Liao J, Price D, Omary M B
Clontech Laboratories Inc., Palo Alto, CA 94303, USA.
FEBS Lett. 1997 Nov 17;417(3):316-20. doi: 10.1016/s0014-5793(97)01315-x.
Keratin polypeptides 8 and 18 (K8/18) are intermediate filament proteins that are expressed in 'simple-type' epithelial cells. They associate with several proteins including the 70 kDa cytoplasmic heat shock proteins (hsp70). We identified the human 78 kDa glucose-regulated protein (grp78) as a keratin-associated protein. Keratin-grp78 association was noted after co-immunoprecipitation of K8/18 from HT29 detergent solubilized cell lysates, and appears to involve non-posttranslationally modified grp78. The grp78-K8/18 association is induced by culturing cells in the presence of tunicamycin or after glucose starvation. K8/18-bound grp78 can be dissociated by Mg-ATP and the association can be reconstituted in vitro using purified grp78, then redissociated again by Mg-ATP. Binding of grp78 occurs preferentially with K8, and when reconstituted does not depend on the posttranslational modification state of K8/18. Co-incubation of K8/18 with hsp70 and grp78 shows preferential association with hsp70. Our results demonstrate a direct association of grp78 with K8 under conditions that induce grp78 expression.
角蛋白多肽8和18（K8/18）是在“简单型”上皮细胞中表达的中间丝蛋白。它们与包括70 kDa细胞质热休克蛋白（hsp70）在内的多种蛋白质相关联。我们鉴定出人类78 kDa葡萄糖调节蛋白（grp78）为一种角蛋白相关蛋白。从HT29去污剂溶解的细胞裂解物中共免疫沉淀K8/18后，发现了角蛋白与grp78的关联，并且这种关联似乎涉及未经过翻译后修饰的grp78。grp78与K8/18的关联是通过在衣霉素存在下培养细胞或在葡萄糖饥饿后诱导产生的。与K8/18结合的grp78可以被Mg-ATP解离，并且这种关联可以在体外使用纯化的grp78进行重建，然后再次被Mg-ATP解离。grp78的结合优先发生在K8上，并且在重建时不依赖于K8/18的翻译后修饰状态。K8/18与hsp70和grp78共同孵育显示出与hsp70的优先关联。我们的结果证明了在诱导grp78表达的条件下，grp78与K8之间存在直接关联。
