多胺類修飾在細胞凋亡過程中之角色

Abstract

細胞凋亡是遍存於自然界的細胞自我死亡現象，許多作用與如何被調控的機制仍待證明。轉穀氨醯胺酶II、多胺類和多胺類修飾是否牽涉在細胞凋亡過程中，以及被多胺類所修飾受質的身分，一直都是許多文獻想研究的重點。 本研究中，我們使用實驗室製備的抗精胺抗體確定了在 staurosporine 所誘發 HeLa 細胞的細胞凋亡過程中，多胺類修飾是被轉穀氨醯胺酶II的轉醯胺功能和多胺類所調節；且隨著細胞凋亡的情況加劇，多胺類修飾更明顯。加入轉穀氨醯胺酶II的抑制劑：cystamine 後，轉醯胺反應會被抑制，多胺類修飾程度降低，細胞死亡率亦下降，因此判斷轉穀氨醯胺酶II的轉醯胺功能是能促進 HeLa 細胞凋亡。另外發現，細胞內多胺類的含量降低會使轉穀氨醯胺酶II的轉醯胺反應提高，加速細胞凋亡的發生，判斷多胺類具有保護 HeLa 細胞的角色。細胞凋亡過程中，被多胺類所主要修飾的兩個小分子蛋白質（分子量約為 14 kDa 和 20 kDa）的身分也是我們接續研究的重點。 本實驗室之前以蛋白質純化及質譜儀鑑定發現在小鼠組織中 HtrA2/Omi 蛋白質能與精胺結合，此蛋白質為促進細胞凋亡的重要蛋白質。本研究在 HeLa 細胞內確定了 HtrA2/Omi 蛋白質能被多胺類修飾，但被多胺類修飾的生理意義仍須進一步的探討與釐清。

Apoptosis is an autonomous cell-death phenomenon, whose underlying mecha-nisms remain to be investigated. The involvement of transglutaminse II, polyamine and polyamination in apoptosis, and identities of polyamine-modified proteins have been vigorously studied in recent years. In this study, we have generated an anti-spermine antiserum and confirm that pol-yamination is regulated by the transamidation activity of transglutaminse II and poly-amine in staurosporine-induced apoptosis in HeLa cells. The increase in polyamination in HeLa cells induced by staurosporine is dose-dependent. Treatment with cystamine, an inhibitor of transglutaminse II, decreased the transamidation activity, polyamination and cell death of HeLa cells. This suggests the transamidation activity of transglutaminse II is pro-apoptosis in HeLa cells. Depletion of spermine level in HeLa cells accelerates apoptosis; this suggests the role of polyamine in HeLa cells is pro-cell survival. The identification of two major polyamine-modified proteins, molecular weight of about 14 and 20 kDa, in apoptosis are in progress. We have previously identified HtrA2/Omi, an important pro-apoptosis protein, as a spermine-binding protein. In this study, we confirm HtrA2/Omi is a polyamine-modified protein in HeLa cells, but the physiological function of polyamination of this protein requires further investigation.