BLOC-3, a protein complex containing the Hermansky-Pudlak syndrome gene products HPS1 and HPS4
BLOC-3, a protein complex containing the Hermansky-Pudlak syndrome gene products HPS1 and HPS4
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DOI：
10.1074/jbc.m301294200
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发表时间：
2003-08-01
影响因子：
4.8
通讯作者：
Bonifacino, JS
中科院分区：
文献类型：
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作者：
Martina, JA;Moriyama, K;Bonifacino, JS
Hermansky-Pudlak综合征（HPS）是一种以溶酶体相关细胞器缺陷为特征的遗传性疾病。HPS是由人类HPS1 - HPS6基因突变引起的，其中大部分基因编码功能未知的蛋白质。在这里，我们报道了人类HPS1和HPS4蛋白是一个名为block -3的复合体的一部分（用于溶酶体相关细胞器复合体3的生物发生）。共免疫沉淀实验表明，表位标记的内源性HPS1和HPS4蛋白在体内相互组装。HPS1。HPS4复合体主要存在于细胞质中，少量存在于细胞膜周围。细胞质部分的粒径排除色谱和沉降速度分析表明，HPS1和HPS4形成中等不对称的蛋白复合物，分子质量接近175 kDa。来自光耳小鼠的hps4缺陷成纤维细胞呈现正态分布和溶酶体膜蛋白Lamp-2的运输，而来自珍珠小鼠的ap -3缺陷成纤维细胞（HPS2）表现出通过质膜运输这种溶酶体蛋白的增加。同样，轻耳成纤维细胞在细胞内囊泡中表现出明显正常的Zn2+积累，而珍珠成纤维细胞则表现出细胞内Zn2+储存减少。综上所述，这些观察结果表明，HPS1和HPS4蛋白是细胞质复合体的组成部分，参与溶酶体相关细胞器的生物发生，其机制与AP-3复合体不同。
The Hermansky-Pudlak syndrome (HPS) is a genetic disorder characterized by defective lysosome-related organelles. HPS results from mutations in either one of six human genes named HPS1 to HPS6, most of which encode proteins of unknown function. Here we report that the human HPS1 and HPS4 proteins are part of a complex named BLOC-3 ( for biogenesis of lysosome-related organelles complex 3). Co-immunoprecipitation experiments demonstrated that epitope-tagged and endogenous HPS1 and HPS4 proteins assemble with each other in vivo. The HPS1 . HPS4 complex is predominantly cytosolic, with a small amount being peripherally associated with membranes. Size exclusion chromatography and sedimentation velocity analyses of the cytosolic fraction indicate that HPS1 and HPS4 form a moderately asymmetric protein complex with a molecular mass of similar to 175 kDa. HPS4-deficient fibroblasts from light ear mice display normal distribution and trafficking of the lysosomal membrane protein, Lamp-2, in contrast to fibroblasts from AP-3-deficient pearl mice (HPS2), which exhibit increased trafficking of this lysosomal protein via the plasma membrane. Similarly, light ear fibroblasts display an apparently normal accumulation of Zn2+ in intracellular vesicles, unlike pearl fibroblasts, which exhibit a decreased intracellular Zn2+ storage. Taken together, these observations demonstrate that the HPS1 and HPS4 proteins are components of a cytosolic complex that is involved in the biogenesis of lysosomal-related organelles by a mechanism distinct from that operated by AP-3 complex.