人類Thioredoxin對淋巴細胞生長刺激機制之研究

Abstract

Thioredoxin ( TRX ) 是細胞內一種具有雙硫的酵素，存在於所有的原 核及真核細胞中。它依據其雙硫鍵而具有氧化還原的活性，可參與許多細 胞的還原反應。人類的TRX已經被證實和一種叫做成人型T細胞白血病衍生 因子 ( Adult T cell leukemia-derived factor；ADF ) 的血癌細胞生 長因子相同。ADF/TRX是第二型間白素受器 a 鏈 ( Interleukin-2 receptor a chain；IL-2R / p55(Tac) ) 的引發者。它經由促進IL-2R / Tac基因的轉錄來促進IL-2R "2LY5蛋白質的表現。另外，在被Epstein- Barr病毒 ( EBV ) 轉型的B細胞株3B6內，也發現了一種類似於第一型間 白素 ( IL) 之生長因子，經證實這種生長因子即為ADF，也就是人類的 TRX。在細胞內，TRX的增殖和嗜淋巴球性的病毒如人類T細胞嗜淋巴球性 逆病毒 ( human lymphotropic virus type I；HTLV-I ) 或Epstein- Barr virus ( EBV ) 感染而造成的細胞轉型有關。在被HTLV-I 轉型的細 胞株內，TRX蛋白質的表現是依據細胞週期而改變，並且在DNA合成期 ( S phase ) 達到最高點。所以，TRX可能參與了病毒造成的細胞轉型及增生 的過程。我們先從TRX的互補DNA ( cDNA ) 內選殖出TRX的基因，進而將 之大量表現及純化。得到TRX蛋白質之後，我們比較了TRX對正常週邊血液 淋巴細胞以及有呶病毒感染的B及T細胞株之促進生長作用。我們發現，不 論B細胞或T細胞，病毒感染過的細胞株更容易被TRX刺激而增生。然而， 正常週邊血液淋巴細胞卻無法被TRX刺激而活化增生。此外，我們也利用 蛋白激酵素C ( protein kinase C；PKC ) 以及PTK ( protein tyrosine kinase ) 的抑制劑發現PKC 抑制劑可抑制TRX促進之T細胞增生；而PTK抑 制劑則無法抑制TRX促進之B細胞增生，但是利用西方墨點法則可於病毒感 染之B細胞株及被TRX刺激之B細胞株見到多出之phosphotyrosine蛋白質。 Thioredoxin (TRX), known to be present in all eukaryotic and prokaryotic organisms, is an intracellular dithiol enzyme. It exerts dithiol-disulfide oxidoreductase activity. Human TRX has been shown to be identical to a leukemic cell growth factor ADF ( Adult T cell leukemia-derived factor). ADF/TRX is an inducer of interleukin-2 receptor a chain, IL-2R/p55(Tac). It enhances the expression of IL-2R/Tac through enhanced transcription of the IL-2R/Tac gene. The production of TRX is enhanced or induced in assoction with the transformation by lymphotropic viruses such as human T-lymphotropic virus type I ( HTLV-I ) or Epstein- Barr virus ( EBV ). In HTLV-I transformed cell lines, the expression of ADF/TRX depends on the cell cycle and peaks at S phase. These are indications of the possible involvement of TRX in virus-related transformation of cells and their autocrine growth.We have cloned human TRX gene, overexpressed and purified the protein. In order to understand the relationship between TRX and virus-related deases, we compared the growth promotion effects of TRX in peripheral blood lymphocyte with that of virus-negative and virus-positive B and T lymphocytes. The proliferation effect induced by TRX is larger in virus-positive than that in the virus-negative B and T lymphocytes. TRX can not provoke peripheral blood lymphocytes from resting to active state. By using specific inhibitors, the cellular proliferation induced by TRX was inhibited by protein kinase C ( PKC ) inhibitor in T lymphocytes and was not inhibed by protein tyrosine kinase ( PTK ) inhibitor in B lymphocytes.