免疫相关GTP结合蛋白2的亚细胞定位分析

目的 对免疫相关GTP结合蛋白2(GTPase of immunity-associated protein 2,GIMAP2)进行亚细胞定位分析,为深入研究GIMAP2蛋白的功能奠定基础.方法: 使用国家生物技术信息中心(National Center for Biotechnology Information,NCBI)数据库查询获取GIMAP2的蛋白序列,再利用生物信息学在线分析工具对GIMAP2蛋白的跨膜结构,核定位信号(nuclear localization signal,NLS),核输出信号(nuclear export signal,NES)及亚细胞定位进行分析预测.采用PCR技术扩增GIMAP2基因片段,并插入至pQCXIP-mCherry-N1表达载体,用氨苄青霉素抗性筛选阳性克隆.测序正确的重组质粒pQCXIP-GIMAP2-mCherry经过提取,纯化步骤后,与逆转录病毒包装质粒VSVG,Gag/Pol在脂质体介导下共同转入HEK293FT细胞中进行病毒包装.转染48 h后收集病毒上清,直接感染人乳腺癌细胞系MDA-MB-436.使用免疫荧光染色方法检测内,外源性GIMAP2在MDA-MB-436胞内表达定位情况.使用绿色荧光化学染料分别标记稳定表达GIMAP2-mCherry融合蛋白的MDA-MB-436活细胞中的线粒体,内质网,脂滴,在超分辨率显微镜N-SIM下观察其与红色荧光的GIMAP2蛋白的定位情况.结果: 生物信息学分析数据显示,由337个氨基酸组成的GIMAP2蛋白在羧基端可能有2个跨膜螺旋结构,其中跨膜螺旋含预期氨基酸数为 40~41个,紧随跨膜螺旋结构之后的蛋白结构朝细胞质侧;羧基端第279~281位氨基酸有NES但无NLS;可能定位在内质网.测序结果表明,成功构建表达载体pQCXIP-GIMAP2-mCherry.荧光染色结果证实,GIMAP2-mCherry融合蛋白成功在MDA-MB-436细胞内表达,并与内源性GIMAP2定位一致,分布于内质网和脂滴.结论: 免疫相关GTP结合蛋白2定位于内质网和脂滴,可能与脂代谢相关.

Subcellular localization of GTPase of immunity-associated protein 2

Objective: To analyze the subcellular localization of GTPase of immunity-associated protein 2 (GIMAP2) for the further functional study.Methods: In the study,we first obtained the protein sequences of GTPase of immunity-associated protein 2 (GIMAP2) from National Center for Biotechnology Information (NCBI) database, and then performed a prediction analysis of its transmembrane structure, nuclear localization signal (NLS), nuclear export signal (NES) and subcellular localization through bioinformatics online tools. GIMAP2 gene amplified by PCR was inserted into the expression vector pQCXIP-mCherry-N1 and positive clones were selected by ampicillin resistance. After using methods to extract and purify, the sequenced recombinant plasmid pQCXIP-GIMAP2-mCherry, together with the retroviral packaging plasmids VSVG and Gag/pol, was transferred into HEK293FT cells by liposomes for virus packaging. The virus supernatant was collected 48 h after transfection and directly infected the human breast cancer cell line MDA-MB-436. Immunofluorescence staining was constructed to detect the localization of endogenous and exogenous GIMAP2 in MDA-MB-436 cells. Meanwhile, green fluorescent chemical dyes were used to label mitochondria, endoplasmic reticulum, and lipid droplets in living MDA-MB-436 cells stably expressing the GIMAP2-mCherry fusion protein. Images for the three dye-labeled organelles and GIMAP2-mCherry fusion protein were captured by super-resolution microscope N-SIM.Results: Bioinformatics analysis data showed that GIMAP2 protein composed of 337 amino acids might contain two transmembrane helix (TM) structures at the carboxyl terminus, of which TMs were estimated to contain 40-41 expected amino acids,followed by the residual protein structures toward the cytoplasmic side. NES was located at the 279-281 amino acids of the carboxyl terminus whereas NLS was not found. GIMAP2 might locate in the lumen of the endoplasmic reticulum. Sequencing results indicated that the expression vector pQCXIP-GIMAP2-mCherry was successfully constructed. Fluorescent staining confirmed that GIMAP2-mCherry fusion protein, co-localized well with endogenous GIMAP2, expressed successfully in the endoplasmic reticulum and on the surface of lipid droplets in MDA-MB-436 cells.Conclusion: GIMAP2 localizes in the endoplasmic reticulum and on the surface of LDs, suggesting potential involvement of GIMAP2 in lipid metabolism.