Graduate Program in Chinese Academy of Medical Sciences and Peking Union Medical College, China.
Science. 2012 Jul 20;337(6092):351-4. doi: 10.1126/science.1220281.
Defective catabolite export from lysosomes results in lysosomal storage diseases in humans. Mutations in the cystine transporter gene CTNS cause cystinosis, but other lysosomal amino acid transporters are poorly characterized at the molecular level. Here, we identified the Caenorhabditis elegans lysosomal lysine/arginine transporter LAAT-1. Loss of laat-1 caused accumulation of lysine and arginine in enlarged, degradation-defective lysosomes. In mutants of ctns-1 (C. elegans homolog of CTNS), LAAT-1 was required to reduce lysosomal cystine levels and suppress lysosome enlargement by cysteamine, a drug that alleviates cystinosis by converting cystine to a lysine analog. LAAT-1 also maintained availability of cytosolic lysine/arginine during embryogenesis. Thus, LAAT-1 is the lysosomal lysine/arginine transporter, which suggests a molecular explanation for how cysteamine alleviates a lysosomal storage disease.
溶酶体中分解代谢产物的输出缺陷导致人类溶酶体贮积症。胱氨酸转运蛋白基因 CTNS 的突变导致胱氨酸贮积症，但其他溶酶体氨基酸转运蛋白在分子水平上的特征描述较差。在这里，我们鉴定了秀丽隐杆线虫溶酶体赖氨酸/精氨酸转运蛋白 LAAT-1。laat-1 的缺失导致赖氨酸和精氨酸在增大的、降解缺陷的溶酶体中积累。在 ctns-1（CTNS 的秀丽隐杆线虫同源物）突变体中，LAAT-1 是降低溶酶体胱氨酸水平和抑制半胱胺引起的溶酶体增大所必需的，半胱胺通过将胱氨酸转化为赖氨酸类似物来缓解胱氨酸贮积症。LAAT-1 还在胚胎发生过程中维持细胞质中赖氨酸/精氨酸的可用性。因此，LAAT-1 是溶酶体赖氨酸/精氨酸转运蛋白，这为半胱胺如何缓解溶酶体贮积症提供了分子解释。
