人類血漿蛋白Haptoglobin其結構與活性關係之探討

Abstract

Haptoglobin (Hp)是一種acute phase protein，其在生理上具有各種不同的功能。其中最為人所知的功能是與和自由態的血紅素形成複合物,將該複合物運送到肝臟做代謝，並防止鐵的流失及組織的傷害。在人類族群中，有三種主要的表現型，分別為Hp (1-1), Hp(2-1) 及Hp(2-2) ，其形成的原因是因為不同表現型的Hp上□鍊具有未配對的半胱胺酸，而做成彼此相互交錯結合所導致。根據臨床上的統計資料也顯示了不同表現型和某些疾病也具有相當大的關連性，包括了心血管疾病、自體免疫疾病、發炎反應及惡性腫瘤等。因此，認知不同的表現型可以幫助我們預知疾病的發生，並可根據個人需求來加以量身定做。 在本實驗中，採用基因重組技術，將各種不同基因型及其次單元分別轉殖到Hp-deficient CHO-K1細胞上，使CHO-K1細胞能表現人類的Hp，以模擬Hp在生理學上的行為。經由添加過氧化氫的測試可以清楚地證實帶有Hp基因的CHO-K1細胞，能有效的防止過氧化氫所造成的細胞毒性。另外經由添加血紅素(Hb)的實驗發現，單獨存在Hp的□鍊能夠有效的減少血紅素過氧化活性，而單獨存在的□鍊則會有增強的趨勢。因此可證實Hp在過氧化氫及血紅素存在的情況下，有能力減輕其對細胞所造成的傷害。

Haptoglobin (Hp), an acute phase protein, has different biological functions. The well-known function is hemoglobin (Hb) binding ability, which preventing iron loss and tissue damage, and transport the Hp-Hb complex to liver for regeneration. In nature, there are three major phenotypes – Hp (1-1), Hp(2-1) and Hp(2-2) in human due to free cysteine in different α chain to form varied cross-linking pattern. The clinical statistics demonstrate that the particular phenotype has been associated with a variety of disorders, including cardiovascular disease, autoimmune disease, inflammatory and malignancy etc. So, knowledge of phenotype can therefore aid in the prognosis of disease and allow treatment to be better tailored to personalize medicine. The aim of this study was to investigate the effects of the each type and subunit assembling of haptoglobin on physiological role and antioxidant activity in CHO-K1 cells. First, haptoglobin cDNA was cloned from HepG2 cell line and constructed into mammalian expression vector : pcDNA3.1 and driven by CMV promoter. The DNA were transfected into CHO-K1 cells and selected by G418. Hydrogen peroxide is a kind of free radical and can induced cell death. The CHO-K1 cells would survive if they got the haptoglobin cDNA, whenever which types or subunits. The CHO-K1 cells could also inhibit hemoglobin peroxidation activity when they carry the α1 or α2 chain gene, but enhance when carry the β chain. In conclusion, the haptoglobin have the antioxidant activity.