Structure dissection of human progranulin identifies well-folded granulin/epithelin modules with unique functional activities
Structure dissection of human progranulin identifies well-folded granulin/epithelin modules with unique functional activities
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DOI：
10.1110/ps.073295308
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发表时间：
2008-04-01
期刊：
影响因子：
8
通讯作者：
Ni, Feng
中科院分区：
文献类型：
--
作者：
Tolkatchev, Dmitri;Malik, Suneil;Ni, Feng
颗粒蛋白前体是一种分泌性蛋白质，在胚胎发育、宿主防御和创伤修复等生理和病理过程中具有重要功能。颗粒蛋白前体基因的常染色体显性突变导致额颞叶痴呆，而颗粒蛋白前体的过度表达促进了一系列肿瘤的侵袭性进展，包括乳腺癌和脑肿瘤。在结构上，颗粒蛋白前体由颗粒蛋白/上皮蛋白模块（GEM）的七个半串联重复序列组成，其中几个已被分离为离散的6-kDa GEM肽。我们已经表达了所有七个人的GEM使用重组DNA在大肠杆菌。高分辨率NMR表明，只有三个GEM，hGrnA，hGrnC和hGrnF，在溶液中含有相对明确的三维结构，而其他主要是结构不良的二硫化物异构体的混合物。hGrnA、hGrnC和hGrnF的三维结构在其N-末端亚结构域中含有两个稳定的β-发夹堆叠，但显示出更灵活的C-末端亚结构域。有趣的是，在结构良好的GEM中，hGrnA表现出对乳腺癌细胞系的有效生长抑制，而hGrnF是刺激性的。折叠不良的肽要么是弱抑制性的，要么没有活性。功能活性和结构良好的人hGrnA提供了一个独特的机会，详细的结构-功能研究这些重要的GEM蛋白作为哺乳动物生长因子的新成员。
Progranulin is a secreted protein with important functions in several physiological and pathological processes, such as embryonic development, host defense, and wound repair. Autosomal dominant mutations in the progranulin gene cause frontotemporal dementia, while overexpression of progranulin promotes the invasive progression of a range of tumors, including those of the breast and the brain. Structurally, progranulin consists of seven-and-a-half tandem repeats of the granulin/epithelin module ( GEM), several of which have been isolated as discrete 6-kDa GEM peptides. We have expressed all seven human GEMs using recombinant DNA in Escherichia coli. High-resolution NMR showed that only the three GEMs, hGrnA, hGrnC, and hGrnF, contain relatively well-defined three-dimensional structures in solution, while others are mainly mixtures of poorly structured disulfide isomers. The three-dimensional structures of hGrnA, hGrnC, and hGrnF contain a stable stack of two beta-hairpins in their N-terminal subdomains, but showed a more flexible C-terminal subdomain. Interestingly, of the well-structured GEMs, hGrnA demonstrated potent growth inhibition of a breast cancer cell line, while hGrnF was stimulatory. Poorly folded peptides were either weakly inhibitory or without activity. The functionally active and structurally well-characterized human hGrnA offers a unique opportunity for detailed structure-function studies of these important GEM proteins as novel members of mammalian growth factors.