HAP蛋白疏水区的聚合功能及其与细胞凋亡的关系

Polymerization of HAP Hydrophobic Regions and Its Relation with Apoptosis

asy和hap是一对新的细胞凋亡诱发基因 .二者单独转染细胞均能诱发细胞凋亡 ,能在酵母和哺乳动物细胞中形成同源二聚体 ,二者共转染酵母和哺乳动物细胞能形成异源二聚体 .同源二聚体诱发细胞凋亡 ,异源二聚体降低同源二聚体诱发细胞凋亡的活性 .氨基酸序列表明 ,HAP(homologousofASYprotein)含有内质网挽回模体 (KKKAE)、第一疏水区和第二疏水区 .对 3个功能区的缺失突变体研究显示 ,缺失内质网定位信号的HAPΔERS蛋白保留着同源聚合和与ASY异源聚合的能力 ,而分别缺失第一、第二疏水区的突变体HAPΔ4 8 139、HAPΔ15 7 2 18则丧失以上功能 ;通过流式计数法计算 3个缺失突变体诱发细胞凋亡比率 ,用生物统计学方法说明不同的比率与HAP诱发细胞凋亡的比率相比都有显著差异 .说明内质网定位信号、疏水区在HAP蛋白的诱发细胞凋亡过程中起重要作用 ,进一步揭示了HAP诱发细胞凋亡的机制 .

Asy and hap is a pair of novel apoptosis inducing gene. When they are transfected into cells separately, each of them could induce apoptosis and form homodimer in yeast and mammalian cells. When they are cotransfected into cells, they could form heterodimer in yeast and mammalian cells. Homodimer induces apoptosis, heterodimer decreases the inducing apoptosis activity of homodimer. Analysis of amino acid sequence indicated homologous of ASY protein(HAP) having ER retrieval motif (KKKAE) and two highly hydrophobic regions. The study of three mutants indicated that HAPΔERS, a mutant in which ER retrieval motif was deleted, maintained the function of homodimerization and heterodimerization. The other two mutants, the first and second hydrophobic regions of which were deleted, abolished the functions. The apoptosis ratios of three mutants counted by flow cytometry showed significant difference from the apoptosis ratio of hap with biostatistical method. The result demonstrated ER retrievel motif and hydrophobic regions having important roles in the apoptosis process. It further revealed the mechanism underlying the hap induced apoptosis.