Association of glucose-regulated protein (grp78) with human keratin 8.
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.
Liao
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Clontech Laboratories Inc., Palo Alto, CA 94303, USA.
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D000255:Adenosine Triphosphate / Q000494:pharmacology; D002352:Carrier Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D002453:Cell Cycle; D002460:Cell Line; D004591:Electrophoresis, Polyacrylamide Gel; D000091342:Endoplasmic Reticulum Chaperone BiP; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006360:Heat-Shock Proteins; D006801:Humans; D007633:Keratins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D018832:Molecular Chaperones / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D011485:Protein Binding
D002352:Carrier Proteins; D000091342:Endoplasmic Reticulum Chaperone BiP; D018840:HSP70 Heat-Shock Proteins; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D007633:Keratins; D000255:Adenosine Triphosphate