疾患(心筋梗塞・脳梗塞)の治療に使われる。組み換え型tPA(rtPA)も用いられている。
血管内皮細胞から分泌される。ウロキナーゼと同様に、1本鎖tPA(前駆体)として作られ、プラスミン等により開裂されて活性の高い2本鎖tPA(ジスルフィド結合でつながっている)となるが、1本鎖tPAも活性を有する。プラスミノーゲンを活性化し、活性型のプラスミンを生成する。プラスミンは血栓のフィブリンを溶解するセリンプロテアーゼであり、また細胞外基質の分解にも関与する。tPAは凝固線溶系において、1本鎖型のプラスミノーゲンを開裂し2本鎖型のプラスミンにする。このプラスミンがトロンビンを分解し血栓を溶解する。また細胞外基質の分解を通じて細胞移動やがんの転移にも関与する。
この項目は、医学に関連した書きかけの項目です。この項目を加筆・訂正などしてくださる協力者を求めています(プロジェクト:医学/Portal:医学と医療)。 |
この項目は、薬学に関連した書きかけの項目です。この項目を加筆・訂正などしてくださる協力者を求めています(プロジェクト:薬学/Portal:医学と医療)。 |
Plasminogen activator, tissue | |||||||||||||
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PDB rendering based on 1a5h. |
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Identifiers | |||||||||||||
Symbols | PLAT; T-PA; TPA | ||||||||||||
External IDs | OMIM: 173370 MGI: 97610 HomoloGene: 717 ChEMBL: 1873 GeneCards: PLAT Gene | ||||||||||||
EC number | 3.4.21.68 | ||||||||||||
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RNA expression pattern | |||||||||||||
More reference expression data | |||||||||||||
Orthologs | |||||||||||||
Species | Human | Mouse | |||||||||||
Entrez | 5327 | 18791 | |||||||||||
Ensembl | ENSG00000104368 | ENSMUSG00000031538 | |||||||||||
UniProt | P00750 | P11214 | |||||||||||
RefSeq (mRNA) | NM_000930 | NM_008872 | |||||||||||
RefSeq (protein) | NP_000921 | NP_032898 | |||||||||||
Location (UCSC) | Chr 8: 42.03 – 42.07 Mb |
Chr 8: 22.76 – 22.78 Mb |
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PubMed search | [1] | [2] | |||||||||||
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Tissue plasminogen activator (abbreviated tPA or PLAT) is a protein involved in the breakdown of blood clots. It is a serine protease (EC 3.4.21.68) found on endothelial cells, the cells that line the blood vessels. As an enzyme, it catalyzes the conversion of plasminogen to plasmin, the major enzyme responsible for clot breakdown. Because it works on the clotting system, tPA is used in clinical medicine to treat embolic or thrombotic stroke. Use is contraindicated in hemorrhagic stroke and head trauma.
tPA may be manufactured using recombinant biotechnology techniques. tPA created this way may be referred to as recombinant tissue plasminogen activator (rtPA).
tPA is used in some cases of diseases that feature blood clots, such as pulmonary embolism, myocardial infarction, and stroke, in a medical treatment called thrombolysis. The most common use is for ischemic stroke. It can either be administered systemically, in the case of acutemyocardial infarction, acute ischemic stroke, and most cases of acute massive pulmonary embolism, or administered through an arterial catheter directly to the site of occlusion in the case of peripheral arterial thrombi and thrombi in the proximal deep veins of the leg.[1]
There is significant debate regarding recombinant tPA's effectiveness in ischemic stroke. There have been twelve relevant, large scale, high-quality trials or rtPA in acute ischemic stroke. One common complaint about these studies is that they all have authors with significant conflicts of interest such as financial ties to Genentech, which manufactures tPA. A prominent meta-analysis of these trials concluded that rtPA given within 6 hours of a stroke significantly increased the odds of being alive and independent at final follow-up, particularly in patients treated within 3 hours. However, there was an excess of mortality in treated patients in the first week after the event, mostly from intracranial haemorrhage, and no reduction in mortality by the trials' final follow-up.[2]
The NNT Group on evidence-based medicine concluded that it was inappropriate to combine these twelve trials into a single analysis, because of substantial clinical heterogeneity (i.e., variations in study design, setting, and population characteristics).[3] Examining each study individually, the NNT group noted that two of these studies showed benefit to patients given tPA (and that, using analytical methods that they think flawed); four studies showed harm and had to be stopped before completion; and the remaining studies showed neither benefit nor harm. On the basis of this evidence, the NNT Group recommended against the use of tPA in acute ischaemic stroke.[3]
It has been suggested that if tPA is effective in ischemic stroke, it must be administered as early as possible after the onset of stroke symptoms.[2][4] Indeed, tPA has become widely considered standard of care in acute ischemic stroke, so long as the patient presents soon after the onset of stroke symptoms.[4] Many national guidelines including the AHA have interpreted this cohort of studies as suggesting that there are specific subgroups who may benefit from tPA and thus recommend its use within a limited time window after the event. Protocol guidelines require its use intravenously within the first three hours of the event, after which its detriments may outweigh its benefits. For example, the Canadian Stroke Network guideline states "All patients with disabling acute ischemic stroke who can be treated within 4.5 hours of symptom onset should be evaluated without delay to determine their eligibility for treatment" with tPA.[5] Because of this, only about 3% of people qualify for this treatment, since most patients do not seek medical assistance quickly enough.[citation needed] Similarly in the United States, the window of administration used to be 3 hours from onset of symptoms, but the newer guidelines also recommend use up to 4.5 hours after symptom onset.[6] tPA appears to show benefit not only for large artery occlusions but also for lacunar strokes. Since tPA dissolves blood clots, there is risk of hemorrhage with its use.
However, the NNT Group notes that the case for this time window arises largely from analysis of two trials: NINDS-2 and subgroup results from IST-3. "However, presuming that early (0-3h) administration is better than later administration (3-4.5h or 4.5-6h) the subgroup results of IST-3 suggest an implausible biological effect in which early administration is beneficial, 3-4.5h administration is harmful, and 4.5-6h administration is again beneficial."[3] Indeed, even the original publication of the IST-3 trial found that time-window effects were not significant predictors of outcome (p=0.61).[7]
Use of tPA in the United States in treatment of patients who are eligible for its use, no contra-indications and arrival at the treating facility less than 3 hours after onset of symptoms, is reported to have doubled from 2003 to 2011. Use on patients with mild deficits, of nonwhite race/ethnicity, and oldest old age increased. However, many patients who were eligible for treatment were not treated.[8][9]
tPA has also been given to patients with acute ischemic stroke above age 90 years old. Although a small fraction of patients 90 years and above treated with tPA for acute ischemic stroke recover, most patients have a poor 30-day functional outcome or die.[10] Nonagenarians may do as well as octogenarians following treatment with IV-tPA for acute ischemic stroke.[11] In addition, people with frostbite treated with tPA had fewer amputations than those not treated with tPA.[12]
Recombinant tissue plasminogen activators (r-tPAs) include alteplase, reteplase, and tenecteplase (TNKase).[1]
Activase (Alteplase) is FDA-approved for treatment of myocardial infarction with ST-elevation (STEMI), acute ischemic stroke (AIS), acute massive pulmonary embolism, and central venous access devices (CVAD).[1]
Reteplase is FDA-approved for acute myocardial infarction, where it has more convenient administration and faster thrombolysis than alteplase.[1]
Tenecteplase is also indicated in acute myocardial infarction, showing fewer bleeding complications but otherwise similar mortality rates after one year compared to alteplase.[1]
Additional r-tPAs, such as desmoteplase, are under clinical development.
Tissue plasminogen activator has been shown to interact with:
tPA and plasmin are the key enzymes of the fibrinolytic pathway in which tPA mediated plasmin generation occurs. To be specific, tPA cleaves the zymogen plasminogen at its Arg561 - Val562 peptide bond, into the serine protease plasmin.
Increased enzymatic activity causes hyperfibrinolysis, which manifests as excessive bleeding. Decreased activity leads to hypofibrinolysis which can result in thrombosis or embolism.
Tissue plasminogen activator also plays a role in cell migration and tissue remodeling.
Tissue plasminogen activator is a protein encoded by the PLAT gene, which is located on chromosome 8. The primary transcript produced by this gene undergoes alternative splicing, producing three distinct messenger RNAs.
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国試過去問 | 「104B061」「104B060」「110D023」「104B059」「110F029」「109I079」「112D072」「107A033」「110D028」「114B038」「109I021」「107I035」「104B037」 |
リンク元 | 「脳梗塞」「プラスミノーゲンアクチベーターインヒビター」「プラスミン」「組織プラスミノゲンアクチベータ」「プラスミノゲン」 |
関連記事 | 「PA」「ting」「T」「P」 |
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アテローム血栓性脳梗塞 | ラクナ梗塞 | 心原性脳塞栓 | |
発症機序 | 血栓性 塞栓性 血行力学性 |
血栓症 | 塞栓性 |
好発年齢 | 高齢者 | 高齢者 | 若年者もあり |
発症時刻 | 起床時 | 覚醒時 | 日中活動時 |
発症様式 | 緩徐進行 | 比較的緩徐進行 | 突発的 |
意識障害 | 軽度 | なし | しばしば高度 |
大脳皮質症状 | 時にあり | なし | あり |
基礎疾患 | 高血圧 糖尿病 高脂血症 |
高血圧 | 心疾患 |
治療 YN.J-81 | |||
時期 | ラクナ梗塞 | アテローム血栓性脳梗塞 | 心原性塞栓症 |
超急性期(~3時間) | 血栓溶解療法(t-PA静注) | ||
超急性期+急性期 | 脳保護薬(エダラボン) | ||
急性期(~2週間) | 抗血小板療法(アスピリン) | ||
抗血小板療法(オザグレル) | 抗凝固療法(ヘパリン、ワルファリン) | ||
選択的トロンビン阻害薬(アルガトロバン) | |||
抗浮腫療法(グリセロール) |
プラスミノーゲン活性化因子インヒビター plasminogen activator inhibitor
プラスミノーゲンアクチベーターインヒビター : 約 42,500 件 プラスミノゲンアクチベーターインヒビター : 約 12,500 件 プラスミノーゲン活性化因子インヒビター : 約 9,050 件 プラスミノゲン活性化因子インヒビター : 60 件 プラスミノーゲンアクチベーターインヒビター PAI : 約 26,500 件 プラスミノゲンアクチベーターインヒビター PAI : 約 8,890 件 プラスミノーゲン活性化因子インヒビター PAI : 約 3,150 件 プラスミノゲン活性化因子インヒビター PAI : 41 件
-プラスミノーゲン
.