Gahl W A, Bernardini I, Tietze F, Kohn L D
Section on Human Biochemical Genetics, National Institute of Child Health and Human Development, Bethesda, Maryland 20892.
Biochem Med Metab Biol. 1993 Apr;49(2):243-54. doi: 10.1006/bmmb.1993.1026.
Rat thyroid FRTL-5 cells were employed to study the synthesis and degradation of a functional integral lysosomal membrane protein, the lysosomal cystine transporter. This carrier exhibited countertransport and closely resembled the cystine transport system of human leucocytes, fibroblasts, and lymphoblasts shown to be defective in the lysosomal storage disease, nephropathic cystinosis. Using cycloheximide to prevent new protein synthesis, the half-life of the FRTL-5 cell lysosomal cystine carrier was determined to approximate 21 h. Carrier function was not influenced by the N-glycosylation inhibitor tunicamycin, nor by the oligosaccharide processing inhibitors castanospermine and deoxymannojirimycin. The data suggest that the lysosomal cystine carrier is a protein without strict functional requirements for N-linked oligosaccharides, and that rat FRTL-5 cells can be employed in future investigations into the structure and function of other integral lysosomal membrane proteins as well.
采用大鼠甲状腺FRTL-5细胞来研究一种功能性完整溶酶体膜蛋白——溶酶体胱氨酸转运体的合成与降解。这种载体表现出反向转运，并且与人类白细胞、成纤维细胞和淋巴母细胞的胱氨酸转运系统极为相似，而这些细胞的胱氨酸转运系统在溶酶体贮积病——肾病性胱氨酸病中被证明存在缺陷。使用环己酰亚胺来阻止新蛋白质的合成，测定出FRTL-5细胞溶酶体胱氨酸载体的半衰期约为21小时。载体功能不受N-糖基化抑制剂衣霉素的影响，也不受寡糖加工抑制剂蓖麻毒蛋白和脱氧甘露基野尻霉素的影响。这些数据表明，溶酶体胱氨酸载体是一种对N-连接寡糖没有严格功能要求的蛋白质，并且大鼠FRTL-5细胞也可用于未来对其他完整溶酶体膜蛋白的结构和功能的研究。
