Uthayakumar S, Granger B L
Veterinary Molecular Biology Laboratory, Montana State University, Bozeman 59717, USA.
Cell Mol Biol Res. 1995;41(5):405-20.
We cloned and sequenced cDNAs encoding two lysosomal membrane glycoproteins, lgp-A and lgp-B, from Chinese hamster ovary cells. The deduced amino acid sequences of these proteins are similar to those of the other known members of this conserved family (also known as "LAMP" proteins). We used the cDNAs to generate stable lines of hamster lgp-expressing mouse NIH-3T3 cells, rat NRK cells, and monkey CV-1 cells. We also generated hybridomas that secrete antibodies specific for hamster lgp-A and lgp-B, enabling us to distinguish foreign from endogenous lgps in a wider variety of transfected cell lines. One line of mouse NIH-3T3 cells that expresses hamster lgp-B was studied in detail. Whereas most of the hamster lgp-B appeared to be transported to lysosomes in these cells, butyrate-induced overexpression resulted in the accumulation of a significant proportion of the total on the plasma membrane. In addition, overexpression of this foreign lgp-B also resulted in the appearance of the endogenous mouse lgp-A and lgp-B on the plasma membrane. Characterization of this accumulation suggested that it resulted from competition for one or more limited components in the transport pathway(s) to lysosomes. Endocytosis from the plasma membrane appeared to be one step that was saturable.
我们从中国仓鼠卵巢细胞中克隆并测序了编码两种溶酶体膜糖蛋白lgp - A和lgp - B的cDNA。这些蛋白质的推导氨基酸序列与这个保守家族（也称为“LAMP”蛋白）的其他已知成员相似。我们用这些cDNA在仓鼠lgp表达的小鼠NIH - 3T3细胞、大鼠NRK细胞和猴CV - 1细胞中产生了稳定细胞系。我们还制备了分泌针对仓鼠lgp - A和lgp - B的特异性抗体的杂交瘤，这使我们能够在更多种类的转染细胞系中区分外源lgp和内源lgp。对一个表达仓鼠lgp - B的小鼠NIH - 3T3细胞系进行了详细研究。在这些细胞中，大部分仓鼠lgp - B似乎被转运到溶酶体中，但丁酸盐诱导的过表达导致相当比例的总量积聚在质膜上。此外，这种外源lgp - B的过表达还导致内源小鼠lgp - A和lgp - B出现在质膜上。对这种积聚的特征分析表明，它是由在向溶酶体的转运途径中对一种或多种有限成分的竞争导致的。从质膜的内吞作用似乎是一个可饱和的步骤。
