hsc70 moderates the heat shock (stress) response in Xenopus laevis oocytes and binds to denatured protein inducers.
Injections of hsc70 protein into Xenopus oocytes lowered the stress response to both a thermal shock and to co-injected protein inducers. Binding of hsc70 to native and modified forms of bovine serum albumin (BSA) were tested by two assays. In one, nitrocellulose-bound proteins were incubated with hsc70, cross-linked with glutaraldehyde, and then bound hsc70 was probed with a monoclonal anti-hsc70 antibody. In the second, peroxidase-conjugated hsc70 was employed as a more direct probe for binding to proteins displayed on nitrocellulose membranes. hsc70 binding to the BSA derivatives correlated with their abilities to induce a stress response upon microinjection into oocytes. Reduced and carboxymethylated (rcm) BSA, the most potent stress inducer tested, was bound most tightly by hsc70, whereas hsc70 had moderate affinity for N-methylated rcm-BSA and very little affinity for the native protein. No binding was observed with iodinated BSA. The results suggest a mechanism whereby the cell employs hsc70 or other proteins of the hsp70 family both to trigger the response to an environmental stress and to provide a feedback mechanism to attenuate the response.
Mifflin
L C
LC
Department of Chemistry and Biochemistry, University of California, Los Angeles 90024.
Cohen
R E
RE
D000818:Animals; D003459:Crystallins / Q000494:pharmacology; D005260:Female; D006360:Heat-Shock Proteins / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology; D006706:Homeostasis; D006735:Horseradish Peroxidase / Q000302:isolation & purification / Q000378:metabolism; D006358:Hot Temperature; D066298:In Vitro Techniques; D007700:Kinetics; D008745:Methylation; D008954:Models, Biological; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D012710:Serum Albumin, Bovine / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology; D014982:Xenopus laevis
D003459:Crystallins; D006360:Heat-Shock Proteins; D012710:Serum Albumin, Bovine; D006735:Horseradish Peroxidase