INTERACTION OF HEAT-STRESS GLYCOPROTEIN GP50 WITH CLASSICAL HEAT-SHOCK PROTEINS

Cellular stress conditions are known to elevate heat-shock protein (HS P) synthesis and protein glycosylation, leading to the development of cellular thermotolerance. In the present study, we investigated the in teraction of a major stress glycoprotein, GP50, with other cellular pr oteins during recovery from heat stress, using mostly immunoprecipitat ion techniques. Parallel studies of heat-stressed CHO and M21 cells sh owed that both glycosylated and unglycosylated forms of GP50 interact with several members of the classical HSP families (e.g., HSP70 and HS P90) in an ATP-dependent manner. The specificity of HSP-stress glycopr otein interactions was confirmed by chemical crosslinking with a homob ifunctional agent, 3,3'-dithiobis (succinimidyl propionate). Interacti on of GP50 with denatured proteins was also demonstrated through bindi ng to gelatin. Protein complexes formed between stress glycoproteins a nd HSPs were further characterized by gel filtration and showed an ave rage molecular mass between 400 and 600 kDa. Overall, the consistent a ssociation of stress glycoproteins with nonglycosylated HSPs suggests a structural/functional role for protein chaperone complexes that cons ist of denatured proteins and the glycone/aglycone elements of cellula r stress response. (C) 1998 Academic Press.