Dictyostelium LvsB mutants model the lysosomal defects associated with Chediak-Higashi syndrome
Dictyostelium LvsB mutants model the lysosomal defects associated with Chediak-Higashi syndrome
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DOI：
10.1091/mbc.01-09-0454
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发表时间：
2002-02-01
影响因子：
3.3
通讯作者：
Cardelli, J
中科院分区：
文献类型：
--
作者：
Harris, E;Wang, N;Cardelli, J
Chediak-Higashi 综合征是一种遗传性疾病，由编码人类 LYST（“溶酶体运输调节因子”）或小鼠 Beige 蛋白质的基因突变引起。这种疾病的一个显着特征是多种细胞中溶酶体相关颗粒增大的积累。盘基网柄菌的基因组包含六个编码与 LYST/Beige 氨基酸序列相关的蛋白质的基因，其中一个基因 lvsA（大体积球体）的破坏会导致胞质分裂的严重缺陷。为了更好地了解该蛋白家族在膜运输中的功能，我们分析了 lvsA、lvsB、lvsC、lvsD、lvsE 和 lvsF 中被破坏的突变体。在所有这些中，只有 lvsA 和 lvsB 突变体在我们的测定中表现出有趣的表型。 lvsA 缺失细胞表现出吞噬作用缺陷，并含有看起来异常的收缩液泡膜。 LvsB（与 LYST/Beige 最相似的盘基网柄菌蛋白）的缺失导致形成增大的囊泡，根据多种标准，该囊泡似乎是酸性溶酶体。 lvsB 缺失细胞的内吞作用、吞噬作用和液相胞吐作用速率正常。此外，溶酶体α-甘露糖苷酶的加工速率和靶向效率是正常的，尽管lvsB突变体不能有效地保留α-甘露糖苷酶以及其他两种溶酶体半胱氨酸蛋白酶。最后，脉冲追踪实验的结果表明，融合率的增加是 lvsB 缺失细胞中溶酶体增大的原因，这表明 LvsB 充当融合的负调节因子。我们的结果支持这样的观点，即 LvsB/LYST/Beige 以类似的方式发挥调节溶酶体生物发生的作用。
Chediak-Higashi syndrome is a genetic disorder caused by mutations in a gene encoding a protein named LYST in humans ("lysosomal trafficking regulator") or Beige in mice. A prominent feature of this disease is the accumulation of enlarged lysosome-related granules in a variety of cells. The genome of Dictyostelium discoideum contains six genes encoding proteins that are related to LYST/Beige in amino acid sequence, and disruption of one of these genes, lvsA (large volume sphere), results in profound defects in cytokinesis. To better understand the function of this family of proteins in membrane trafficking, we have analyzed mutants disrupted in lvsA, lvsB, lvsC, lvsD, lvsE, and lvsF. Of all these, only lvsA and lvsB mutants displayed interesting phenotypes in our assays. lvsA-null cells exhibited defects in phagocytosis and contained abnormal looking contractile vacuole membranes. Loss of LvsB, the Dictyostelium protein most similar to LYST/Beige, resulted in the formation of enlarged vesicles that by multiple criteria appeared to be acidic lysosomes. The rates of endocytosis, phagocytosis, and fluid phase exocytosis were normal in lvsB-null cells. Also, the rates of processing and the efficiency of targeting of lysosomal alpha-mannosidase were normal, although lvsB mutants inefficiently retained a-mannosidase, as well as two other lysosomal cysteine proteinases. Finally, results of pulse-chase experiments indicated that an increase in fusion rates accounted for the enlarged lysosomes in lvsB-null cells, suggesting that LvsB acts as a negative regulator of fusion. Our results support the notion that LvsB/LYST/Beige function in a similar manner to regulate lysosome biogenesis.