Genetic and functional studies of phosphatidyl-inositol 4-kinase type IIIα.
Genetic and functional studies of phosphatidyl-inositol 4-kinase type IIIα.
复制标题
磷脂酰肌醇4激酶IIIα型的遗传和功能研究。
DOI：
10.1016/j.bbalip.2011.04.013
复制
发表时间：
2011
期刊：
影响因子：
--
通讯作者：
Balla,Tamas
中科院分区：
文献类型：
--
作者：
Szentpetery,Zsofia;Szakacs,Gergely;Bojjireddy,Naveen;Tai,AndrewW;Balla,Tamas
磷脂酰肌醇4-激酶Ⅲ a（PI 4KIII α）是哺乳动物四种PI 4-激酶之一，催化多聚磷酸肌醇合成的第一个关键步骤。PI 4KIII α与ER出口位点的调节和质膜磷酸肌醇的合成有关，最近的研究也揭示了其在肝脏中丙型肝炎病毒复制中的重要性。哺乳动物PI 4 KIII α的两种亚型已在GenBank中描述和注释：一种较大的约230 kDa（亚型2）和一种较短的剪接变体，仅含有约97 kDa C-末端，包括催化结构域（亚型1）。然而，对人组织和癌细胞的北方分析显示，除了原红白血病细胞系K562外，其仅含有约7.5 kb的单个转录物，该细胞系含有显著更高水平的7.5 kb转录物，沿着有2.4、3.5和4.2 kb大小的较小转录物。生物信息学分析还证实了K562细胞中PI 4 KIII α转录本的高拷贝数，沿着几个基因位于Chr 22的相同区域，包括两个假基因，其覆盖了编码亚型1的大多数外显子，与染色体扩增一致。一组针对PI 4KIII α C-末端一半内的肽的多克隆抗体在COS-7细胞或K562细胞中均未能检测到较短的亚型1。此外，表达的cDNA编码亚型1产生的蛋白质约97 kDa，没有催化活性，未能挽救丙型肝炎病毒复制。这些数据引起了人们对PI 4KIII α作为Chr 22 q11（受染色体不稳定性影响的区域）中发现的基因之一的关注，但并未证实存在功能相关的短型PI 4KIII α。
Phosphatidylinositol 4-kinase type IIIa (PI4KIIIα) is one of four mammalian PI 4-kinases that catalyzes the first committed step in polyphosphoinositide synthesis. PI4KIIIα has been linked to regulation of ER exit sites and to the synthesis of plasma membrane phosphoinositides and recent studies have also revealed its importance in replication of the Hepatitis C virus in liver. Two isoforms of the mammalian PI4KIIIα have been described and annotated in GenBank: a larger, ~ 230 kDa (isoform 2) and a shorter splice variant containing only the ~ 97 kDa C-terminus that includes the catalytic domain (isoform 1). However, Northern analysis of human tissues and cancer cells showed only a single transcript of ~ 7.5 kb with the exception of the proerythroleukemia line K562, which contained significantly higher level of the 7.5 kb transcript along with smaller ones of 2.4, 3.5 and 4.2 kb size. Bioinformatic analysis also confirmed the high copy number of PI4KIIIα transcript in K562 cells along with several genes located in the same region in Chr22, including two pseudogenes that cover most exons coding for isoform 1, consistent with chromosome amplification. A panel of polyclonal antibodies raised against peptides within the C-terminal half of PI4KIIIα failed to detect the shorter isoform 1 either in COS-7 cells or K562 cells. Moreover, expression of a cDNA encoding isoform 1 yielded a protein of ~ 97 kDa that showed no catalytic activity and failed to rescue hepatitis C virus replication. These data draw attention to PI4KIIIα as one of the genes found in Chr22q11, a region affected by chromosomal instability, but do not substantiate the existence of a functionally relevant short form of PI4KIIIα.