Two motifs target Batten disease protein CLN3 to lysosomes in transfected nonneuronal and neuronal cells
Two motifs target Batten disease protein CLN3 to lysosomes in transfected nonneuronal and neuronal cells
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DOI：
10.1091/mbc.e03-02-0120
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发表时间：
2004-03-01
影响因子：
3.3
通讯作者：
Luzio, JP
中科院分区：
文献类型：
--
作者：
Kyttälä, A;Ihrke, G;Luzio, JP
Batten 病是一种由 CLN3 突变引起的神经退行性疾病，CLN3 是一种多胞膜蛋白，其在非神经元细胞中的主要细胞内目的地是溶酶体。 CLN3 蛋白的拓扑结构、其溶酶体靶向机制以及 Batten 病的发展尚不清楚。我们提供的实验证据表明 CLN3 的 N 端和 C 端以及一个大环结构域都面向细胞质。我们已经鉴定出两种介导转染的非神经元和神经元细胞中 CLN3 分选的溶酶体靶向基序：长 C 端胞质尾中的非常规基序，由由 9 个氨基酸 [M(X)(9)G] 分隔的甲硫氨酸和甘氨酸组成，以及更传统的二亮氨酸基序，位于大胞质环结构域中，前面有一个酸性斑块。每个基序本身足以介导溶酶体靶向，但最佳效率需要两者兼而有之。有趣的是，在原代神经元中，CLN3 在细胞体的溶酶体和内体中都明显可见，沿着神经元过程含有早期内体抗原 1。由于轴突和树突周围部分的溶酶体很少，因此神经元内体中 CLN3 的存在可能具有重要的功能。蛋白质的内体关联独立于两个溶酶体靶向基序。
Batten disease is a neurodegenerative disorder resulting from mutations in CLN3, a polytopic membrane protein, whose predominant intracellular destination in nonneuronal cells is the lysosome. The topology of CLN3 protein, its lysosomal targeting mechanism, and the development of Batten disease are poorly understood. We provide experimental evidence that both the N and C termini and one large loop domain of CLN3 face the cytoplasm. We have identified two lysosomal targeting motifs that mediate the sorting of CLN3 in transfected nonneuronal and neuronal cells: an unconventional motif in the long C-terminal cytosolic tail consisting of a methionine and a glycine separated by nine amino acids [M(X)(9)G], and a more conventional dileucine motif, located in the large cytosolic loop domain and preceded by an acidic patch. Each motif on its own was sufficient to mediate lysosomal targeting, but optimal efficiency required both. Interestingly, in primary neurons, CLN3 was prominently seen both in lysosomes in the cell body and in endosomes, containing early endosomal antigen-1 along neuronal processes. Because there are few lysosomes in axons and peripheral parts of dendrites, the presence of CLN3 in endosomes of neurons may be functionally important. Endosomal association of the protein was independent of the two lysosomal targeting motifs.